From 4e376cc104bc45e9dcac04374e21b5e8b976d282 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sun, 29 Oct 2023 10:13:07 +0100 Subject: [PATCH 1/7] Test empty types better --- ...tch-check-notes.exhaustive_patterns.stderr | 63 ++ .../empty-match-check-notes.normal.stderr | 62 ++ .../usefulness/empty-match-check-notes.rs | 52 ++ .../empty-match.exhaustive_patterns.stderr | 284 +++---- .../usefulness/empty-match.normal.stderr | 283 +++---- tests/ui/pattern/usefulness/empty-match.rs | 178 +--- .../empty-types.exhaustive_patterns.stderr | 776 ++++++++++++++++++ .../usefulness/empty-types.normal.stderr | 721 ++++++++++++++++ tests/ui/pattern/usefulness/empty-types.rs | 665 +++++++++++++++ tests/ui/uninhabited/uninhabited-patterns.rs | 12 +- .../uninhabited/uninhabited-patterns.stderr | 12 +- 11 files changed, 2606 insertions(+), 502 deletions(-) create mode 100644 tests/ui/pattern/usefulness/empty-match-check-notes.exhaustive_patterns.stderr create mode 100644 tests/ui/pattern/usefulness/empty-match-check-notes.normal.stderr create mode 100644 tests/ui/pattern/usefulness/empty-match-check-notes.rs create mode 100644 tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr create mode 100644 tests/ui/pattern/usefulness/empty-types.normal.stderr create mode 100644 tests/ui/pattern/usefulness/empty-types.rs diff --git a/tests/ui/pattern/usefulness/empty-match-check-notes.exhaustive_patterns.stderr b/tests/ui/pattern/usefulness/empty-match-check-notes.exhaustive_patterns.stderr new file mode 100644 index 0000000000000..304435cb21e8a --- /dev/null +++ b/tests/ui/pattern/usefulness/empty-match-check-notes.exhaustive_patterns.stderr @@ -0,0 +1,63 @@ +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:17:9 + | +LL | _ => {} + | ^ + | +note: the lint level is defined here + --> $DIR/empty-match-check-notes.rs:7:9 + | +LL | #![deny(unreachable_patterns)] + | ^^^^^^^^^^^^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:20:9 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:27:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:30:9 + | +LL | _ if false => {} + | ^ + +error[E0005]: refutable pattern in local binding + --> $DIR/empty-match-check-notes.rs:35:9 + | +LL | let None = x; + | ^^^^ pattern `Some(_)` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: pattern `Some(_)` is currently uninhabited, but this variant contains private fields which may become inhabited in the future + = note: the matched value is of type `Option` +help: you might want to use `if let` to ignore the variant that isn't matched + | +LL | if let None = x { todo!() }; + | ++ +++++++++++ + +error[E0004]: non-exhaustive patterns: `_` not covered + --> $DIR/empty-match-check-notes.rs:45:11 + | +LL | match 0u8 { + | ^^^ pattern `_` not covered + | + = note: the matched value is of type `u8` + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ _ if false => {}, +LL + _ => todo!() + | + +error: aborting due to 6 previous errors + +Some errors have detailed explanations: E0004, E0005. +For more information about an error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-match-check-notes.normal.stderr b/tests/ui/pattern/usefulness/empty-match-check-notes.normal.stderr new file mode 100644 index 0000000000000..40494b726f00c --- /dev/null +++ b/tests/ui/pattern/usefulness/empty-match-check-notes.normal.stderr @@ -0,0 +1,62 @@ +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:17:9 + | +LL | _ => {} + | ^ + | +note: the lint level is defined here + --> $DIR/empty-match-check-notes.rs:7:9 + | +LL | #![deny(unreachable_patterns)] + | ^^^^^^^^^^^^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:20:9 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:27:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-match-check-notes.rs:30:9 + | +LL | _ if false => {} + | ^ + +error[E0005]: refutable pattern in local binding + --> $DIR/empty-match-check-notes.rs:35:9 + | +LL | let None = x; + | ^^^^ pattern `Some(_)` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: the matched value is of type `Option` +help: you might want to use `if let` to ignore the variant that isn't matched + | +LL | if let None = x { todo!() }; + | ++ +++++++++++ + +error[E0004]: non-exhaustive patterns: `_` not covered + --> $DIR/empty-match-check-notes.rs:45:11 + | +LL | match 0u8 { + | ^^^ pattern `_` not covered + | + = note: the matched value is of type `u8` + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ _ if false => {}, +LL + _ => todo!() + | + +error: aborting due to 6 previous errors + +Some errors have detailed explanations: E0004, E0005. +For more information about an error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-match-check-notes.rs b/tests/ui/pattern/usefulness/empty-match-check-notes.rs new file mode 100644 index 0000000000000..ee9ff3dcf9012 --- /dev/null +++ b/tests/ui/pattern/usefulness/empty-match-check-notes.rs @@ -0,0 +1,52 @@ +// aux-build:empty.rs +// revisions: normal exhaustive_patterns +// +// This tests a match with no arms on various types, and checks NOTEs. +#![feature(never_type)] +#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))] +#![deny(unreachable_patterns)] +//~^ NOTE the lint level is defined here + +extern crate empty; + +enum EmptyEnum {} + +fn empty_enum(x: EmptyEnum) { + match x {} // ok + match x { + _ => {} //~ ERROR unreachable pattern + } + match x { + _ if false => {} //~ ERROR unreachable pattern + } +} + +fn empty_foreign_enum(x: empty::EmptyForeignEnum) { + match x {} // ok + match x { + _ => {} //~ ERROR unreachable pattern + } + match x { + _ if false => {} //~ ERROR unreachable pattern + } +} + +fn empty_foreign_enum_private(x: Option) { + let None = x; + //~^ ERROR refutable pattern in local binding + //~| NOTE `let` bindings require an "irrefutable pattern" + //~| NOTE for more information, visit + //~| NOTE the matched value is of type + //~| NOTE pattern `Some(_)` not covered + //[exhaustive_patterns]~| NOTE currently uninhabited, but this variant contains private fields +} + +fn main() { + match 0u8 { + //~^ ERROR `_` not covered + //~| NOTE the matched value is of type + //~| NOTE match arms with guards don't count towards exhaustivity + //~| NOTE pattern `_` not covered + _ if false => {} + } +} diff --git a/tests/ui/pattern/usefulness/empty-match.exhaustive_patterns.stderr b/tests/ui/pattern/usefulness/empty-match.exhaustive_patterns.stderr index 8f9bd5bde89aa..9c3bebd7797b8 100644 --- a/tests/ui/pattern/usefulness/empty-match.exhaustive_patterns.stderr +++ b/tests/ui/pattern/usefulness/empty-match.exhaustive_patterns.stderr @@ -1,62 +1,5 @@ -error: unreachable pattern - --> $DIR/empty-match.rs:68:9 - | -LL | _ => {}, - | ^ - | -note: the lint level is defined here - --> $DIR/empty-match.rs:8:9 - | -LL | #![deny(unreachable_patterns)] - | ^^^^^^^^^^^^^^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-match.rs:71:9 - | -LL | _ if false => {}, - | ^ - -error: unreachable pattern - --> $DIR/empty-match.rs:78:9 - | -LL | _ => {}, - | ^ - -error: unreachable pattern - --> $DIR/empty-match.rs:81:9 - | -LL | _ if false => {}, - | ^ - -error[E0005]: refutable pattern in local binding - --> $DIR/empty-match.rs:86:9 - | -LL | let None = x; - | ^^^^ pattern `Some(_)` not covered - | - = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant - = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html - = note: pattern `Some(_)` is currently uninhabited, but this variant contains private fields which may become inhabited in the future - = note: the matched value is of type `Option` -help: you might want to use `if let` to ignore the variant that isn't matched - | -LL | if let None = x { todo!() }; - | ++ +++++++++++ - -error: unreachable pattern - --> $DIR/empty-match.rs:98:9 - | -LL | _ => {}, - | ^ - -error: unreachable pattern - --> $DIR/empty-match.rs:101:9 - | -LL | _ if false => {}, - | ^ - error[E0004]: non-exhaustive patterns: type `u8` is non-empty - --> $DIR/empty-match.rs:119:20 + --> $DIR/empty-match.rs:46:20 | LL | match_no_arms!(0u8); | ^^^ @@ -65,122 +8,121 @@ LL | match_no_arms!(0u8); = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyStruct1` is non-empty - --> $DIR/empty-match.rs:121:20 + --> $DIR/empty-match.rs:47:20 | LL | match_no_arms!(NonEmptyStruct1); | ^^^^^^^^^^^^^^^ | note: `NonEmptyStruct1` defined here - --> $DIR/empty-match.rs:15:8 + --> $DIR/empty-match.rs:22:12 | -LL | struct NonEmptyStruct1; - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct1; + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct1` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyStruct2` is non-empty - --> $DIR/empty-match.rs:123:20 + --> $DIR/empty-match.rs:48:20 | LL | match_no_arms!(NonEmptyStruct2(true)); | ^^^^^^^^^^^^^^^^^^^^^ | note: `NonEmptyStruct2` defined here - --> $DIR/empty-match.rs:18:8 + --> $DIR/empty-match.rs:23:12 | -LL | struct NonEmptyStruct2(bool); - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct2(bool); + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct2` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyUnion1` is non-empty - --> $DIR/empty-match.rs:125:20 + --> $DIR/empty-match.rs:49:20 | LL | match_no_arms!((NonEmptyUnion1 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | note: `NonEmptyUnion1` defined here - --> $DIR/empty-match.rs:21:7 + --> $DIR/empty-match.rs:24:11 | -LL | union NonEmptyUnion1 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion1 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion1` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyUnion2` is non-empty - --> $DIR/empty-match.rs:127:20 + --> $DIR/empty-match.rs:50:20 | LL | match_no_arms!((NonEmptyUnion2 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | note: `NonEmptyUnion2` defined here - --> $DIR/empty-match.rs:26:7 + --> $DIR/empty-match.rs:27:11 | -LL | union NonEmptyUnion2 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion2 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion2` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: `NonEmptyEnum1::Foo(_)` not covered - --> $DIR/empty-match.rs:129:20 + --> $DIR/empty-match.rs:51:20 | LL | match_no_arms!(NonEmptyEnum1::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered | note: `NonEmptyEnum1` defined here - --> $DIR/empty-match.rs:32:6 + --> $DIR/empty-match.rs:31:10 | -LL | enum NonEmptyEnum1 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered +LL | enum NonEmptyEnum1 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered = note: the matched value is of type `NonEmptyEnum1` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern error[E0004]: non-exhaustive patterns: `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered - --> $DIR/empty-match.rs:132:20 + --> $DIR/empty-match.rs:52:20 | LL | match_no_arms!(NonEmptyEnum2::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered | note: `NonEmptyEnum2` defined here - --> $DIR/empty-match.rs:39:6 - | -LL | enum NonEmptyEnum2 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered -... -LL | Bar, - | --- not covered + --> $DIR/empty-match.rs:34:10 + | +LL | enum NonEmptyEnum2 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered +LL | Bar, + | --- not covered = note: the matched value is of type `NonEmptyEnum2` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or multiple match arms error[E0004]: non-exhaustive patterns: `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered - --> $DIR/empty-match.rs:135:20 + --> $DIR/empty-match.rs:53:20 | LL | match_no_arms!(NonEmptyEnum5::V1); | ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered | note: `NonEmptyEnum5` defined here - --> $DIR/empty-match.rs:49:6 - | -LL | enum NonEmptyEnum5 { - | ^^^^^^^^^^^^^ -... -LL | V1, V2, V3, V4, V5, - | -- -- -- -- -- not covered - | | | | | - | | | | not covered - | | | not covered - | | not covered - | not covered + --> $DIR/empty-match.rs:38:10 + | +LL | enum NonEmptyEnum5 { + | ^^^^^^^^^^^^^ +LL | V1, + | -- not covered +LL | V2, + | -- not covered +LL | V3, + | -- not covered +LL | V4, + | -- not covered +LL | V5, + | -- not covered = note: the matched value is of type `NonEmptyEnum5` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or multiple match arms error[E0004]: non-exhaustive patterns: `_` not covered - --> $DIR/empty-match.rs:139:24 + --> $DIR/empty-match.rs:55:24 | LL | match_guarded_arm!(0u8); | ^^^ pattern `_` not covered @@ -189,161 +131,159 @@ LL | match_guarded_arm!(0u8); = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + _ => todo!() +LL ~ _ if false => {}, +LL + _ => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyStruct1` not covered - --> $DIR/empty-match.rs:144:24 + --> $DIR/empty-match.rs:56:24 | LL | match_guarded_arm!(NonEmptyStruct1); | ^^^^^^^^^^^^^^^ pattern `NonEmptyStruct1` not covered | note: `NonEmptyStruct1` defined here - --> $DIR/empty-match.rs:15:8 + --> $DIR/empty-match.rs:22:12 | -LL | struct NonEmptyStruct1; - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct1; + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct1` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyStruct1 => todo!() +LL ~ _ if false => {}, +LL + NonEmptyStruct1 => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyStruct2(_)` not covered - --> $DIR/empty-match.rs:149:24 + --> $DIR/empty-match.rs:57:24 | LL | match_guarded_arm!(NonEmptyStruct2(true)); | ^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyStruct2(_)` not covered | note: `NonEmptyStruct2` defined here - --> $DIR/empty-match.rs:18:8 + --> $DIR/empty-match.rs:23:12 | -LL | struct NonEmptyStruct2(bool); - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct2(bool); + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct2` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyStruct2(_) => todo!() +LL ~ _ if false => {}, +LL + NonEmptyStruct2(_) => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyUnion1 { .. }` not covered - --> $DIR/empty-match.rs:154:24 + --> $DIR/empty-match.rs:58:24 | LL | match_guarded_arm!((NonEmptyUnion1 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion1 { .. }` not covered | note: `NonEmptyUnion1` defined here - --> $DIR/empty-match.rs:21:7 + --> $DIR/empty-match.rs:24:11 | -LL | union NonEmptyUnion1 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion1 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion1` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyUnion1 { .. } => todo!() +LL ~ _ if false => {}, +LL + NonEmptyUnion1 { .. } => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyUnion2 { .. }` not covered - --> $DIR/empty-match.rs:159:24 + --> $DIR/empty-match.rs:59:24 | LL | match_guarded_arm!((NonEmptyUnion2 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion2 { .. }` not covered | note: `NonEmptyUnion2` defined here - --> $DIR/empty-match.rs:26:7 + --> $DIR/empty-match.rs:27:11 | -LL | union NonEmptyUnion2 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion2 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion2` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyUnion2 { .. } => todo!() +LL ~ _ if false => {}, +LL + NonEmptyUnion2 { .. } => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyEnum1::Foo(_)` not covered - --> $DIR/empty-match.rs:164:24 + --> $DIR/empty-match.rs:60:24 | LL | match_guarded_arm!(NonEmptyEnum1::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered | note: `NonEmptyEnum1` defined here - --> $DIR/empty-match.rs:32:6 + --> $DIR/empty-match.rs:31:10 | -LL | enum NonEmptyEnum1 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered +LL | enum NonEmptyEnum1 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered = note: the matched value is of type `NonEmptyEnum1` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyEnum1::Foo(_) => todo!() +LL ~ _ if false => {}, +LL + NonEmptyEnum1::Foo(_) => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered - --> $DIR/empty-match.rs:169:24 + --> $DIR/empty-match.rs:61:24 | LL | match_guarded_arm!(NonEmptyEnum2::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered | note: `NonEmptyEnum2` defined here - --> $DIR/empty-match.rs:39:6 - | -LL | enum NonEmptyEnum2 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered -... -LL | Bar, - | --- not covered + --> $DIR/empty-match.rs:34:10 + | +LL | enum NonEmptyEnum2 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered +LL | Bar, + | --- not covered = note: the matched value is of type `NonEmptyEnum2` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms | -LL ~ _ if false => {}, -LL + NonEmptyEnum2::Foo(_) | NonEmptyEnum2::Bar => todo!() +LL ~ _ if false => {}, +LL + NonEmptyEnum2::Foo(_) | NonEmptyEnum2::Bar => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered - --> $DIR/empty-match.rs:174:24 + --> $DIR/empty-match.rs:62:24 | LL | match_guarded_arm!(NonEmptyEnum5::V1); | ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered | note: `NonEmptyEnum5` defined here - --> $DIR/empty-match.rs:49:6 - | -LL | enum NonEmptyEnum5 { - | ^^^^^^^^^^^^^ -... -LL | V1, V2, V3, V4, V5, - | -- -- -- -- -- not covered - | | | | | - | | | | not covered - | | | not covered - | | not covered - | not covered + --> $DIR/empty-match.rs:38:10 + | +LL | enum NonEmptyEnum5 { + | ^^^^^^^^^^^^^ +LL | V1, + | -- not covered +LL | V2, + | -- not covered +LL | V3, + | -- not covered +LL | V4, + | -- not covered +LL | V5, + | -- not covered = note: the matched value is of type `NonEmptyEnum5` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown, or multiple match arms | -LL ~ _ if false => {}, -LL + _ => todo!() +LL ~ _ if false => {}, +LL + _ => todo!() | -error: aborting due to 23 previous errors +error: aborting due to 16 previous errors -Some errors have detailed explanations: E0004, E0005. -For more information about an error, try `rustc --explain E0004`. +For more information about this error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-match.normal.stderr b/tests/ui/pattern/usefulness/empty-match.normal.stderr index 7f0389f40e233..9c3bebd7797b8 100644 --- a/tests/ui/pattern/usefulness/empty-match.normal.stderr +++ b/tests/ui/pattern/usefulness/empty-match.normal.stderr @@ -1,61 +1,5 @@ -error: unreachable pattern - --> $DIR/empty-match.rs:68:9 - | -LL | _ => {}, - | ^ - | -note: the lint level is defined here - --> $DIR/empty-match.rs:8:9 - | -LL | #![deny(unreachable_patterns)] - | ^^^^^^^^^^^^^^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-match.rs:71:9 - | -LL | _ if false => {}, - | ^ - -error: unreachable pattern - --> $DIR/empty-match.rs:78:9 - | -LL | _ => {}, - | ^ - -error: unreachable pattern - --> $DIR/empty-match.rs:81:9 - | -LL | _ if false => {}, - | ^ - -error[E0005]: refutable pattern in local binding - --> $DIR/empty-match.rs:86:9 - | -LL | let None = x; - | ^^^^ pattern `Some(_)` not covered - | - = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant - = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html - = note: the matched value is of type `Option` -help: you might want to use `if let` to ignore the variant that isn't matched - | -LL | if let None = x { todo!() }; - | ++ +++++++++++ - -error: unreachable pattern - --> $DIR/empty-match.rs:98:9 - | -LL | _ => {}, - | ^ - -error: unreachable pattern - --> $DIR/empty-match.rs:101:9 - | -LL | _ if false => {}, - | ^ - error[E0004]: non-exhaustive patterns: type `u8` is non-empty - --> $DIR/empty-match.rs:119:20 + --> $DIR/empty-match.rs:46:20 | LL | match_no_arms!(0u8); | ^^^ @@ -64,122 +8,121 @@ LL | match_no_arms!(0u8); = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyStruct1` is non-empty - --> $DIR/empty-match.rs:121:20 + --> $DIR/empty-match.rs:47:20 | LL | match_no_arms!(NonEmptyStruct1); | ^^^^^^^^^^^^^^^ | note: `NonEmptyStruct1` defined here - --> $DIR/empty-match.rs:15:8 + --> $DIR/empty-match.rs:22:12 | -LL | struct NonEmptyStruct1; - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct1; + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct1` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyStruct2` is non-empty - --> $DIR/empty-match.rs:123:20 + --> $DIR/empty-match.rs:48:20 | LL | match_no_arms!(NonEmptyStruct2(true)); | ^^^^^^^^^^^^^^^^^^^^^ | note: `NonEmptyStruct2` defined here - --> $DIR/empty-match.rs:18:8 + --> $DIR/empty-match.rs:23:12 | -LL | struct NonEmptyStruct2(bool); - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct2(bool); + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct2` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyUnion1` is non-empty - --> $DIR/empty-match.rs:125:20 + --> $DIR/empty-match.rs:49:20 | LL | match_no_arms!((NonEmptyUnion1 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | note: `NonEmptyUnion1` defined here - --> $DIR/empty-match.rs:21:7 + --> $DIR/empty-match.rs:24:11 | -LL | union NonEmptyUnion1 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion1 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion1` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: type `NonEmptyUnion2` is non-empty - --> $DIR/empty-match.rs:127:20 + --> $DIR/empty-match.rs:50:20 | LL | match_no_arms!((NonEmptyUnion2 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | note: `NonEmptyUnion2` defined here - --> $DIR/empty-match.rs:26:7 + --> $DIR/empty-match.rs:27:11 | -LL | union NonEmptyUnion2 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion2 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion2` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern error[E0004]: non-exhaustive patterns: `NonEmptyEnum1::Foo(_)` not covered - --> $DIR/empty-match.rs:129:20 + --> $DIR/empty-match.rs:51:20 | LL | match_no_arms!(NonEmptyEnum1::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered | note: `NonEmptyEnum1` defined here - --> $DIR/empty-match.rs:32:6 + --> $DIR/empty-match.rs:31:10 | -LL | enum NonEmptyEnum1 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered +LL | enum NonEmptyEnum1 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered = note: the matched value is of type `NonEmptyEnum1` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern error[E0004]: non-exhaustive patterns: `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered - --> $DIR/empty-match.rs:132:20 + --> $DIR/empty-match.rs:52:20 | LL | match_no_arms!(NonEmptyEnum2::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered | note: `NonEmptyEnum2` defined here - --> $DIR/empty-match.rs:39:6 - | -LL | enum NonEmptyEnum2 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered -... -LL | Bar, - | --- not covered + --> $DIR/empty-match.rs:34:10 + | +LL | enum NonEmptyEnum2 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered +LL | Bar, + | --- not covered = note: the matched value is of type `NonEmptyEnum2` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or multiple match arms error[E0004]: non-exhaustive patterns: `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered - --> $DIR/empty-match.rs:135:20 + --> $DIR/empty-match.rs:53:20 | LL | match_no_arms!(NonEmptyEnum5::V1); | ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered | note: `NonEmptyEnum5` defined here - --> $DIR/empty-match.rs:49:6 - | -LL | enum NonEmptyEnum5 { - | ^^^^^^^^^^^^^ -... -LL | V1, V2, V3, V4, V5, - | -- -- -- -- -- not covered - | | | | | - | | | | not covered - | | | not covered - | | not covered - | not covered + --> $DIR/empty-match.rs:38:10 + | +LL | enum NonEmptyEnum5 { + | ^^^^^^^^^^^^^ +LL | V1, + | -- not covered +LL | V2, + | -- not covered +LL | V3, + | -- not covered +LL | V4, + | -- not covered +LL | V5, + | -- not covered = note: the matched value is of type `NonEmptyEnum5` = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or multiple match arms error[E0004]: non-exhaustive patterns: `_` not covered - --> $DIR/empty-match.rs:139:24 + --> $DIR/empty-match.rs:55:24 | LL | match_guarded_arm!(0u8); | ^^^ pattern `_` not covered @@ -188,161 +131,159 @@ LL | match_guarded_arm!(0u8); = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + _ => todo!() +LL ~ _ if false => {}, +LL + _ => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyStruct1` not covered - --> $DIR/empty-match.rs:144:24 + --> $DIR/empty-match.rs:56:24 | LL | match_guarded_arm!(NonEmptyStruct1); | ^^^^^^^^^^^^^^^ pattern `NonEmptyStruct1` not covered | note: `NonEmptyStruct1` defined here - --> $DIR/empty-match.rs:15:8 + --> $DIR/empty-match.rs:22:12 | -LL | struct NonEmptyStruct1; - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct1; + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct1` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyStruct1 => todo!() +LL ~ _ if false => {}, +LL + NonEmptyStruct1 => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyStruct2(_)` not covered - --> $DIR/empty-match.rs:149:24 + --> $DIR/empty-match.rs:57:24 | LL | match_guarded_arm!(NonEmptyStruct2(true)); | ^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyStruct2(_)` not covered | note: `NonEmptyStruct2` defined here - --> $DIR/empty-match.rs:18:8 + --> $DIR/empty-match.rs:23:12 | -LL | struct NonEmptyStruct2(bool); - | ^^^^^^^^^^^^^^^ +LL | struct NonEmptyStruct2(bool); + | ^^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyStruct2` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyStruct2(_) => todo!() +LL ~ _ if false => {}, +LL + NonEmptyStruct2(_) => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyUnion1 { .. }` not covered - --> $DIR/empty-match.rs:154:24 + --> $DIR/empty-match.rs:58:24 | LL | match_guarded_arm!((NonEmptyUnion1 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion1 { .. }` not covered | note: `NonEmptyUnion1` defined here - --> $DIR/empty-match.rs:21:7 + --> $DIR/empty-match.rs:24:11 | -LL | union NonEmptyUnion1 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion1 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion1` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyUnion1 { .. } => todo!() +LL ~ _ if false => {}, +LL + NonEmptyUnion1 { .. } => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyUnion2 { .. }` not covered - --> $DIR/empty-match.rs:159:24 + --> $DIR/empty-match.rs:59:24 | LL | match_guarded_arm!((NonEmptyUnion2 { foo: () })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion2 { .. }` not covered | note: `NonEmptyUnion2` defined here - --> $DIR/empty-match.rs:26:7 + --> $DIR/empty-match.rs:27:11 | -LL | union NonEmptyUnion2 { - | ^^^^^^^^^^^^^^ +LL | union NonEmptyUnion2 { + | ^^^^^^^^^^^^^^ = note: the matched value is of type `NonEmptyUnion2` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyUnion2 { .. } => todo!() +LL ~ _ if false => {}, +LL + NonEmptyUnion2 { .. } => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyEnum1::Foo(_)` not covered - --> $DIR/empty-match.rs:164:24 + --> $DIR/empty-match.rs:60:24 | LL | match_guarded_arm!(NonEmptyEnum1::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered | note: `NonEmptyEnum1` defined here - --> $DIR/empty-match.rs:32:6 + --> $DIR/empty-match.rs:31:10 | -LL | enum NonEmptyEnum1 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered +LL | enum NonEmptyEnum1 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered = note: the matched value is of type `NonEmptyEnum1` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL ~ _ if false => {}, -LL + NonEmptyEnum1::Foo(_) => todo!() +LL ~ _ if false => {}, +LL + NonEmptyEnum1::Foo(_) => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered - --> $DIR/empty-match.rs:169:24 + --> $DIR/empty-match.rs:61:24 | LL | match_guarded_arm!(NonEmptyEnum2::Foo(true)); | ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered | note: `NonEmptyEnum2` defined here - --> $DIR/empty-match.rs:39:6 - | -LL | enum NonEmptyEnum2 { - | ^^^^^^^^^^^^^ -... -LL | Foo(bool), - | --- not covered -... -LL | Bar, - | --- not covered + --> $DIR/empty-match.rs:34:10 + | +LL | enum NonEmptyEnum2 { + | ^^^^^^^^^^^^^ +LL | Foo(bool), + | --- not covered +LL | Bar, + | --- not covered = note: the matched value is of type `NonEmptyEnum2` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms | -LL ~ _ if false => {}, -LL + NonEmptyEnum2::Foo(_) | NonEmptyEnum2::Bar => todo!() +LL ~ _ if false => {}, +LL + NonEmptyEnum2::Foo(_) | NonEmptyEnum2::Bar => todo!() | error[E0004]: non-exhaustive patterns: `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered - --> $DIR/empty-match.rs:174:24 + --> $DIR/empty-match.rs:62:24 | LL | match_guarded_arm!(NonEmptyEnum5::V1); | ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered | note: `NonEmptyEnum5` defined here - --> $DIR/empty-match.rs:49:6 - | -LL | enum NonEmptyEnum5 { - | ^^^^^^^^^^^^^ -... -LL | V1, V2, V3, V4, V5, - | -- -- -- -- -- not covered - | | | | | - | | | | not covered - | | | not covered - | | not covered - | not covered + --> $DIR/empty-match.rs:38:10 + | +LL | enum NonEmptyEnum5 { + | ^^^^^^^^^^^^^ +LL | V1, + | -- not covered +LL | V2, + | -- not covered +LL | V3, + | -- not covered +LL | V4, + | -- not covered +LL | V5, + | -- not covered = note: the matched value is of type `NonEmptyEnum5` = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown, or multiple match arms | -LL ~ _ if false => {}, -LL + _ => todo!() +LL ~ _ if false => {}, +LL + _ => todo!() | -error: aborting due to 23 previous errors +error: aborting due to 16 previous errors -Some errors have detailed explanations: E0004, E0005. -For more information about an error, try `rustc --explain E0004`. +For more information about this error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-match.rs b/tests/ui/pattern/usefulness/empty-match.rs index fe5d0bce14fe3..321f24adc46b4 100644 --- a/tests/ui/pattern/usefulness/empty-match.rs +++ b/tests/ui/pattern/usefulness/empty-match.rs @@ -1,179 +1,65 @@ -// aux-build:empty.rs // revisions: normal exhaustive_patterns // // This tests a match with no arms on various types. #![feature(never_type)] -#![feature(never_type_fallback)] #![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))] #![deny(unreachable_patterns)] -//~^ NOTE the lint level is defined here -extern crate empty; - -enum EmptyEnum {} - -struct NonEmptyStruct1; -//~^ NOTE `NonEmptyStruct1` defined here -//~| NOTE `NonEmptyStruct1` defined here -struct NonEmptyStruct2(bool); -//~^ NOTE `NonEmptyStruct2` defined here -//~| NOTE `NonEmptyStruct2` defined here -union NonEmptyUnion1 { - //~^ NOTE `NonEmptyUnion1` defined here - //~| NOTE `NonEmptyUnion1` defined here - foo: (), -} -union NonEmptyUnion2 { - //~^ NOTE `NonEmptyUnion2` defined here - //~| NOTE `NonEmptyUnion2` defined here - foo: (), - bar: (), -} -enum NonEmptyEnum1 { - //~^ NOTE `NonEmptyEnum1` defined here - //~| NOTE `NonEmptyEnum1` defined here - Foo(bool), - //~^ NOTE not covered - //~| NOTE not covered -} -enum NonEmptyEnum2 { - //~^ NOTE `NonEmptyEnum2` defined here - //~| NOTE `NonEmptyEnum2` defined here - Foo(bool), - //~^ NOTE not covered - //~| NOTE not covered - Bar, - //~^ NOTE not covered - //~| NOTE not covered -} -enum NonEmptyEnum5 { - //~^ NOTE `NonEmptyEnum5` defined here - //~| NOTE `NonEmptyEnum5` defined here - V1, V2, V3, V4, V5, - //~^ NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered - //~| NOTE not covered -} - -fn empty_enum(x: EmptyEnum) { - match x {} // ok - match x { - _ => {}, //~ ERROR unreachable pattern +fn nonempty() { + macro_rules! match_no_arms { + ($e:expr) => { + match $e {} + }; } - match x { - _ if false => {}, //~ ERROR unreachable pattern + macro_rules! match_guarded_arm { + ($e:expr) => { + match $e { + _ if false => {} + } + }; } -} -fn empty_foreign_enum(x: empty::EmptyForeignEnum) { - match x {} // ok - match x { - _ => {}, //~ ERROR unreachable pattern + struct NonEmptyStruct1; + struct NonEmptyStruct2(bool); + union NonEmptyUnion1 { + foo: (), } - match x { - _ if false => {}, //~ ERROR unreachable pattern + union NonEmptyUnion2 { + foo: (), + bar: !, } -} - -fn empty_foreign_enum_private(x: Option) { - let None = x; - //~^ ERROR refutable pattern in local binding - //~| NOTE `let` bindings require an "irrefutable pattern" - //~| NOTE for more information, visit - //~| NOTE the matched value is of type - //~| NOTE pattern `Some(_)` not covered - //[exhaustive_patterns]~| NOTE currently uninhabited, but this variant contains private fields -} - -fn never(x: !) { - match x {} // ok - match x { - _ => {}, //~ ERROR unreachable pattern + enum NonEmptyEnum1 { + Foo(bool), } - match x { - _ if false => {}, //~ ERROR unreachable pattern + enum NonEmptyEnum2 { + Foo(bool), + Bar, + } + enum NonEmptyEnum5 { + V1, + V2, + V3, + V4, + V5, } -} - -macro_rules! match_no_arms { - ($e:expr) => { - match $e {} - }; -} -macro_rules! match_guarded_arm { - ($e:expr) => { - match $e { - _ if false => {} - } - }; -} -fn main() { match_no_arms!(0u8); //~ ERROR type `u8` is non-empty - //~| NOTE the matched value is of type match_no_arms!(NonEmptyStruct1); //~ ERROR type `NonEmptyStruct1` is non-empty - //~| NOTE the matched value is of type match_no_arms!(NonEmptyStruct2(true)); //~ ERROR type `NonEmptyStruct2` is non-empty - //~| NOTE the matched value is of type match_no_arms!((NonEmptyUnion1 { foo: () })); //~ ERROR type `NonEmptyUnion1` is non-empty - //~| NOTE the matched value is of type match_no_arms!((NonEmptyUnion2 { foo: () })); //~ ERROR type `NonEmptyUnion2` is non-empty - //~| NOTE the matched value is of type match_no_arms!(NonEmptyEnum1::Foo(true)); //~ ERROR `NonEmptyEnum1::Foo(_)` not covered - //~| NOTE pattern `NonEmptyEnum1::Foo(_)` not covered - //~| NOTE the matched value is of type match_no_arms!(NonEmptyEnum2::Foo(true)); //~ ERROR `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered - //~| NOTE patterns `NonEmptyEnum2::Foo(_)` and - //~| NOTE the matched value is of type match_no_arms!(NonEmptyEnum5::V1); //~ ERROR `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered - //~| NOTE patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2` - //~| NOTE the matched value is of type match_guarded_arm!(0u8); //~ ERROR `_` not covered - //~| NOTE the matched value is of type - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE pattern `_` not covered - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!(NonEmptyStruct1); //~ ERROR `NonEmptyStruct1` not covered - //~| NOTE pattern `NonEmptyStruct1` not covered - //~| NOTE the matched value is of type - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!(NonEmptyStruct2(true)); //~ ERROR `NonEmptyStruct2(_)` not covered - //~| NOTE the matched value is of type - //~| NOTE pattern `NonEmptyStruct2(_)` not covered - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!((NonEmptyUnion1 { foo: () })); //~ ERROR `NonEmptyUnion1 { .. }` not covered - //~| NOTE the matched value is of type - //~| NOTE pattern `NonEmptyUnion1 { .. }` not covered - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!((NonEmptyUnion2 { foo: () })); //~ ERROR `NonEmptyUnion2 { .. }` not covered - //~| NOTE the matched value is of type - //~| NOTE pattern `NonEmptyUnion2 { .. }` not covered - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!(NonEmptyEnum1::Foo(true)); //~ ERROR `NonEmptyEnum1::Foo(_)` not covered - //~| NOTE the matched value is of type - //~| NOTE pattern `NonEmptyEnum1::Foo(_)` not covered - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!(NonEmptyEnum2::Foo(true)); //~ ERROR `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered - //~| NOTE the matched value is of type - //~| NOTE patterns `NonEmptyEnum2::Foo(_)` and - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! match_guarded_arm!(NonEmptyEnum5::V1); //~ ERROR `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered - //~| NOTE the matched value is of type - //~| NOTE patterns `NonEmptyEnum5::V1`, - //~| NOTE match arms with guards don't count towards exhaustivity - //~| NOTE in this expansion of match_guarded_arm! } + +fn main() {} diff --git a/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr b/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr new file mode 100644 index 0000000000000..9a53b54704e9b --- /dev/null +++ b/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr @@ -0,0 +1,776 @@ +error: unreachable pattern + --> $DIR/empty-types.rs:47:9 + | +LL | _ => {} + | ^ + | +note: the lint level is defined here + --> $DIR/empty-types.rs:13:9 + | +LL | #![deny(unreachable_patterns)] + | ^^^^^^^^^^^^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:50:9 + | +LL | _x => {} + | ^^ + +error[E0004]: non-exhaustive patterns: type `&!` is non-empty + --> $DIR/empty-types.rs:54:11 + | +LL | match ref_never {} + | ^^^^^^^^^ + | + = note: the matched value is of type `&!` + = note: references are always considered inhabited +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match ref_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:62:9 + | +LL | &_ => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:69:9 + | +LL | (_, _) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:76:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:79:9 + | +LL | (_, _) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:83:9 + | +LL | _ => {} + | ^ + +error[E0004]: non-exhaustive patterns: `Ok(_)` not covered + --> $DIR/empty-types.rs:87:11 + | +LL | match res_u32_never {} + | ^^^^^^^^^^^^^ pattern `Ok(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ match res_u32_never { +LL + Ok(_) => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:95:9 + | +LL | Err(_) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:100:9 + | +LL | Err(_) => {} + | ^^^^^^ + +error[E0004]: non-exhaustive patterns: `Ok(1_u32..=u32::MAX)` not covered + --> $DIR/empty-types.rs:97:11 + | +LL | match res_u32_never { + | ^^^^^^^^^^^^^ pattern `Ok(1_u32..=u32::MAX)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ Err(_) => {}, +LL ~ Ok(1_u32..=u32::MAX) => todo!() + | + +error[E0005]: refutable pattern in local binding + --> $DIR/empty-types.rs:104:9 + | +LL | let Ok(_x) = res_u32_never.as_ref(); + | ^^^^^^ pattern `Err(_)` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: the matched value is of type `Result<&u32, &!>` +help: you might want to use `let else` to handle the variant that isn't matched + | +LL | let Ok(_x) = res_u32_never.as_ref() else { todo!() }; + | ++++++++++++++++ + +error: unreachable pattern + --> $DIR/empty-types.rs:115:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:119:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:122:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:123:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:126:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:127:9 + | +LL | Err(_) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:136:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:139:13 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:148:13 + | +LL | Some(_) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:152:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:158:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:167:13 + | +LL | Some(_) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:171:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:175:13 + | +LL | _a => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:180:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:185:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:204:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:209:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:214:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:219:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:225:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:234:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:239:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:245:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:251:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:256:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:262:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:268:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:284:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:287:9 + | +LL | (_, _) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:290:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:291:9 + | +LL | Err(_) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:296:9 + | +LL | &_ => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:299:9 + | +LL | Uninit { value: _ } => {} + | ^^^^^^^^^^^^^^^^^^^ + +error[E0004]: non-exhaustive patterns: type `&[!]` is non-empty + --> $DIR/empty-types.rs:323:11 + | +LL | match slice_never {} + | ^^^^^^^^^^^ + | + = note: the matched value is of type `&[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match slice_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:331:9 + | +LL | [_] => {} + | ^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:332:9 + | +LL | [_, _, ..] => {} + | ^^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:337:9 + | +LL | [_, _, _, ..] => {} + | ^^^^^^^^^^^^^ + +error[E0004]: non-exhaustive patterns: `&[]` not covered + --> $DIR/empty-types.rs:334:11 + | +LL | match slice_never { + | ^^^^^^^^^^^ pattern `&[]` not covered + | + = note: the matched value is of type `&[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL | [_, _, _, ..] => {}, &[] => todo!() + | ++++++++++++++++ + +error: unreachable pattern + --> $DIR/empty-types.rs:341:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:345:9 + | +LL | _x => {} + | ^^ + +error[E0004]: non-exhaustive patterns: `&[]` not covered + --> $DIR/empty-types.rs:347:11 + | +LL | match slice_never { + | ^^^^^^^^^^^ pattern `&[]` not covered + | + = note: the matched value is of type `&[!]` + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ &[..] if false => {}, +LL + &[] => todo!() + | + +error[E0004]: non-exhaustive patterns: type `[!]` is non-empty + --> $DIR/empty-types.rs:353:11 + | +LL | match *slice_never {} + | ^^^^^^^^^^^^ + | + = note: the matched value is of type `[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match *slice_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:363:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:366:9 + | +LL | [_, _, _] => {} + | ^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:369:9 + | +LL | [_, ..] => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:375:9 + | +LL | &[_, _, _] => {} + | ^^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:379:9 + | +LL | &[_x, _, _] => {} + | ^^^^^^^^^^^ + +error[E0004]: non-exhaustive patterns: type `[!; 0]` is non-empty + --> $DIR/empty-types.rs:383:11 + | +LL | match array_0_never {} + | ^^^^^^^^^^^^^ + | + = note: the matched value is of type `[!; 0]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match array_0_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:390:9 + | +LL | _ => {} + | ^ + +error[E0004]: non-exhaustive patterns: `[]` not covered + --> $DIR/empty-types.rs:392:11 + | +LL | match array_0_never { + | ^^^^^^^^^^^^^ pattern `[]` not covered + | + = note: the matched value is of type `[!; 0]` + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ [..] if false => {}, +LL + [] => todo!() + | + +error: unreachable pattern + --> $DIR/empty-types.rs:411:9 + | +LL | Some(_) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:416:9 + | +LL | Some(_a) => {} + | ^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:421:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:426:9 + | +LL | _a => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:436:9 + | +LL | &_ => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:444:9 + | +LL | &_a => {} + | ^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:453:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:458:9 + | +LL | _a => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:463:9 + | +LL | &_ => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:468:9 + | +LL | &_a => {} + | ^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:475:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:479:9 + | +LL | _a => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:485:9 + | +LL | ref _a => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:494:9 + | +LL | Some(_) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:499:9 + | +LL | Some(_a) => {} + | ^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:504:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:509:9 + | +LL | _a => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:514:14 + | +LL | _a @ Some(_) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:521:9 + | +LL | ref _a => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:526:18 + | +LL | ref _a @ Some(_) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:531:18 + | +LL | ref _a @ Some(_b) => {} + | ^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:538:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:542:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:544:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:549:9 + | +LL | Ok(_a) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:553:9 + | +LL | Ok(_a) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:555:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:559:9 + | +LL | Ok(_a) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:561:9 + | +LL | Err(_) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:569:9 + | +LL | (_, _) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:573:9 + | +LL | (_x, _) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:577:9 + | +LL | (_, _x) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:581:9 + | +LL | (0, _x) => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:583:9 + | +LL | (1.., _) => {} + | ^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:598:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:601:9 + | +LL | _x => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:604:9 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:607:9 + | +LL | _x if false => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:613:9 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:615:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:622:9 + | +LL | _a if false => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:624:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:629:9 + | +LL | _a if false => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:634:9 + | +LL | &_a if false => {} + | ^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:641:9 + | +LL | Ok(_x) if false => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:643:9 + | +LL | Ok(_) => {} + | ^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:645:9 + | +LL | Err(_) => {} + | ^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:650:9 + | +LL | (_, _x) if false => {} + | ^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:652:9 + | +LL | (_, _) => {} + | ^^^^^^ + +error: aborting due to 113 previous errors + +Some errors have detailed explanations: E0004, E0005. +For more information about an error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-types.normal.stderr b/tests/ui/pattern/usefulness/empty-types.normal.stderr new file mode 100644 index 0000000000000..b066393a61e60 --- /dev/null +++ b/tests/ui/pattern/usefulness/empty-types.normal.stderr @@ -0,0 +1,721 @@ +error: unreachable pattern + --> $DIR/empty-types.rs:47:9 + | +LL | _ => {} + | ^ + | +note: the lint level is defined here + --> $DIR/empty-types.rs:13:9 + | +LL | #![deny(unreachable_patterns)] + | ^^^^^^^^^^^^^^^^^^^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:50:9 + | +LL | _x => {} + | ^^ + +error[E0004]: non-exhaustive patterns: type `&!` is non-empty + --> $DIR/empty-types.rs:54:11 + | +LL | match ref_never {} + | ^^^^^^^^^ + | + = note: the matched value is of type `&!` + = note: references are always considered inhabited +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match ref_never { +LL + _ => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: type `(u32, !)` is non-empty + --> $DIR/empty-types.rs:66:11 + | +LL | match tuple_half_never {} + | ^^^^^^^^^^^^^^^^ + | + = note: the matched value is of type `(u32, !)` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match tuple_half_never { +LL + _ => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: type `(!, !)` is non-empty + --> $DIR/empty-types.rs:73:11 + | +LL | match tuple_never {} + | ^^^^^^^^^^^ + | + = note: the matched value is of type `(!, !)` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match tuple_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:83:9 + | +LL | _ => {} + | ^ + +error[E0004]: non-exhaustive patterns: `Ok(_)` and `Err(_)` not covered + --> $DIR/empty-types.rs:87:11 + | +LL | match res_u32_never {} + | ^^^^^^^^^^^^^ patterns `Ok(_)` and `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms + | +LL ~ match res_u32_never { +LL + Ok(_) | Err(_) => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: `Err(_)` not covered + --> $DIR/empty-types.rs:89:11 + | +LL | match res_u32_never { + | ^^^^^^^^^^^^^ pattern `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ Ok(_) => {}, +LL + Err(_) => todo!() + | + +error[E0004]: non-exhaustive patterns: `Ok(1_u32..=u32::MAX)` not covered + --> $DIR/empty-types.rs:97:11 + | +LL | match res_u32_never { + | ^^^^^^^^^^^^^ pattern `Ok(1_u32..=u32::MAX)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ Err(_) => {}, +LL ~ Ok(1_u32..=u32::MAX) => todo!() + | + +error[E0005]: refutable pattern in local binding + --> $DIR/empty-types.rs:102:9 + | +LL | let Ok(_x) = res_u32_never; + | ^^^^^^ pattern `Err(_)` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: the matched value is of type `Result` +help: you might want to use `let else` to handle the variant that isn't matched + | +LL | let Ok(_x) = res_u32_never else { todo!() }; + | ++++++++++++++++ + +error[E0005]: refutable pattern in local binding + --> $DIR/empty-types.rs:104:9 + | +LL | let Ok(_x) = res_u32_never.as_ref(); + | ^^^^^^ pattern `Err(_)` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: the matched value is of type `Result<&u32, &!>` +help: you might want to use `let else` to handle the variant that isn't matched + | +LL | let Ok(_x) = res_u32_never.as_ref() else { todo!() }; + | ++++++++++++++++ + +error[E0005]: refutable pattern in local binding + --> $DIR/empty-types.rs:108:9 + | +LL | let Ok(_x) = &res_u32_never; + | ^^^^^^ pattern `&Err(_)` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: the matched value is of type `&Result` +help: you might want to use `let else` to handle the variant that isn't matched + | +LL | let Ok(_x) = &res_u32_never else { todo!() }; + | ++++++++++++++++ + +error[E0004]: non-exhaustive patterns: `Ok(_)` and `Err(_)` not covered + --> $DIR/empty-types.rs:112:11 + | +LL | match result_never {} + | ^^^^^^^^^^^^ patterns `Ok(_)` and `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms + | +LL ~ match result_never { +LL + Ok(_) | Err(_) => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: `Err(_)` not covered + --> $DIR/empty-types.rs:117:11 + | +LL | match result_never { + | ^^^^^^^^^^^^ pattern `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL | Ok(_) => {}, Err(_) => todo!() + | +++++++++++++++++++ + +error: unreachable pattern + --> $DIR/empty-types.rs:136:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:139:13 + | +LL | _ if false => {} + | ^ + +error[E0004]: non-exhaustive patterns: `Some(_)` not covered + --> $DIR/empty-types.rs:142:15 + | +LL | match opt_void { + | ^^^^^^^^ pattern `Some(_)` not covered + | +note: `Option` defined here + --> $SRC_DIR/core/src/option.rs:LL:COL + ::: $SRC_DIR/core/src/option.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Option` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ None => {}, +LL + Some(_) => todo!() + | + +error: unreachable pattern + --> $DIR/empty-types.rs:158:13 + | +LL | _ => {} + | ^ + +error[E0004]: non-exhaustive patterns: `Some(_)` not covered + --> $DIR/empty-types.rs:161:15 + | +LL | match *ref_opt_void { + | ^^^^^^^^^^^^^ pattern `Some(_)` not covered + | +note: `Option` defined here + --> $SRC_DIR/core/src/option.rs:LL:COL + ::: $SRC_DIR/core/src/option.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Option` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ None => {}, +LL + Some(_) => todo!() + | + +error: unreachable pattern + --> $DIR/empty-types.rs:180:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:185:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:204:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:209:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:214:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:219:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:225:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:234:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:239:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:245:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:251:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:256:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:262:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:268:13 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:284:9 + | +LL | _ => {} + | ^ + +error[E0004]: non-exhaustive patterns: type `(u32, !)` is non-empty + --> $DIR/empty-types.rs:312:11 + | +LL | match *x {} + | ^^ + | + = note: the matched value is of type `(u32, !)` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match *x { +LL + _ => todo!(), +LL ~ } + | + +error[E0004]: non-exhaustive patterns: type `(!, !)` is non-empty + --> $DIR/empty-types.rs:314:11 + | +LL | match *x {} + | ^^ + | + = note: the matched value is of type `(!, !)` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match *x { +LL + _ => todo!(), +LL ~ } + | + +error[E0004]: non-exhaustive patterns: `Ok(_)` and `Err(_)` not covered + --> $DIR/empty-types.rs:316:11 + | +LL | match *x {} + | ^^ patterns `Ok(_)` and `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms + | +LL ~ match *x { +LL + Ok(_) | Err(_) => todo!(), +LL ~ } + | + +error[E0004]: non-exhaustive patterns: type `[!; 3]` is non-empty + --> $DIR/empty-types.rs:318:11 + | +LL | match *x {} + | ^^ + | + = note: the matched value is of type `[!; 3]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match *x { +LL + _ => todo!(), +LL ~ } + | + +error[E0004]: non-exhaustive patterns: type `&[!]` is non-empty + --> $DIR/empty-types.rs:323:11 + | +LL | match slice_never {} + | ^^^^^^^^^^^ + | + = note: the matched value is of type `&[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match slice_never { +LL + _ => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: `&[_, ..]` not covered + --> $DIR/empty-types.rs:325:11 + | +LL | match slice_never { + | ^^^^^^^^^^^ pattern `&[_, ..]` not covered + | + = note: the matched value is of type `&[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ [] => {}, +LL + &[_, ..] => todo!() + | + +error[E0004]: non-exhaustive patterns: `&[]`, `&[_]` and `&[_, _]` not covered + --> $DIR/empty-types.rs:334:11 + | +LL | match slice_never { + | ^^^^^^^^^^^ patterns `&[]`, `&[_]` and `&[_, _]` not covered + | + = note: the matched value is of type `&[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms + | +LL | [_, _, _, ..] => {}, &[] | &[_] | &[_, _] => todo!() + | +++++++++++++++++++++++++++++++++ + +error[E0004]: non-exhaustive patterns: `&[]` and `&[_, ..]` not covered + --> $DIR/empty-types.rs:347:11 + | +LL | match slice_never { + | ^^^^^^^^^^^ patterns `&[]` and `&[_, ..]` not covered + | + = note: the matched value is of type `&[!]` + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms + | +LL ~ &[..] if false => {}, +LL + &[] | &[_, ..] => todo!() + | + +error[E0004]: non-exhaustive patterns: type `[!]` is non-empty + --> $DIR/empty-types.rs:353:11 + | +LL | match *slice_never {} + | ^^^^^^^^^^^^ + | + = note: the matched value is of type `[!]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match *slice_never { +LL + _ => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: type `[!; 3]` is non-empty + --> $DIR/empty-types.rs:360:11 + | +LL | match array_3_never {} + | ^^^^^^^^^^^^^ + | + = note: the matched value is of type `[!; 3]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match array_3_never { +LL + _ => todo!(), +LL + } + | + +error[E0004]: non-exhaustive patterns: type `[!; 0]` is non-empty + --> $DIR/empty-types.rs:383:11 + | +LL | match array_0_never {} + | ^^^^^^^^^^^^^ + | + = note: the matched value is of type `[!; 0]` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match array_0_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:390:9 + | +LL | _ => {} + | ^ + +error[E0004]: non-exhaustive patterns: `[]` not covered + --> $DIR/empty-types.rs:392:11 + | +LL | match array_0_never { + | ^^^^^^^^^^^^^ pattern `[]` not covered + | + = note: the matched value is of type `[!; 0]` + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ [..] if false => {}, +LL + [] => todo!() + | + +error[E0004]: non-exhaustive patterns: `&Some(_)` not covered + --> $DIR/empty-types.rs:446:11 + | +LL | match ref_opt_never { + | ^^^^^^^^^^^^^ pattern `&Some(_)` not covered + | +note: `Option` defined here + --> $SRC_DIR/core/src/option.rs:LL:COL + ::: $SRC_DIR/core/src/option.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `&Option` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ &None => {}, +LL + &Some(_) => todo!() + | + +error: unreachable pattern + --> $DIR/empty-types.rs:475:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:479:9 + | +LL | _a => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:485:9 + | +LL | ref _a => {} + | ^^^^^^ + +error[E0004]: non-exhaustive patterns: `Some(_)` not covered + --> $DIR/empty-types.rs:487:11 + | +LL | match *ref_opt_never { + | ^^^^^^^^^^^^^^ pattern `Some(_)` not covered + | +note: `Option` defined here + --> $SRC_DIR/core/src/option.rs:LL:COL + ::: $SRC_DIR/core/src/option.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Option` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ None => {}, +LL + Some(_) => todo!() + | + +error[E0004]: non-exhaustive patterns: `Err(_)` not covered + --> $DIR/empty-types.rs:535:11 + | +LL | match *ref_res_never { + | ^^^^^^^^^^^^^^ pattern `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL | Ok(_) => {}, Err(_) => todo!() + | +++++++++++++++++++ + +error[E0004]: non-exhaustive patterns: `Err(_)` not covered + --> $DIR/empty-types.rs:546:11 + | +LL | match *ref_res_never { + | ^^^^^^^^^^^^^^ pattern `Err(_)` not covered + | +note: `Result` defined here + --> $SRC_DIR/core/src/result.rs:LL:COL + ::: $SRC_DIR/core/src/result.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Result` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL | Ok(_a) => {}, Err(_) => todo!() + | +++++++++++++++++++ + +error[E0004]: non-exhaustive patterns: type `(u32, !)` is non-empty + --> $DIR/empty-types.rs:565:11 + | +LL | match *ref_tuple_half_never {} + | ^^^^^^^^^^^^^^^^^^^^^ + | + = note: the matched value is of type `(u32, !)` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown + | +LL ~ match *ref_tuple_half_never { +LL + _ => todo!(), +LL + } + | + +error: unreachable pattern + --> $DIR/empty-types.rs:598:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:601:9 + | +LL | _x => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:604:9 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:607:9 + | +LL | _x if false => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:613:9 + | +LL | _ if false => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:615:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:622:9 + | +LL | _a if false => {} + | ^^ + +error: unreachable pattern + --> $DIR/empty-types.rs:624:9 + | +LL | _ => {} + | ^ + +error: unreachable pattern + --> $DIR/empty-types.rs:629:9 + | +LL | _a if false => {} + | ^^ + +error[E0004]: non-exhaustive patterns: `&_` not covered + --> $DIR/empty-types.rs:631:11 + | +LL | match ref_never { + | ^^^^^^^^^ pattern `&_` not covered + | + = note: the matched value is of type `&!` + = note: references are always considered inhabited + = note: match arms with guards don't count towards exhaustivity +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL | &_a if false => {}, &_ => todo!() + | +++++++++++++++ + +error[E0004]: non-exhaustive patterns: `Some(_)` not covered + --> $DIR/empty-types.rs:659:11 + | +LL | match *x { + | ^^ pattern `Some(_)` not covered + | +note: `Option>` defined here + --> $SRC_DIR/core/src/option.rs:LL:COL + ::: $SRC_DIR/core/src/option.rs:LL:COL + | + = note: not covered + = note: the matched value is of type `Option>` +help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown + | +LL ~ None => {}, +LL + Some(_) => todo!() + | + +error: aborting due to 66 previous errors + +Some errors have detailed explanations: E0004, E0005. +For more information about an error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-types.rs b/tests/ui/pattern/usefulness/empty-types.rs new file mode 100644 index 0000000000000..fc422298a3192 --- /dev/null +++ b/tests/ui/pattern/usefulness/empty-types.rs @@ -0,0 +1,665 @@ +// revisions: normal exhaustive_patterns +// +// This tests correct handling of empty types in exhaustiveness checking. +// +// Most of the subtlety of this file happens in scrutinee places which are not required to hold +// valid data, namely dereferences and union field accesses. In these cases, empty arms can +// generally not be omitted, except with `exhaustive_patterns` which ignores this.. +#![feature(never_type)] +// This feature is useful to avoid `!` falling back to `()` all the time. +#![feature(never_type_fallback)] +#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))] +#![allow(dead_code, unreachable_code)] +#![deny(unreachable_patterns)] + +#[derive(Copy, Clone)] +enum Void {} + +/// A bunch of never situations that can't be normally constructed. +#[derive(Copy, Clone)] +struct NeverBundle { + never: !, + void: Void, + tuple_never: (!, !), + tuple_half_never: (u32, !), + array_3_never: [!; 3], + result_never: Result, +} + +/// A simplified `MaybeUninit` to test union field accesses. +#[derive(Copy, Clone)] +union Uninit { + value: T, + uninit: (), +} + +impl Uninit { + fn new() -> Self { + Self { uninit: () } + } +} + +// Simple cases of omitting empty arms, all with known_valid scrutinees. +fn basic(x: NeverBundle) { + let never: ! = x.never; + match never {} + match never { + _ => {} //~ ERROR unreachable pattern + } + match never { + _x => {} //~ ERROR unreachable pattern + } + + let ref_never: &! = &x.never; + match ref_never {} + //~^ ERROR non-empty + match ref_never { + // useful, reachable + _ => {} + } + match ref_never { + // useful, reachable + &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let tuple_half_never: (u32, !) = x.tuple_half_never; + match tuple_half_never {} + //[normal]~^ ERROR non-empty + match tuple_half_never { + (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let tuple_never: (!, !) = x.tuple_never; + match tuple_never {} + //[normal]~^ ERROR non-empty + match tuple_never { + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match tuple_never { + (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match tuple_never.0 {} + match tuple_never.0 { + _ => {} //~ ERROR unreachable pattern + } + + let res_u32_never: Result = Ok(0); + match res_u32_never {} + //~^ ERROR non-exhaustive + match res_u32_never { + //[normal]~^ ERROR non-exhaustive + Ok(_) => {} + } + match res_u32_never { + Ok(_) => {} + Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match res_u32_never { + //~^ ERROR non-exhaustive + Ok(0) => {} + Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + let Ok(_x) = res_u32_never; + //[normal]~^ ERROR refutable + let Ok(_x) = res_u32_never.as_ref(); + //~^ ERROR refutable + // Non-obvious difference: here there's an implicit dereference in the patterns, which makes the + // inner place !known_valid. `exhaustive_patterns` ignores this. + let Ok(_x) = &res_u32_never; + //[normal]~^ ERROR refutable + + let result_never: Result = x.result_never; + match result_never {} + //[normal]~^ ERROR non-exhaustive + match result_never { + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match result_never { + //[normal]~^ ERROR non-exhaustive + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match result_never { + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match result_never { + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } +} + +// Check for a few cases that `Void` and `!` are treated the same. +fn void_same_as_never(x: NeverBundle) { + unsafe { + match x.void {} + match x.void { + _ => {} //~ ERROR unreachable pattern + } + match x.void { + _ if false => {} //~ ERROR unreachable pattern + } + let opt_void: Option = None; + match opt_void { + //[normal]~^ ERROR non-exhaustive + None => {} + } + match opt_void { + None => {} + Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match opt_void { + None => {} + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let ref_void: &Void = &x.void; + match *ref_void {} + match *ref_void { + _ => {} //~ ERROR unreachable pattern + } + let ref_opt_void: &Option = &None; + match *ref_opt_void { + //[normal]~^ ERROR non-exhaustive + None => {} + } + match *ref_opt_void { + None => {} + Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_void { + None => {} + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_void { + None => {} + _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + let union_void = Uninit::::new(); + match union_void.value {} + match union_void.value { + _ => {} //~ ERROR unreachable pattern + } + let ptr_void: *const Void = std::ptr::null(); + match *ptr_void {} + match *ptr_void { + _ => {} //~ ERROR unreachable pattern + } + } +} + +// Test if we correctly determine validity from the scrutinee expression. +fn invalid_scrutinees(x: NeverBundle) { + let ptr_never: *const ! = std::ptr::null(); + let never: ! = x.never; + let ref_never: &! = &never; + + struct NestedNeverBundle(NeverBundle); + let nested_x = NestedNeverBundle(x); + + // These should be considered known_valid and warn unreachable. + unsafe { + // A plain `!` value must be valid. + match never {} + match never { + _ => {} //~ ERROR unreachable pattern + } + // A block forces a copy. + match { *ptr_never } {} + match { *ptr_never } { + _ => {} //~ ERROR unreachable pattern + } + // This field access is not a dereference. + match x.never {} + match x.never { + _ => {} //~ ERROR unreachable pattern + } + // This nested field access is not a dereference. + match nested_x.0.never {} + match nested_x.0.never { + _ => {} //~ ERROR unreachable pattern + } + // Indexing is like a field access. This one does not access behind a reference. + let array_3_never: [!; 3] = x.array_3_never; + match array_3_never[0] {} + match array_3_never[0] { + _ => {} //~ ERROR unreachable pattern + } + } + + // These should be considered !known_valid and not warn unreachable. + unsafe { + // A pointer may point to a place with an invalid value. + match *ptr_never {} + match *ptr_never { + _ => {} //~ ERROR unreachable pattern + } + // A reference may point to a place with an invalid value. + match *ref_never {} + match *ref_never { + _ => {} //~ ERROR unreachable pattern + } + // This field access is a dereference. + let ref_x: &NeverBundle = &x; + match ref_x.never {} + match ref_x.never { + _ => {} //~ ERROR unreachable pattern + } + // This nested field access is a dereference. + let nested_ref_x: &NestedNeverBundle = &nested_x; + match nested_ref_x.0.never {} + match nested_ref_x.0.never { + _ => {} //~ ERROR unreachable pattern + } + // A cast does not load. + match (*ptr_never as Void) {} + match (*ptr_never as Void) { + _ => {} //~ ERROR unreachable pattern + } + // A union field may contain invalid data. + let union_never = Uninit::::new(); + match union_never.value {} + match union_never.value { + _ => {} //~ ERROR unreachable pattern + } + // Indexing is like a field access. This one accesses behind a reference. + let slice_never: &[!] = &[]; + match slice_never[0] {} + match slice_never[0] { + _ => {} //~ ERROR unreachable pattern + } + } +} + +// Test we correctly track validity as we dig into patterns. Validity changes when we go under a +// dereference or a union field access, and it otherwise preserved. +fn nested_validity_tracking(bundle: NeverBundle) { + let never: ! = bundle.never; + let ref_never: &! = &never; + let tuple_never: (!, !) = bundle.tuple_never; + let result_never: Result = bundle.result_never; + let union_never = Uninit::::new(); + + // These should be considered known_valid and warn unreachable. + match never { + _ => {} //~ ERROR unreachable pattern + } + match tuple_never { + (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match result_never { + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + // These should be considered !known_valid and not warn unreachable. + match ref_never { + &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match union_never { + Uninit { value: _ } => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } +} + +// Test we don't allow empty matches on empty types if the scrutinee is `!known_valid`. +fn invalid_empty_match(bundle: NeverBundle) { + // We allow these two for backwards-compability. + let x: &! = &bundle.never; + match *x {} + let x: &Void = &bundle.void; + match *x {} + + let x: &(u32, !) = &bundle.tuple_half_never; + match *x {} //[normal]~ ERROR non-exhaustive + let x: &(!, !) = &bundle.tuple_never; + match *x {} //[normal]~ ERROR non-exhaustive + let x: &Result = &bundle.result_never; + match *x {} //[normal]~ ERROR non-exhaustive + let x: &[!; 3] = &bundle.array_3_never; + match *x {} //[normal]~ ERROR non-exhaustive +} + +fn arrays_and_slices(x: NeverBundle) { + let slice_never: &[!] = &[]; + match slice_never {} + //~^ ERROR non-empty + match slice_never { + //[normal]~^ ERROR not covered + [] => {} + } + match slice_never { + [] => {} + [_] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + [_, _, ..] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match slice_never { + //[normal]~^ ERROR `&[]`, `&[_]` and `&[_, _]` not covered + //[exhaustive_patterns]~^^ ERROR `&[]` not covered + [_, _, _, ..] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match slice_never { + [] => {} + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match slice_never { + [] => {} + _x => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match slice_never { + //[normal]~^ ERROR `&[]` and `&[_, ..]` not covered + //[exhaustive_patterns]~^^ ERROR `&[]` not covered + &[..] if false => {} + } + + match *slice_never {} + //~^ ERROR non-empty + match *slice_never { + _ => {} + } + + let array_3_never: [!; 3] = x.array_3_never; + match array_3_never {} + //[normal]~^ ERROR non-empty + match array_3_never { + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match array_3_never { + [_, _, _] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match array_3_never { + [_, ..] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let ref_array_3_never: &[!; 3] = &array_3_never; + match ref_array_3_never { + // useful, reachable + &[_, _, _] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match ref_array_3_never { + // useful, !reachable + &[_x, _, _] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let array_0_never: [!; 0] = []; + match array_0_never {} + //~^ ERROR non-empty + match array_0_never { + [] => {} + } + match array_0_never { + [] => {} + _ => {} //~ ERROR unreachable pattern + } + match array_0_never { + //~^ ERROR `[]` not covered + [..] if false => {} + } +} + +// The difference between `_` and `_a` patterns is that `_a` loads the value. In case of an empty +// type, this asserts validity of the value, and thus the binding is unreachable. We don't yet +// distinguish these cases since we don't lint "unreachable" on `useful && !reachable` arms. +// Once/if never patterns are a thing, we can warn that the `_a` cases should be never patterns. +fn bindings(x: NeverBundle) { + let opt_never: Option = None; + let ref_never: &! = &x.never; + let ref_opt_never: &Option = &None; + + // On a known_valid place. + match opt_never { + None => {} + // !useful, !reachable + Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match opt_never { + None => {} + // !useful, !reachable + Some(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match opt_never { + None => {} + // !useful, !reachable + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match opt_never { + None => {} + // !useful, !reachable + _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + // The scrutinee is known_valid, but under the `&` isn't anymore. + match ref_never { + // useful, reachable + _ => {} + } + match ref_never { + // useful, reachable + &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match ref_never { + // useful, reachable + _a => {} + } + match ref_never { + // useful, !reachable + &_a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match ref_opt_never { + //[normal]~^ ERROR non-exhaustive + &None => {} + } + match ref_opt_never { + &None => {} + // useful, reachable + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match ref_opt_never { + &None => {} + // useful, reachable + _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match ref_opt_never { + &None => {} + // useful, reachable + &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match ref_opt_never { + &None => {} + // useful, !reachable + &_a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + // On a !known_valid place. + match *ref_never {} + match *ref_never { + // useful, reachable + _ => {} //~ ERROR unreachable pattern + } + match *ref_never { + // useful, !reachable + _a => {} //~ ERROR unreachable pattern + } + // This is equivalent to `match ref_never { _a => {} }`. In other words, it asserts validity of + // `ref_never` but says nothing of the data at `*ref_never`. + match *ref_never { + // useful, reachable + ref _a => {} //~ ERROR unreachable pattern + } + match *ref_opt_never { + //[normal]~^ ERROR non-exhaustive + None => {} + } + match *ref_opt_never { + None => {} + // useful, reachable + Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_never { + None => {} + // useful, !reachable + Some(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_never { + None => {} + // useful, reachable + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_never { + None => {} + // useful, !reachable + _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_never { + None => {} + // useful, !reachable + _a @ Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + // This is equivalent to `match ref_opt_never { None => {}, _a => {} }`. In other words, it + // asserts validity of `ref_opt_never` but says nothing of the data at `*ref_opt_never`. + match *ref_opt_never { + None => {} + // useful, reachable + ref _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_never { + None => {} + // useful, reachable + ref _a @ Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_opt_never { + None => {} + // useful, !reachable + ref _a @ Some(_b) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let ref_res_never: &Result = &x.result_never; + match *ref_res_never { + //[normal]~^ ERROR non-exhaustive + // useful, reachable + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_res_never { + // useful, reachable + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // useful, reachable + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_res_never { + //[normal]~^ ERROR non-exhaustive + // useful, !reachable + Ok(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_res_never { + // useful, !reachable + Ok(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // useful, reachable + _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_res_never { + // useful, !reachable + Ok(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // useful, reachable + Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + let ref_tuple_half_never: &(u32, !) = &x.tuple_half_never; + match *ref_tuple_half_never {} + //[normal]~^ ERROR non-empty + match *ref_tuple_half_never { + // useful, reachable + (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_tuple_half_never { + // useful, reachable + (_x, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_tuple_half_never { + // useful, !reachable + (_, _x) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + match *ref_tuple_half_never { + // useful, !reachable + (0, _x) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // useful, reachable + (1.., _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } +} + +// When we execute the condition for a guard we loads from all bindings. This asserts validity at +// all places with bindings. Surprisingly this can make subsequent arms unreachable. We choose to +// not detect this in exhaustiveness because this is rather subtle. With never patterns, we would +// recommend using a never pattern instead. +fn guards_and_validity(x: NeverBundle) { + let never: ! = x.never; + let ref_never: &! = &never; + + // Basic guard behavior when known_valid. + match never {} + match never { + _ => {} //~ ERROR unreachable pattern + } + match never { + _x => {} //~ ERROR unreachable pattern + } + match never { + _ if false => {} //~ ERROR unreachable pattern + } + match never { + _x if false => {} //~ ERROR unreachable pattern + } + + // If the pattern under the guard doesn't load, all is normal. + match *ref_never { + // useful, reachable + _ if false => {} //~ ERROR unreachable pattern + // useful, reachable + _ => {} //~ ERROR unreachable pattern + } + // Now the madness commences. The guard caused a load of the value thus asserting validity. So + // there's no invalid value for `_` to catch. So the second pattern is unreachable despite the + // guard not being taken. + match *ref_never { + // useful, !reachable + _a if false => {} //~ ERROR unreachable pattern + // !useful, !reachable + _ => {} //~ ERROR unreachable pattern + } + // The above still applies to the implicit `_` pattern used for exhaustiveness. + match *ref_never { + // useful, !reachable + _a if false => {} //~ ERROR unreachable pattern + } + match ref_never { + //[normal]~^ ERROR non-exhaustive + // useful, !reachable + &_a if false => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + + // Same but with subpatterns. + let ref_result_never: &Result = &x.result_never; + match *ref_result_never { + // useful, !reachable + Ok(_x) if false => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // !useful, !reachable + Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // useful, !reachable + Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } + let ref_tuple_never: &(!, !) = &x.tuple_never; + match *ref_tuple_never { + // useful, !reachable + (_, _x) if false => {} //[exhaustive_patterns]~ ERROR unreachable pattern + // !useful, !reachable + (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + } +} + +fn diagnostics_subtlety(x: NeverBundle) { + // Regression test for diagnostics: don't report `Some(Ok(_))` and `Some(Err(_))`. + let x: &Option> = &None; + match *x { + //[normal]~^ ERROR `Some(_)` not covered + None => {} + } +} + +fn main() {} diff --git a/tests/ui/uninhabited/uninhabited-patterns.rs b/tests/ui/uninhabited/uninhabited-patterns.rs index f1573b6adf0ce..43b19e790e2f8 100644 --- a/tests/ui/uninhabited/uninhabited-patterns.rs +++ b/tests/ui/uninhabited/uninhabited-patterns.rs @@ -1,8 +1,6 @@ #![feature(box_patterns)] #![feature(never_type)] #![feature(exhaustive_patterns)] - - #![deny(unreachable_patterns)] mod foo { @@ -23,22 +21,22 @@ fn main() { let x: &[!] = &[]; match x { - &[] => (), - &[..] => (), //~ ERROR unreachable pattern + &[] => (), + &[..] => (), //~ ERROR unreachable pattern }; let x: Result, &[Result]> = Err(&[]); match x { - Ok(box _) => (), //~ ERROR unreachable pattern + Ok(box _) => (), //~ ERROR unreachable pattern Err(&[]) => (), - Err(&[..]) => (), //~ ERROR unreachable pattern + Err(&[..]) => (), //~ ERROR unreachable pattern } let x: Result> = Err(Err(123)); match x { Ok(_y) => (), Err(Err(_y)) => (), - Err(Ok(_y)) => (), //~ ERROR unreachable pattern + Err(Ok(_y)) => (), //~ ERROR unreachable pattern } while let Some(_y) = foo() { diff --git a/tests/ui/uninhabited/uninhabited-patterns.stderr b/tests/ui/uninhabited/uninhabited-patterns.stderr index 655569ad6e086..19f34a52bdbe5 100644 --- a/tests/ui/uninhabited/uninhabited-patterns.stderr +++ b/tests/ui/uninhabited/uninhabited-patterns.stderr @@ -1,35 +1,35 @@ error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:27:9 + --> $DIR/uninhabited-patterns.rs:25:9 | LL | &[..] => (), | ^^^^^ | note: the lint level is defined here - --> $DIR/uninhabited-patterns.rs:6:9 + --> $DIR/uninhabited-patterns.rs:4:9 | LL | #![deny(unreachable_patterns)] | ^^^^^^^^^^^^^^^^^^^^ error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:32:9 + --> $DIR/uninhabited-patterns.rs:30:9 | LL | Ok(box _) => (), | ^^^^^^^^^ error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:34:9 + --> $DIR/uninhabited-patterns.rs:32:9 | LL | Err(&[..]) => (), | ^^^^^^^^^^ error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:41:9 + --> $DIR/uninhabited-patterns.rs:39:9 | LL | Err(Ok(_y)) => (), | ^^^^^^^^^^^ error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:44:15 + --> $DIR/uninhabited-patterns.rs:42:15 | LL | while let Some(_y) = foo() { | ^^^^^^^^ From 9aafc0b815a86924996c31943f6e2de0a0a6f973 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sat, 18 Nov 2023 04:17:50 +0100 Subject: [PATCH 2/7] Be precise about usefulness vs reachability --- .../src/thir/pattern/check_match.rs | 18 +- .../src/thir/pattern/deconstruct_pat.rs | 37 ++-- .../src/thir/pattern/usefulness.rs | 198 ++++++++++++------ 3 files changed, 159 insertions(+), 94 deletions(-) diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs index b72b9da21b7d1..89b7b3619bebd 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs @@ -1,6 +1,6 @@ use super::deconstruct_pat::{Constructor, DeconstructedPat, WitnessPat}; use super::usefulness::{ - compute_match_usefulness, MatchArm, MatchCheckCtxt, Reachability, UsefulnessReport, + compute_match_usefulness, MatchArm, MatchCheckCtxt, Usefulness, UsefulnessReport, }; use crate::errors::*; @@ -749,18 +749,18 @@ fn report_arm_reachability<'p, 'tcx>( ); }; - use Reachability::*; + use Usefulness::*; let mut catchall = None; for (arm, is_useful) in report.arm_usefulness.iter() { match is_useful { - Unreachable => report_unreachable_pattern(arm.pat.span(), arm.hir_id, catchall), - Reachable(unreachables) if unreachables.is_empty() => {} - // The arm is reachable, but contains unreachable subpatterns (from or-patterns). - Reachable(unreachables) => { - let mut unreachables = unreachables.clone(); + Redundant => report_unreachable_pattern(arm.pat.span(), arm.hir_id, catchall), + Useful(redundant_spans) if redundant_spans.is_empty() => {} + // The arm is reachable, but contains redundant subpatterns (from or-patterns). + Useful(redundant_spans) => { + let mut redundant_spans = redundant_spans.clone(); // Emit lints in the order in which they occur in the file. - unreachables.sort_unstable(); - for span in unreachables { + redundant_spans.sort_unstable(); + for span in redundant_spans { report_unreachable_pattern(span, arm.hir_id, None); } } diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs index ddcceeb7ef6b1..094acbc3f8aa0 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs @@ -1339,7 +1339,8 @@ pub(crate) struct DeconstructedPat<'p, 'tcx> { fields: Fields<'p, 'tcx>, ty: Ty<'tcx>, span: Span, - reachable: Cell, + /// Whether removing this arm would change the behavior of the match expression. + useful: Cell, } impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { @@ -1353,7 +1354,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { ty: Ty<'tcx>, span: Span, ) -> Self { - DeconstructedPat { ctor, fields, ty, span, reachable: Cell::new(false) } + DeconstructedPat { ctor, fields, ty, span, useful: Cell::new(false) } } /// Note: the input patterns must have been lowered through @@ -1634,38 +1635,38 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { } } - /// We keep track for each pattern if it was ever reachable during the analysis. This is used - /// with `unreachable_spans` to report unreachable subpatterns arising from or patterns. - pub(super) fn set_reachable(&self) { - self.reachable.set(true) + /// We keep track for each pattern if it was ever useful during the analysis. This is used + /// with `redundant_spans` to report redundant subpatterns arising from or patterns. + pub(super) fn set_useful(&self) { + self.useful.set(true) } - pub(super) fn is_reachable(&self) -> bool { - if self.reachable.get() { + pub(super) fn is_useful(&self) -> bool { + if self.useful.get() { true - } else if self.is_or_pat() && self.iter_fields().any(|f| f.is_reachable()) { + } else if self.is_or_pat() && self.iter_fields().any(|f| f.is_useful()) { // We always expand or patterns in the matrix, so we will never see the actual // or-pattern (the one with constructor `Or`) in the column. As such, it will not be - // marked as reachable itself, only its children will. We recover this information here. - self.set_reachable(); + // marked as useful itself, only its children will. We recover this information here. + self.set_useful(); true } else { false } } - /// Report the spans of subpatterns that were not reachable, if any. - pub(super) fn unreachable_spans(&self) -> Vec { + /// Report the spans of subpatterns that were not useful, if any. + pub(super) fn redundant_spans(&self) -> Vec { let mut spans = Vec::new(); - self.collect_unreachable_spans(&mut spans); + self.collect_redundant_spans(&mut spans); spans } - fn collect_unreachable_spans(&self, spans: &mut Vec) { - // We don't look at subpatterns if we already reported the whole pattern as unreachable. - if !self.is_reachable() { + fn collect_redundant_spans(&self, spans: &mut Vec) { + // We don't look at subpatterns if we already reported the whole pattern as redundant. + if !self.is_useful() { spans.push(self.span); } else { for p in self.iter_fields() { - p.collect_unreachable_spans(spans); + p.collect_redundant_spans(spans); } } } diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs index a2f829f93e3a9..e77f158a980ab 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs @@ -1,8 +1,8 @@ -//! # Match exhaustiveness and reachability algorithm +//! # Match exhaustiveness and redundancy algorithm //! -//! This file contains the logic for exhaustiveness and reachability checking for pattern-matching. +//! This file contains the logic for exhaustiveness and usefulness checking for pattern-matching. //! Specifically, given a list of patterns in a match, we can tell whether: -//! (a) a given pattern is reachable (reachability) +//! (a) a given pattern is redundant //! (b) the patterns cover every possible value for the type (exhaustiveness) //! //! The algorithm implemented here is inspired from the one described in [this @@ -19,15 +19,15 @@ //! The algorithm is given as input a list of patterns, one for each arm of a match, and computes //! the following: //! - a set of values that match none of the patterns (if any), -//! - for each subpattern (taking into account or-patterns), whether it would catch any value that -//! isn't caught by a pattern before it, i.e. whether it is reachable. +//! - for each subpattern (taking into account or-patterns), whether removing it would change +//! anything about how the match executes, i.e. whether it is useful/not redundant. //! //! To a first approximation, the algorithm works by exploring all possible values for the type //! being matched on, and determining which arm(s) catch which value. To make this tractable we //! cleverly group together values, as we'll see below. //! //! The entrypoint of this file is the [`compute_match_usefulness`] function, which computes -//! reachability for each subpattern and exhaustiveness for the whole match. +//! usefulness for each subpattern and exhaustiveness for the whole match. //! //! In this page we explain the necessary concepts to understand how the algorithm works. //! @@ -39,17 +39,17 @@ //! none of the `p_i`. We write `usefulness(p_1 .. p_n, q)` for a function that returns a list of //! such values. The aim of this file is to compute it efficiently. //! -//! This is enough to compute reachability: a pattern in a `match` expression is reachable iff it is -//! useful w.r.t. the patterns above it: +//! This is enough to compute usefulness: a pattern in a `match` expression is redundant iff it is +//! not useful w.r.t. the patterns above it: //! ```compile_fail,E0004 //! # #![feature(exclusive_range_pattern)] //! # fn foo() { //! match Some(0u32) { //! Some(0..100) => {}, -//! Some(90..190) => {}, // reachable: `Some(150)` is matched by this but not the branch above -//! Some(50..150) => {}, // unreachable: all the values this matches are already matched by +//! Some(90..190) => {}, // useful: `Some(150)` is matched by this but not the branch above +//! Some(50..150) => {}, // redundant: all the values this matches are already matched by //! // the branches above -//! None => {}, // reachable: `None` is matched by this but not the branches above +//! None => {}, // useful: `None` is matched by this but not the branches above //! } //! # } //! ``` @@ -246,18 +246,17 @@ //! //! //! -//! # Computing reachability and exhaustiveness in one go +//! # Computing usefulness and exhaustiveness in one go //! -//! The algorithm we have described so far computes usefulness of each pattern in turn to check if -//! it is reachable, and ends by checking if `_` is useful to determine exhaustiveness of the whole -//! match. In practice, instead of doing "for each pattern { for each constructor { ... } }", we do -//! "for each constructor { for each pattern { ... } }". This allows us to compute everything in one -//! go. +//! The algorithm we have described so far computes usefulness of each pattern in turn, and ends by +//! checking if `_` is useful to determine exhaustiveness of the whole match. In practice, instead +//! of doing "for each pattern { for each constructor { ... } }", we do "for each constructor { for +//! each pattern { ... } }". This allows us to compute everything in one go. //! -//! [`Matrix`] stores the set of pattern-tuples under consideration. We track reachability of each +//! [`Matrix`] stores the set of pattern-tuples under consideration. We track usefulness of each //! row mutably in the matrix as we go along. We ignore witnesses of usefulness of the match rows. //! We gather witnesses of the usefulness of `_` in [`WitnessMatrix`]. The algorithm that computes -//! all this is in [`compute_exhaustiveness_and_reachability`]. +//! all this is in [`compute_exhaustiveness_and_usefulness`]. //! //! See the full example at the bottom of this documentation. //! @@ -279,7 +278,7 @@ //! ``` //! //! In this example, trying any of `0`, `1`, .., `49` will give the same specialized matrix, and -//! thus the same reachability/exhaustiveness results. We can thus accelerate the algorithm by +//! thus the same usefulness/exhaustiveness results. We can thus accelerate the algorithm by //! trying them all at once. Here in fact, the only cases we need to consider are: `0..50`, //! `50..=100`, `101..=150`,`151..=200` and `201..`. //! @@ -299,15 +298,16 @@ //! This is done in [`ConstructorSet::split`] and explained in [`super::deconstruct_pat`]. //! //! +//! //! # Or-patterns //! //! What we have described so far works well if there are no or-patterns. To handle them, if the //! first pattern of a row in the matrix is an or-pattern, we expand it by duplicating the rest of //! the row as necessary. This is handled automatically in [`Matrix`]. //! -//! This makes reachability tracking subtle, because we also want to compute whether an alternative -//! of an or-pattern is unreachable, e.g. in `Some(_) | Some(0)`. We track reachability of each -//! subpattern by interior mutability in [`DeconstructedPat`] with `set_reachable`/`is_reachable`. +//! This makes usefulness tracking subtle, because we also want to compute whether an alternative +//! of an or-pattern is redundant, e.g. in `Some(_) | Some(0)`. We track usefulness of each +//! subpattern by interior mutability in [`DeconstructedPat`] with `set_useful`/`is_useful`. //! //! It's unfortunate that we have to use interior mutability, but believe me (Nadrieril), I have //! tried [other](https://github.com/rust-lang/rust/pull/80104) @@ -332,6 +332,69 @@ //! //! //! +//! # Usefulness vs reachability, validity, and empty patterns +//! +//! This is likely the subtlest aspect of the algorithm. To be fully precise, a match doesn't +//! operate on a value, it operates on a place. In certain unsafe circumstances, it is possible for +//! a place to not contain valid data for its type. This has subtle consequences for empty types. +//! Take the following: +//! +//! ```rust +//! enum Void {} +//! let x: u8 = 0; +//! let ptr: *const Void = &x as *const u8 as *const Void; +//! unsafe { +//! match *ptr { +//! _ => println!("Reachable!"), +//! } +//! } +//! ``` +//! +//! In this example, `ptr` is a valid pointer pointing to a place with invalid data. The `_` pattern +//! does not look at the contents of `*ptr`, so this is ok and the arm is taken. In other words, +//! despite the place we are inspecting being of type `Void`, there is a reachable arm. If the +//! arm had a binding however: +//! +//! ```rust +//! # #[derive(Copy, Clone)] +//! # enum Void {} +//! # let x: u8 = 0; +//! # let ptr: *const Void = &x as *const u8 as *const Void; +//! # unsafe { +//! match *ptr { +//! _a => println!("Unreachable!"), +//! } +//! # } +//! ``` +//! +//! Here the binding loads the value of type `Void` from the `*ptr` place. In this example, this +//! causes UB since the data is not valid. In the general case, this asserts validity of the data at +//! `*ptr`. Either way, this arm will never be taken. +//! +//! Finally, let's consider the empty match `match *ptr {}`. If we consider this exhaustive, then +//! having invalid data at `*ptr` is invalid. In other words, the empty match is semantically +//! equivalent to the `_a => ...` match. In the interest of explicitness, we prefer the case with an +//! arm, hence we won't tell the user to remove the `_a` arm. In other words, the `_a` arm is +//! unreachable yet not redundant. This is why we lint on redundant arms rather than unreachable +//! arms, despite the fact that the lint says "unreachable". +//! +//! These considerations only affects certain places, namely those that can contain non-valid data +//! without UB. These are: pointer dereferences, reference dereferences, and union field accesses. +//! We track in the algorithm whether a given place is known to contain valid data. This is done +//! first by inspecting the scrutinee syntactically (which gives us `cx.known_valid_scrutinee`), and +//! then by tracking validity of each column of the matrix (which correspond to places) as we +//! recurse into subpatterns. That second part is done through [`ValidityConstraint`], most notably +//! [`ValidityConstraint::specialize`]. +//! +//! Having said all that, in practice we don't fully follow what's been presented in this section. +//! Under `exhaustive_patterns`, we allow omitting empty arms even in `!known_valid` places, for +//! backwards-compatibility until we have a better alternative. Without `exhaustive_patterns`, we +//! mostly treat empty types as inhabited, except specifically a non-nested `!` or empty enum. In +//! this specific case we also allow the empty match regardless of place validity, for +//! backwards-compatibility. Hopefully we can eventually deprecate this. +//! +//! +//! //! # Full example //! //! We illustrate a full run of the algorithm on the following match. @@ -348,7 +411,7 @@ //! ``` //! //! We keep track of the original row for illustration purposes, this is not what the algorithm -//! actually does (it tracks reachability as a boolean on each row). +//! actually does (it tracks usefulness as a boolean on each row). //! //! ```text //! ┐ Patterns: @@ -377,7 +440,7 @@ //! │ │ │ ├─┐ Patterns: //! │ │ │ │ │ 1. `[]` //! │ │ │ │ │ -//! │ │ │ │ │ We note arm 1 is reachable (by `Pair(Some(0), true)`). +//! │ │ │ │ │ We note arm 1 is useful (by `Pair(Some(0), true)`). //! │ │ │ ├─┘ //! │ │ │ │ //! │ │ │ │ Specialize with `false`: @@ -385,7 +448,7 @@ //! │ │ │ │ │ 1. `[]` //! │ │ │ │ │ 3. `[]` //! │ │ │ │ │ -//! │ │ │ │ │ We note arm 1 is reachable (by `Pair(Some(0), false)`). +//! │ │ │ │ │ We note arm 1 is useful (by `Pair(Some(0), false)`). //! │ │ │ ├─┘ //! │ │ ├─┘ //! │ │ │ @@ -408,7 +471,7 @@ //! │ │ │ ├─┐ Patterns: //! │ │ │ │ │ 2. `[]` //! │ │ │ │ │ -//! │ │ │ │ │ We note arm 2 is reachable (by `Pair(Some(1..), false)`). +//! │ │ │ │ │ We note arm 2 is useful (by `Pair(Some(1..), false)`). //! │ │ │ ├─┘ //! │ │ │ │ //! │ │ │ │ Total witnesses for `1..`: @@ -442,7 +505,7 @@ //! │ │ ├─┐ Patterns: //! │ │ │ │ 2. `[]` //! │ │ │ │ -//! │ │ │ │ We note arm 2 is reachable (by `Pair(None, false)`). +//! │ │ │ │ We note arm 2 is useful (by `Pair(None, false)`). //! │ │ ├─┘ //! │ │ │ //! │ │ │ Total witnesses for `None`: @@ -466,7 +529,7 @@ //! ``` //! //! We conclude: -//! - Arm 3 is unreachable (it was never marked as reachable); +//! - Arm 3 is redundant (it was never marked as useful); //! - The match is not exhaustive; //! - Adding arms with `Pair(Some(1..), true)` and `Pair(None, true)` would make the match exhaustive. //! @@ -639,13 +702,13 @@ struct MatrixRow<'p, 'tcx> { /// Whether the original arm had a guard. This is inherited when specializing. is_under_guard: bool, /// When we specialize, we remember which row of the original matrix produced a given row of the - /// specialized matrix. When we unspecialize, we use this to propagate reachability back up the + /// specialized matrix. When we unspecialize, we use this to propagate usefulness back up the /// callstack. parent_row: usize, /// False when the matrix is just built. This is set to `true` by - /// [`compute_exhaustiveness_and_reachability`] if the arm is found to be reachable. + /// [`compute_exhaustiveness_and_usefulness`] if the arm is found to be useful. /// This is reset to `false` when specializing. - reachable: bool, + useful: bool, } impl<'p, 'tcx> MatrixRow<'p, 'tcx> { @@ -672,7 +735,7 @@ impl<'p, 'tcx> MatrixRow<'p, 'tcx> { pats: patstack, parent_row: self.parent_row, is_under_guard: self.is_under_guard, - reachable: false, + useful: false, }) } @@ -688,7 +751,7 @@ impl<'p, 'tcx> MatrixRow<'p, 'tcx> { pats: self.pats.pop_head_constructor(pcx, ctor), parent_row, is_under_guard: self.is_under_guard, - reachable: false, + useful: false, } } } @@ -741,7 +804,7 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> { pats: PatStack::from_pattern(arm.pat), parent_row: row_id, // dummy, we won't read it is_under_guard: arm.has_guard, - reachable: false, + useful: false, }; matrix.expand_and_push(v); } @@ -940,7 +1003,7 @@ impl<'tcx> WitnessStack<'tcx> { /// Represents a set of pattern-tuples that are witnesses of non-exhaustiveness for error /// reporting. This has similar invariants as `Matrix` does. /// -/// The `WitnessMatrix` returned by [`compute_exhaustiveness_and_reachability`] obeys the invariant +/// The `WitnessMatrix` returned by [`compute_exhaustiveness_and_usefulness`] obeys the invariant /// that the union of the input `Matrix` and the output `WitnessMatrix` together matches the type /// exhaustively. /// @@ -1029,7 +1092,7 @@ impl<'tcx> WitnessMatrix<'tcx> { /// The core of the algorithm. /// /// This recursively computes witnesses of the non-exhaustiveness of `matrix` (if any). Also tracks -/// usefulness of each row in the matrix (in `row.reachable`). We track reachability of each +/// usefulness of each row in the matrix (in `row.useful`). We track usefulness of each /// subpattern using interior mutability in `DeconstructedPat`. /// /// The input `Matrix` and the output `WitnessMatrix` together match the type exhaustively. @@ -1038,10 +1101,10 @@ impl<'tcx> WitnessMatrix<'tcx> { /// - specialization, where we dig into the rows that have a specific constructor and call ourselves /// recursively; /// - unspecialization, where we lift the results from the previous step into results for this step -/// (using `apply_constructor` and by updating `row.reachable` for each parent row). +/// (using `apply_constructor` and by updating `row.useful` for each parent row). /// This is all explained at the top of the file. #[instrument(level = "debug", skip(cx, is_top_level), ret)] -fn compute_exhaustiveness_and_reachability<'p, 'tcx>( +fn compute_exhaustiveness_and_usefulness<'p, 'tcx>( cx: &MatchCheckCtxt<'p, 'tcx>, matrix: &mut Matrix<'p, 'tcx>, is_top_level: bool, @@ -1050,10 +1113,10 @@ fn compute_exhaustiveness_and_reachability<'p, 'tcx>( let Some(ty) = matrix.head_ty() else { // The base case: there are no columns in the matrix. We are morally pattern-matching on (). - // A row is reachable iff it has no (unguarded) rows above it. + // A row is useful iff it has no (unguarded) rows above it. for row in matrix.rows_mut() { - // All rows are reachable until we find one without a guard. - row.reachable = true; + // All rows are useful until they're not. + row.useful = true; if !row.is_under_guard { // There's an unguarded row, so the match is exhaustive, and any subsequent row is // unreachable. @@ -1095,7 +1158,7 @@ fn compute_exhaustiveness_and_reachability<'p, 'tcx>( // Dig into rows that match `ctor`. let mut spec_matrix = matrix.specialize_constructor(pcx, &ctor); let mut witnesses = ensure_sufficient_stack(|| { - compute_exhaustiveness_and_reachability(cx, &mut spec_matrix, false) + compute_exhaustiveness_and_usefulness(cx, &mut spec_matrix, false) }); if !only_report_missing || matches!(ctor, Constructor::Missing) { @@ -1113,14 +1176,14 @@ fn compute_exhaustiveness_and_reachability<'p, 'tcx>( // A parent row is useful if any of its children is. for child_row in spec_matrix.rows() { let parent_row = &mut matrix.rows[child_row.parent_row]; - parent_row.reachable = parent_row.reachable || child_row.reachable; + parent_row.useful = parent_row.useful || child_row.useful; } } - // Record that the subpattern is reachable. + // Record usefulness in the patterns. for row in matrix.rows() { - if row.reachable { - row.head().set_reachable(); + if row.useful { + row.head().set_useful(); } } @@ -1130,8 +1193,8 @@ fn compute_exhaustiveness_and_reachability<'p, 'tcx>( /// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that /// inspect the same subvalue/place". /// This is used to traverse patterns column-by-column for lints. Despite similarities with -/// [`compute_exhaustiveness_and_reachability`], this does a different traversal. Notably this is -/// linear in the depth of patterns, whereas `compute_exhaustiveness_and_reachability` is worst-case +/// [`compute_exhaustiveness_and_usefulness`], this does a different traversal. Notably this is +/// linear in the depth of patterns, whereas `compute_exhaustiveness_and_usefulness` is worst-case /// exponential (exhaustiveness is NP-complete). The core difference is that we treat sub-columns /// separately. /// @@ -1351,28 +1414,29 @@ pub(crate) struct MatchArm<'p, 'tcx> { pub(crate) has_guard: bool, } -/// Indicates whether or not a given arm is reachable. +/// Indicates whether or not a given arm is useful. #[derive(Clone, Debug)] -pub(crate) enum Reachability { - /// The arm is reachable. This additionally carries a set of or-pattern branches that have been - /// found to be unreachable despite the overall arm being reachable. Used only in the presence - /// of or-patterns, otherwise it stays empty. - Reachable(Vec), - /// The arm is unreachable. - Unreachable, +pub(crate) enum Usefulness { + /// The arm is useful. This additionally carries a set of or-pattern branches that have been + /// found to be redundant despite the overall arm being useful. Used only in the presence of + /// or-patterns, otherwise it stays empty. + Useful(Vec), + /// The arm is redundant and can be removed without changing the behavior of the match + /// expression. + Redundant, } -/// The output of checking a match for exhaustiveness and arm reachability. +/// The output of checking a match for exhaustiveness and arm usefulness. pub(crate) struct UsefulnessReport<'p, 'tcx> { - /// For each arm of the input, whether that arm is reachable after the arms above it. - pub(crate) arm_usefulness: Vec<(MatchArm<'p, 'tcx>, Reachability)>, + /// For each arm of the input, whether that arm is useful after the arms above it. + pub(crate) arm_usefulness: Vec<(MatchArm<'p, 'tcx>, Usefulness)>, /// If the match is exhaustive, this is empty. If not, this contains witnesses for the lack of /// exhaustiveness. pub(crate) non_exhaustiveness_witnesses: Vec>, } /// The entrypoint for this file. Computes whether a match is exhaustive and which of its arms are -/// reachable. +/// useful. #[instrument(skip(cx, arms), level = "debug")] pub(crate) fn compute_match_usefulness<'p, 'tcx>( cx: &MatchCheckCtxt<'p, 'tcx>, @@ -1380,8 +1444,7 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>( scrut_ty: Ty<'tcx>, ) -> UsefulnessReport<'p, 'tcx> { let mut matrix = Matrix::new(cx, arms, scrut_ty); - let non_exhaustiveness_witnesses = - compute_exhaustiveness_and_reachability(cx, &mut matrix, true); + let non_exhaustiveness_witnesses = compute_exhaustiveness_and_usefulness(cx, &mut matrix, true); let non_exhaustiveness_witnesses: Vec<_> = non_exhaustiveness_witnesses.single_column(); let arm_usefulness: Vec<_> = arms @@ -1389,12 +1452,13 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>( .copied() .map(|arm| { debug!(?arm); - let reachability = if arm.pat.is_reachable() { - Reachability::Reachable(arm.pat.unreachable_spans()) + // We warn when a pattern is not useful. + let usefulness = if arm.pat.is_useful() { + Usefulness::Useful(arm.pat.redundant_spans()) } else { - Reachability::Unreachable + Usefulness::Redundant }; - (arm, reachability) + (arm, usefulness) }) .collect(); let report = UsefulnessReport { arm_usefulness, non_exhaustiveness_witnesses }; From 2186f98f16242545e09a4996e675738e3bf9209b Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sun, 29 Oct 2023 19:18:18 +0100 Subject: [PATCH 3/7] Correctly handle empty constructors - `ConstructorSet` knows about both empty and nonempty constructors; - If an empty constructor is present in the column, we output it in `split().present`. --- .../src/thir/pattern/deconstruct_pat.rs | 364 ++++++++++-------- .../src/thir/pattern/usefulness.rs | 6 +- 2 files changed, 212 insertions(+), 158 deletions(-) diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs index 094acbc3f8aa0..f1ad0f25cd25c 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs @@ -10,6 +10,7 @@ //! precisely here. //! //! +//! //! # Constructor grouping and splitting //! //! As explained in the corresponding section in [`super::usefulness`], to make usefulness tractable @@ -49,6 +50,7 @@ //! [`IntRange::split`]) and slice splitting (see [`Slice::split`]). //! //! +//! //! # The `Missing` constructor //! //! We detail a special case of constructor splitting that is a bit subtle. Take the following: @@ -77,6 +79,69 @@ //! //! //! +//! ## Empty types, empty constructors, and the `exhaustive_patterns` feature +//! +//! An empty type is a type that has no valid value, like `!`, `enum Void {}`, or `Result`. +//! They require careful handling. +//! +//! First, for soundness reasons related to the possible existence of invalid values, by default we +//! don't treat empty types as empty. We force them to be matched with wildcards. Except if the +//! `exhaustive_patterns` feature is turned on, in which case we do treat them as empty. And also +//! except if the type has no constructors (like `enum Void {}` but not like `Result`), we +//! specifically allow `match void {}` to be exhaustive. There are additionally considerations of +//! place validity that are handled in `super::usefulness`. Yes this is a bit tricky. +//! +//! The second thing is that regardless of the above, it is always allowed to use all the +//! constructors of a type. For example, all the following is ok: +//! +//! ```rust,ignore(example) +//! # #![feature(never_type)] +//! # #![feature(exhaustive_patterns)] +//! fn foo(x: Option) { +//! match x { +//! None => {} +//! Some(_) => {} +//! } +//! } +//! fn bar(x: &[!]) -> u32 { +//! match x { +//! [] => 1, +//! [_] => 2, +//! [_, _] => 3, +//! } +//! } +//! ``` +//! +//! Moreover, take the following: +//! +//! ```rust +//! # #![feature(never_type)] +//! # #![feature(exhaustive_patterns)] +//! # let x = None::; +//! match x { +//! None => {} +//! } +//! ``` +//! +//! On a normal type, we would identify `Some` as missing and tell the user. If `x: Option` +//! however (and `exhaustive_patterns` is on), it's ok to omit `Some`. When listing the constructors +//! of a type, we must therefore track which can be omitted. +//! +//! Let's call "empty" a constructor that matches no valid value for the type, like `Some` for the +//! type `Option`. What this all means is that `ConstructorSet` must know which constructors are +//! empty. The difference between empty and nonempty constructors is that empty constructors need +//! not be present for the match to be exhaustive. +//! +//! A final remark: empty constructors of arity 0 break specialization, we must avoid them. The +//! reason is that if we specialize by them, nothing remains to witness the emptiness; the rest of +//! the algorithm can't distinguish them from a nonempty constructor. The only known case where this +//! could happen is the `[..]` pattern on `[!; N]` with `N > 0` so we must take care to not emit it. +//! +//! This is all handled by [`ConstructorSet::for_ty`] and [`ConstructorSet::split`]. The invariants +//! of [`SplitConstructorSet`] are also of interest. +//! +//! +//! //! ## Opaque patterns //! //! Some patterns, such as constants that are not allowed to be matched structurally, cannot be @@ -95,7 +160,7 @@ use rustc_apfloat::ieee::{DoubleS, IeeeFloat, SingleS}; use rustc_data_structures::captures::Captures; use rustc_data_structures::fx::FxHashSet; use rustc_hir::RangeEnd; -use rustc_index::Idx; +use rustc_index::{Idx, IndexVec}; use rustc_middle::middle::stability::EvalResult; use rustc_middle::mir; use rustc_middle::mir::interpret::Scalar; @@ -482,8 +547,12 @@ pub(super) struct Slice { impl Slice { fn new(array_len: Option, kind: SliceKind) -> Self { let kind = match (array_len, kind) { - // If the middle `..` is empty, we effectively have a fixed-length pattern. - (Some(len), VarLen(prefix, suffix)) if prefix + suffix >= len => FixedLen(len), + // If the middle `..` has length 0, we effectively have a fixed-length pattern. + (Some(len), VarLen(prefix, suffix)) if prefix + suffix == len => FixedLen(len), + (Some(len), VarLen(prefix, suffix)) if prefix + suffix > len => bug!( + "Slice pattern of length {} longer than its array length {len}", + prefix + suffix + ), _ => kind, }; Slice { array_len, kind } @@ -583,17 +652,18 @@ impl Slice { let mut seen_fixed_lens = FxHashSet::default(); match &mut max_slice { VarLen(max_prefix_len, max_suffix_len) => { + // A length larger than any fixed-length slice encountered. + // We start at 1 in case the subtype is empty because in that case the zero-length + // slice must be treated separately from the rest. + let mut fixed_len_upper_bound = 1; // We grow `max_slice` to be larger than all slices encountered, as described above. - // For diagnostics, we keep the prefix and suffix lengths separate, but grow them so that - // `L = max_prefix_len + max_suffix_len`. - let mut max_fixed_len = 0; + // `L` is `max_slice.arity()`. For diagnostics, we keep the prefix and suffix + // lengths separate. for slice in column_slices { match slice.kind { FixedLen(len) => { - max_fixed_len = cmp::max(max_fixed_len, len); - if arity <= len { - seen_fixed_lens.insert(len); - } + fixed_len_upper_bound = cmp::max(fixed_len_upper_bound, len + 1); + seen_fixed_lens.insert(len); } VarLen(prefix, suffix) => { *max_prefix_len = cmp::max(*max_prefix_len, prefix); @@ -602,12 +672,11 @@ impl Slice { } } } - // We want `L = max(L, max_fixed_len + 1)`, modulo the fact that we keep prefix and - // suffix separate. - if max_fixed_len + 1 >= *max_prefix_len + *max_suffix_len { - // The subtraction can't overflow thanks to the above check. - // The new `max_prefix_len` is larger than its previous value. - *max_prefix_len = max_fixed_len + 1 - *max_suffix_len; + // If `fixed_len_upper_bound >= L`, we set `L` to `fixed_len_upper_bound`. + if let Some(delta) = + fixed_len_upper_bound.checked_sub(*max_prefix_len + *max_suffix_len) + { + *max_prefix_len += delta } // We cap the arity of `max_slice` at the array size. @@ -856,34 +925,46 @@ impl<'tcx> Constructor<'tcx> { } } -/// Describes the set of all constructors for a type. +#[derive(Debug, Clone, Copy)] +pub(super) enum VariantVisibility { + /// Variant that doesn't fit the other cases, i.e. most variants. + Visible, + /// Variant behind an unstable gate or with the `#[doc(hidden)]` attribute. It will not be + /// mentioned in diagnostics unless the user mentioned it first. + Hidden, + /// Variant that matches no value. E.g. `Some::>` if the `exhaustive_patterns` feature + /// is enabled. Like `Hidden`, it will not be mentioned in diagnostics unless the user mentioned + /// it first. + Empty, +} + +/// Describes the set of all constructors for a type. For details, in particular about the emptiness +/// of constructors, see the top of the file. +/// +/// In terms of division of responsibility, [`ConstructorSet::split`] handles all of the +/// `exhaustive_patterns` feature. #[derive(Debug)] pub(super) enum ConstructorSet { - /// The type has a single constructor, e.g. `&T` or a struct. - Single, - /// This type has the following list of constructors. - /// Some variants are hidden, which means they won't be mentioned in diagnostics unless the user - /// mentioned them first. We use this for variants behind an unstable gate as well as - /// `#[doc(hidden)]` ones. - Variants { - visible_variants: Vec, - hidden_variants: Vec, - non_exhaustive: bool, - }, + /// The type has a single constructor, e.g. `&T` or a struct. `empty` tracks whether the + /// constructor is empty. + Single { empty: bool }, + /// This type has the following list of constructors. If `variants` is empty and + /// `non_exhaustive` is false, don't use this; use `NoConstructors` instead. + Variants { variants: IndexVec, non_exhaustive: bool }, /// Booleans. Bool, /// The type is spanned by integer values. The range or ranges give the set of allowed values. /// The second range is only useful for `char`. Integers { range_1: IntRange, range_2: Option }, - /// The type is matched by slices. The usize is the compile-time length of the array, if known. - Slice(Option), - /// The type is matched by slices whose elements are uninhabited. - SliceOfEmpty, + /// The type is matched by slices. `array_len` is the compile-time length of the array, if + /// known. If `subtype_is_empty`, all constructors are empty except possibly the zero-length + /// slice `[]`. + Slice { array_len: Option, subtype_is_empty: bool }, /// The constructors cannot be listed, and the type cannot be matched exhaustively. E.g. `str`, /// floats. Unlistable, - /// The type has no inhabitants. - Uninhabited, + /// The type has no constructors (not even empty ones). This is `!` and empty enums. + NoConstructors, } /// Describes the result of analyzing the constructors in a column of a match. @@ -913,6 +994,8 @@ pub(super) struct SplitConstructorSet<'tcx> { impl ConstructorSet { /// Creates a set that represents all the constructors of `ty`. + /// + /// See at the top of the file for considerations of emptiness. #[instrument(level = "debug", skip(cx), ret)] pub(super) fn for_ty<'p, 'tcx>(cx: &MatchCheckCtxt<'p, 'tcx>, ty: Ty<'tcx>) -> Self { let make_range = |start, end| { @@ -924,12 +1007,6 @@ impl ConstructorSet { }; // This determines the set of all possible constructors for the type `ty`. For numbers, // arrays and slices we use ranges and variable-length slices when appropriate. - // - // If the `exhaustive_patterns` feature is enabled, we make sure to omit constructors that - // are statically impossible. E.g., for `Option`, we do not include `Some(_)` in the - // returned list of constructors. - // Invariant: this is `Uninhabited` if and only if the type is uninhabited (as determined by - // `cx.is_uninhabited()`). match ty.kind() { ty::Bool => Self::Bool, ty::Char => { @@ -963,82 +1040,74 @@ impl ConstructorSet { }; Self::Integers { range_1: range, range_2: None } } - ty::Array(sub_ty, len) if len.try_eval_target_usize(cx.tcx, cx.param_env).is_some() => { - let len = len.eval_target_usize(cx.tcx, cx.param_env) as usize; - if len != 0 && cx.is_uninhabited(*sub_ty) { - Self::Uninhabited - } else { - Self::Slice(Some(len)) - } + ty::Slice(sub_ty) => { + Self::Slice { array_len: None, subtype_is_empty: cx.is_uninhabited(*sub_ty) } } - // Treat arrays of a constant but unknown length like slices. - ty::Array(sub_ty, _) | ty::Slice(sub_ty) => { - if cx.is_uninhabited(*sub_ty) { - Self::SliceOfEmpty - } else { - Self::Slice(None) + ty::Array(sub_ty, len) => { + // We treat arrays of a constant but unknown length like slices. + Self::Slice { + array_len: len.try_eval_target_usize(cx.tcx, cx.param_env).map(|l| l as usize), + subtype_is_empty: cx.is_uninhabited(*sub_ty), } } ty::Adt(def, args) if def.is_enum() => { - // If the enum is declared as `#[non_exhaustive]`, we treat it as if it had an - // additional "unknown" constructor. - // There is no point in enumerating all possible variants, because the user can't - // actually match against them all themselves. So we always return only the fictitious - // constructor. - // E.g., in an example like: - // - // ``` - // let err: io::ErrorKind = ...; - // match err { - // io::ErrorKind::NotFound => {}, - // } - // ``` - // - // we don't want to show every possible IO error, but instead have only `_` as the - // witness. let is_declared_nonexhaustive = cx.is_foreign_non_exhaustive_enum(ty); - if def.variants().is_empty() && !is_declared_nonexhaustive { - Self::Uninhabited + Self::NoConstructors } else { - let is_exhaustive_pat_feature = cx.tcx.features().exhaustive_patterns; - let (hidden_variants, visible_variants) = def - .variants() - .iter_enumerated() - .filter(|(_, v)| { - // If `exhaustive_patterns` is enabled, we exclude variants known to be - // uninhabited. - !is_exhaustive_pat_feature - || v.inhabited_predicate(cx.tcx, *def) - .instantiate(cx.tcx, args) - .apply(cx.tcx, cx.param_env, cx.module) - }) - .map(|(idx, _)| idx) - .partition(|idx| { - let variant_def_id = def.variant(*idx).def_id; - // Filter variants that depend on a disabled unstable feature. - let is_unstable = matches!( - cx.tcx.eval_stability(variant_def_id, None, DUMMY_SP, None), - EvalResult::Deny { .. } - ); - // Filter foreign `#[doc(hidden)]` variants. - let is_doc_hidden = - cx.tcx.is_doc_hidden(variant_def_id) && !variant_def_id.is_local(); - is_unstable || is_doc_hidden - }); - - Self::Variants { - visible_variants, - hidden_variants, - non_exhaustive: is_declared_nonexhaustive, + let mut variants = + IndexVec::from_elem(VariantVisibility::Visible, def.variants()); + for (idx, v) in def.variants().iter_enumerated() { + let variant_def_id = def.variant(idx).def_id; + // Visibly uninhabited variants. + let is_inhabited = v + .inhabited_predicate(cx.tcx, *def) + .instantiate(cx.tcx, args) + .apply(cx.tcx, cx.param_env, cx.module); + // Variants that depend on a disabled unstable feature. + let is_unstable = matches!( + cx.tcx.eval_stability(variant_def_id, None, DUMMY_SP, None), + EvalResult::Deny { .. } + ); + // Foreign `#[doc(hidden)]` variants. + let is_doc_hidden = + cx.tcx.is_doc_hidden(variant_def_id) && !variant_def_id.is_local(); + let visibility = if !is_inhabited { + // FIXME: handle empty+hidden + VariantVisibility::Empty + } else if is_unstable || is_doc_hidden { + VariantVisibility::Hidden + } else { + VariantVisibility::Visible + }; + variants[idx] = visibility; } + + Self::Variants { variants, non_exhaustive: is_declared_nonexhaustive } } } - ty::Never => Self::Uninhabited, - _ if cx.is_uninhabited(ty) => Self::Uninhabited, - ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => Self::Single, + ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => { + Self::Single { empty: cx.is_uninhabited(ty) } + } + ty::Never => Self::NoConstructors, // This type is one for which we cannot list constructors, like `str` or `f64`. - _ => Self::Unlistable, + // FIXME(Nadrieril): which of these are actually allowed? + ty::Float(_) + | ty::Str + | ty::Foreign(_) + | ty::RawPtr(_) + | ty::FnDef(_, _) + | ty::FnPtr(_) + | ty::Dynamic(_, _, _) + | ty::Closure(_, _) + | ty::Coroutine(_, _, _) + | ty::CoroutineWitness(_, _) + | ty::Alias(_, _) + | ty::Param(_) + | ty::Bound(_, _) + | ty::Placeholder(_) + | ty::Infer(_) + | ty::Error(_) => Self::Unlistable, } } @@ -1056,6 +1125,9 @@ impl ConstructorSet { 'tcx: 'a, { let mut present: SmallVec<[_; 1]> = SmallVec::new(); + // Empty constructors found missing. + let mut missing_empty = Vec::new(); + // Nonempty constructors found missing. let mut missing = Vec::new(); // Constructors in `ctors`, except wildcards and opaques. let mut seen = Vec::new(); @@ -1068,38 +1140,36 @@ impl ConstructorSet { } match self { - ConstructorSet::Single => { - if seen.is_empty() { - missing.push(Single); - } else { + ConstructorSet::Single { empty } => { + if !seen.is_empty() { present.push(Single); + } else if *empty { + missing_empty.push(Single); + } else { + missing.push(Single); } } - ConstructorSet::Variants { visible_variants, hidden_variants, non_exhaustive } => { + ConstructorSet::Variants { variants, non_exhaustive } => { let seen_set: FxHashSet<_> = seen.iter().map(|c| c.as_variant().unwrap()).collect(); let mut skipped_a_hidden_variant = false; - for variant in visible_variants { - let ctor = Variant(*variant); - if seen_set.contains(variant) { + for (idx, visibility) in variants.iter_enumerated() { + let ctor = Variant(idx); + if seen_set.contains(&idx) { present.push(ctor); } else { - missing.push(ctor); + // We only put visible variants directly into `missing`. + match visibility { + VariantVisibility::Visible => missing.push(ctor), + VariantVisibility::Hidden => skipped_a_hidden_variant = true, + VariantVisibility::Empty => missing_empty.push(ctor), + } } } - for variant in hidden_variants { - let ctor = Variant(*variant); - if seen_set.contains(variant) { - present.push(ctor); - } else { - skipped_a_hidden_variant = true; - } - } if skipped_a_hidden_variant { missing.push(Hidden); } - if *non_exhaustive { missing.push(NonExhaustive); } @@ -1143,33 +1213,22 @@ impl ConstructorSet { } } } - &ConstructorSet::Slice(array_len) => { + ConstructorSet::Slice { array_len, subtype_is_empty } => { let seen_slices = seen.iter().map(|c| c.as_slice().unwrap()); - let base_slice = Slice::new(array_len, VarLen(0, 0)); + let base_slice = Slice::new(*array_len, VarLen(0, 0)); for (seen, splitted_slice) in base_slice.split(seen_slices) { let ctor = Slice(splitted_slice); match seen { - Presence::Unseen => missing.push(ctor), Presence::Seen => present.push(ctor), - } - } - } - ConstructorSet::SliceOfEmpty => { - // This one is tricky because even though there's only one possible value of this - // type (namely `[]`), slice patterns of all lengths are allowed, they're just - // unreachable if length != 0. - // We still gather the seen constructors in `present`, but the only slice that can - // go in `missing` is `[]`. - let seen_slices = seen.iter().map(|c| c.as_slice().unwrap()); - let base_slice = Slice::new(None, VarLen(0, 0)); - for (seen, splitted_slice) in base_slice.split(seen_slices) { - let ctor = Slice(splitted_slice); - match seen { - Presence::Seen => present.push(ctor), - Presence::Unseen if splitted_slice.arity() == 0 => { - missing.push(Slice(Slice::new(None, FixedLen(0)))) + Presence::Unseen => { + if *subtype_is_empty && splitted_slice.arity() != 0 { + // We have subpatterns of an empty type, so the constructor is + // empty. + missing_empty.push(ctor); + } else { + missing.push(ctor); + } } - Presence::Unseen => {} } } } @@ -1179,17 +1238,16 @@ impl ConstructorSet { present.extend(seen); missing.push(NonExhaustive); } - // If `exhaustive_patterns` is disabled and our scrutinee is an empty type, we cannot - // expose its emptiness. The exception is if the pattern is at the top level, because we - // want empty matches to be considered exhaustive. - ConstructorSet::Uninhabited - if !pcx.cx.tcx.features().exhaustive_patterns && !pcx.is_top_level => - { - missing.push(NonExhaustive); + ConstructorSet::NoConstructors => { + if !pcx.is_top_level { + missing_empty.push(NonExhaustive); + } } - ConstructorSet::Uninhabited => {} } + if !pcx.cx.tcx.features().exhaustive_patterns { + missing.extend(missing_empty); + } SplitConstructorSet { present, missing } } } @@ -1263,7 +1321,7 @@ impl<'p, 'tcx> Fields<'p, 'tcx> { // `field.ty()` doesn't normalize after substituting. let ty = cx.tcx.normalize_erasing_regions(cx.param_env, ty); let is_visible = adt.is_enum() || field.vis.is_accessible_from(cx.module, cx.tcx); - let is_uninhabited = cx.is_uninhabited(ty); + let is_uninhabited = cx.tcx.features().exhaustive_patterns && cx.is_uninhabited(ty); if is_uninhabited && (!is_visible || is_non_exhaustive) { None diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs index e77f158a980ab..38a66522ac699 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs @@ -596,11 +596,7 @@ pub(crate) struct MatchCheckCtxt<'p, 'tcx> { impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> { pub(super) fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool { - if self.tcx.features().exhaustive_patterns { - !ty.is_inhabited_from(self.tcx, self.module, self.param_env) - } else { - false - } + !ty.is_inhabited_from(self.tcx, self.module, self.param_env) } /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`. From 1978168c136ba65b8da3f5a45834631c13d7c56f Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sun, 26 Nov 2023 12:54:52 +0100 Subject: [PATCH 4/7] Detect cycles in `InhabitedPredicate::apply` This is for post-monomorphization cycles. These are only caught later (in drop elaboration for the example that I saw), so we need to handle them here. This issue wasn't noticed before because exhaustiveness only checked inhabitedness when `exhaustive_patterns` was on. The preceding commit now check inhabitedness always, which revealed the problem. --- .../ty/inhabitedness/inhabited_predicate.rs | 40 ++++++++++++++----- .../rustc_middle/src/ty/inhabitedness/mod.rs | 1 + 2 files changed, 31 insertions(+), 10 deletions(-) diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs index f278cace99dc4..ae17942785ff8 100644 --- a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs +++ b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs @@ -1,3 +1,5 @@ +use smallvec::SmallVec; + use crate::ty::context::TyCtxt; use crate::ty::{self, DefId, ParamEnv, Ty}; @@ -31,27 +33,31 @@ impl<'tcx> InhabitedPredicate<'tcx> { /// Returns true if the corresponding type is inhabited in the given /// `ParamEnv` and module pub fn apply(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, module_def_id: DefId) -> bool { - let Ok(result) = self - .apply_inner::(tcx, param_env, &|id| Ok(tcx.is_descendant_of(module_def_id, id))); + let Ok(result) = self.apply_inner::(tcx, param_env, &mut Default::default(), &|id| { + Ok(tcx.is_descendant_of(module_def_id, id)) + }); result } /// Same as `apply`, but returns `None` if self contains a module predicate pub fn apply_any_module(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option { - self.apply_inner(tcx, param_env, &|_| Err(())).ok() + self.apply_inner(tcx, param_env, &mut Default::default(), &|_| Err(())).ok() } /// Same as `apply`, but `NotInModule(_)` predicates yield `false`. That is, /// privately uninhabited types are considered always uninhabited. pub fn apply_ignore_module(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> bool { - let Ok(result) = self.apply_inner::(tcx, param_env, &|_| Ok(true)); + let Ok(result) = + self.apply_inner::(tcx, param_env, &mut Default::default(), &|_| Ok(true)); result } - fn apply_inner( + #[instrument(level = "debug", skip(tcx, param_env, in_module), ret)] + fn apply_inner( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, + eval_stack: &mut SmallVec<[Ty<'tcx>; 1]>, // for cycle detection in_module: &impl Fn(DefId) -> Result, ) -> Result { match self { @@ -71,11 +77,25 @@ impl<'tcx> InhabitedPredicate<'tcx> { match normalized_pred { // We don't have more information than we started with, so consider inhabited. Self::GenericType(_) => Ok(true), - pred => pred.apply_inner(tcx, param_env, in_module), + pred => { + // A type which is cyclic when monomorphized can happen here since the + // layout error would only trigger later. See e.g. `tests/ui/sized/recursive-type-2.rs`. + if eval_stack.contains(&t) { + return Ok(true); // Recover; this will error later. + } + eval_stack.push(t); + let ret = pred.apply_inner(tcx, param_env, eval_stack, in_module); + eval_stack.pop(); + ret + } } } - Self::And([a, b]) => try_and(a, b, |x| x.apply_inner(tcx, param_env, in_module)), - Self::Or([a, b]) => try_or(a, b, |x| x.apply_inner(tcx, param_env, in_module)), + Self::And([a, b]) => { + try_and(a, b, |x| x.apply_inner(tcx, param_env, eval_stack, in_module)) + } + Self::Or([a, b]) => { + try_or(a, b, |x| x.apply_inner(tcx, param_env, eval_stack, in_module)) + } } } @@ -197,7 +217,7 @@ impl<'tcx> InhabitedPredicate<'tcx> { // this is basically like `f(a)? && f(b)?` but different in the case of // `Ok(false) && Err(_) -> Ok(false)` -fn try_and(a: T, b: T, f: impl Fn(T) -> Result) -> Result { +fn try_and(a: T, b: T, mut f: impl FnMut(T) -> Result) -> Result { let a = f(a); if matches!(a, Ok(false)) { return Ok(false); @@ -209,7 +229,7 @@ fn try_and(a: T, b: T, f: impl Fn(T) -> Result) -> Result(a: T, b: T, f: impl Fn(T) -> Result) -> Result { +fn try_or(a: T, b: T, mut f: impl FnMut(T) -> Result) -> Result { let a = f(a); if matches!(a, Ok(true)) { return Ok(true); diff --git a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs index 68ac54e899ac3..d67fb9fd0b734 100644 --- a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs +++ b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs @@ -103,6 +103,7 @@ impl<'tcx> VariantDef { } impl<'tcx> Ty<'tcx> { + #[instrument(level = "debug", skip(tcx), ret)] pub fn inhabited_predicate(self, tcx: TyCtxt<'tcx>) -> InhabitedPredicate<'tcx> { match self.kind() { // For now, unions are always considered inhabited From f5dbb54648e40f3363321cd5ea6cd903db1af994 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sat, 18 Nov 2023 03:52:54 +0100 Subject: [PATCH 5/7] Track place validity --- .../src/thir/pattern/check_match.rs | 124 ++++++++++++++++-- .../src/thir/pattern/usefulness.rs | 122 ++++++++++++++--- 2 files changed, 216 insertions(+), 30 deletions(-) diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs index 89b7b3619bebd..41510d31530ad 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs @@ -42,7 +42,7 @@ pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), Err for param in thir.params.iter() { if let Some(box ref pattern) = param.pat { - visitor.check_binding_is_irrefutable(pattern, "function argument", None); + visitor.check_binding_is_irrefutable(pattern, "function argument", None, None); } } visitor.error @@ -254,10 +254,11 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> { self.with_lint_level(lint_level, |this| this.visit_land_rhs(&this.thir[value])) } ExprKind::Let { box ref pat, expr } => { + let expr = &self.thir()[expr]; self.with_let_source(LetSource::None, |this| { - this.visit_expr(&this.thir()[expr]); + this.visit_expr(expr); }); - Ok(Some((ex.span, self.is_let_irrefutable(pat)?))) + Ok(Some((ex.span, self.is_let_irrefutable(pat, Some(expr))?))) } _ => { self.with_let_source(LetSource::None, |this| { @@ -287,35 +288,114 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> { } } + /// Inspects the match scrutinee expression to determine whether the place it evaluates to may + /// hold invalid data. + fn is_known_valid_scrutinee(&self, scrutinee: &Expr<'tcx>) -> bool { + use ExprKind::*; + match &scrutinee.kind { + // Both pointers and references can validly point to a place with invalid data. + Deref { .. } => false, + // Inherit validity of the parent place, unless the parent is an union. + Field { lhs, .. } => { + let lhs = &self.thir()[*lhs]; + match lhs.ty.kind() { + ty::Adt(def, _) if def.is_union() => false, + _ => self.is_known_valid_scrutinee(lhs), + } + } + // Essentially a field access. + Index { lhs, .. } => { + let lhs = &self.thir()[*lhs]; + self.is_known_valid_scrutinee(lhs) + } + + // No-op. + Scope { value, .. } => self.is_known_valid_scrutinee(&self.thir()[*value]), + + // Casts don't cause a load. + NeverToAny { source } + | Cast { source } + | Use { source } + | PointerCoercion { source, .. } + | PlaceTypeAscription { source, .. } + | ValueTypeAscription { source, .. } => { + self.is_known_valid_scrutinee(&self.thir()[*source]) + } + + // These diverge. + Become { .. } | Break { .. } | Continue { .. } | Return { .. } => true, + + // These are statements that evaluate to `()`. + Assign { .. } | AssignOp { .. } | InlineAsm { .. } | Let { .. } => true, + + // These evaluate to a value. + AddressOf { .. } + | Adt { .. } + | Array { .. } + | Binary { .. } + | Block { .. } + | Borrow { .. } + | Box { .. } + | Call { .. } + | Closure { .. } + | ConstBlock { .. } + | ConstParam { .. } + | If { .. } + | Literal { .. } + | LogicalOp { .. } + | Loop { .. } + | Match { .. } + | NamedConst { .. } + | NonHirLiteral { .. } + | OffsetOf { .. } + | Repeat { .. } + | StaticRef { .. } + | ThreadLocalRef { .. } + | Tuple { .. } + | Unary { .. } + | UpvarRef { .. } + | VarRef { .. } + | ZstLiteral { .. } + | Yield { .. } => true, + } + } + fn new_cx( &self, refutability: RefutableFlag, - match_span: Option, + whole_match_span: Option, + scrutinee: Option<&Expr<'tcx>>, scrut_span: Span, ) -> MatchCheckCtxt<'p, 'tcx> { let refutable = match refutability { Irrefutable => false, Refutable => true, }; + // If we don't have a scrutinee we're either a function parameter or a `let x;`. Both cases + // require validity. + let known_valid_scrutinee = + scrutinee.map(|scrut| self.is_known_valid_scrutinee(scrut)).unwrap_or(true); MatchCheckCtxt { tcx: self.tcx, param_env: self.param_env, module: self.tcx.parent_module(self.lint_level).to_def_id(), pattern_arena: self.pattern_arena, match_lint_level: self.lint_level, - match_span, + whole_match_span, scrut_span, refutable, + known_valid_scrutinee, } } #[instrument(level = "trace", skip(self))] fn check_let(&mut self, pat: &Pat<'tcx>, scrutinee: Option, span: Span) { assert!(self.let_source != LetSource::None); + let scrut = scrutinee.map(|id| &self.thir[id]); if let LetSource::PlainLet = self.let_source { - self.check_binding_is_irrefutable(pat, "local binding", Some(span)) + self.check_binding_is_irrefutable(pat, "local binding", scrut, Some(span)) } else { - let Ok(refutability) = self.is_let_irrefutable(pat) else { return }; + let Ok(refutability) = self.is_let_irrefutable(pat, scrut) else { return }; if matches!(refutability, Irrefutable) { report_irrefutable_let_patterns( self.tcx, @@ -336,7 +416,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> { expr_span: Span, ) { let scrut = &self.thir[scrut]; - let cx = self.new_cx(Refutable, Some(expr_span), scrut.span); + let cx = self.new_cx(Refutable, Some(expr_span), Some(scrut), scrut.span); let mut tarms = Vec::with_capacity(arms.len()); for &arm in arms { @@ -377,7 +457,12 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> { debug_assert_eq!(pat.span.desugaring_kind(), Some(DesugaringKind::ForLoop)); let PatKind::Variant { ref subpatterns, .. } = pat.kind else { bug!() }; let [pat_field] = &subpatterns[..] else { bug!() }; - self.check_binding_is_irrefutable(&pat_field.pattern, "`for` loop binding", None); + self.check_binding_is_irrefutable( + &pat_field.pattern, + "`for` loop binding", + None, + None, + ); } else { self.error = Err(report_non_exhaustive_match( &cx, self.thir, scrut_ty, scrut.span, witnesses, arms, expr_span, @@ -457,16 +542,21 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> { &mut self, pat: &Pat<'tcx>, refutability: RefutableFlag, + scrut: Option<&Expr<'tcx>>, ) -> Result<(MatchCheckCtxt<'p, 'tcx>, UsefulnessReport<'p, 'tcx>), ErrorGuaranteed> { - let cx = self.new_cx(refutability, None, pat.span); + let cx = self.new_cx(refutability, None, scrut, pat.span); let pat = self.lower_pattern(&cx, pat)?; let arms = [MatchArm { pat, hir_id: self.lint_level, has_guard: false }]; let report = compute_match_usefulness(&cx, &arms, pat.ty()); Ok((cx, report)) } - fn is_let_irrefutable(&mut self, pat: &Pat<'tcx>) -> Result { - let (cx, report) = self.analyze_binding(pat, Refutable)?; + fn is_let_irrefutable( + &mut self, + pat: &Pat<'tcx>, + scrut: Option<&Expr<'tcx>>, + ) -> Result { + let (cx, report) = self.analyze_binding(pat, Refutable, scrut)?; // Report if the pattern is unreachable, which can only occur when the type is uninhabited. // This also reports unreachable sub-patterns. report_arm_reachability(&cx, &report); @@ -476,10 +566,16 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> { } #[instrument(level = "trace", skip(self))] - fn check_binding_is_irrefutable(&mut self, pat: &Pat<'tcx>, origin: &str, sp: Option) { + fn check_binding_is_irrefutable( + &mut self, + pat: &Pat<'tcx>, + origin: &str, + scrut: Option<&Expr<'tcx>>, + sp: Option, + ) { let pattern_ty = pat.ty; - let Ok((cx, report)) = self.analyze_binding(pat, Irrefutable) else { return }; + let Ok((cx, report)) = self.analyze_binding(pat, Irrefutable, scrut) else { return }; let witnesses = report.non_exhaustiveness_witnesses; if witnesses.is_empty() { // The pattern is irrefutable. diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs index 38a66522ac699..d86147b46990e 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs @@ -551,6 +551,7 @@ //! I (Nadrieril) prefer to put new tests in `ui/pattern/usefulness` unless there's a specific //! reason not to, for example if they crucially depend on a particular feature like `or_patterns`. +use self::ValidityConstraint::*; use super::deconstruct_pat::{ Constructor, ConstructorSet, DeconstructedPat, IntRange, MaybeInfiniteInt, SplitConstructorSet, WitnessPat, @@ -587,11 +588,14 @@ pub(crate) struct MatchCheckCtxt<'p, 'tcx> { /// Lint level at the match. pub(crate) match_lint_level: HirId, /// The span of the whole match, if applicable. - pub(crate) match_span: Option, + pub(crate) whole_match_span: Option, /// Span of the scrutinee. pub(crate) scrut_span: Span, /// Only produce `NON_EXHAUSTIVE_OMITTED_PATTERNS` lint on refutable patterns. pub(crate) refutable: bool, + /// Whether the data at the scrutinee is known to be valid. This is false if the scrutinee comes + /// from a union field, a pointer deref, or a reference deref (pending opsem decisions). + pub(crate) known_valid_scrutinee: bool, } impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> { @@ -620,12 +624,63 @@ pub(super) struct PatCtxt<'a, 'p, 'tcx> { pub(super) is_top_level: bool, } +impl<'a, 'p, 'tcx> PatCtxt<'a, 'p, 'tcx> { + /// A `PatCtxt` when code other than `is_useful` needs one. + fn new_dummy(cx: &'a MatchCheckCtxt<'p, 'tcx>, ty: Ty<'tcx>) -> Self { + PatCtxt { cx, ty, is_top_level: false } + } +} + impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_struct("PatCtxt").field("ty", &self.ty).finish() } } +/// In the matrix, tracks whether a given place (aka column) is known to contain a valid value or +/// not. +#[derive(Debug, Copy, Clone, PartialEq, Eq)] +pub(super) enum ValidityConstraint { + ValidOnly, + MaybeInvalid, +} + +impl ValidityConstraint { + pub(super) fn from_bool(is_valid_only: bool) -> Self { + if is_valid_only { ValidOnly } else { MaybeInvalid } + } + + /// If the place has validity given by `self` and we read that the value at the place has + /// constructor `ctor`, this computes what we can assume about the validity of the constructor + /// fields. + /// + /// Pending further opsem decisions, the current behavior is: validity is preserved, except + /// under `&` where validity is reset to `MaybeInvalid`. + pub(super) fn specialize<'tcx>( + self, + pcx: &PatCtxt<'_, '_, 'tcx>, + ctor: &Constructor<'tcx>, + ) -> Self { + // We preserve validity except when we go under a reference. + if matches!(ctor, Constructor::Single) && matches!(pcx.ty.kind(), ty::Ref(..)) { + // Validity of `x: &T` does not imply validity of `*x: T`. + MaybeInvalid + } else { + self + } + } +} + +impl fmt::Display for ValidityConstraint { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + let s = match self { + ValidOnly => "✓", + MaybeInvalid => "?", + }; + write!(f, "{s}") + } +} + /// Represents a pattern-tuple under investigation. #[derive(Clone)] struct PatStack<'p, 'tcx> { @@ -770,10 +825,15 @@ impl<'p, 'tcx> fmt::Debug for MatrixRow<'p, 'tcx> { /// the matrix will correspond to `scrutinee.0.Some.0` and the second column to `scrutinee.1`. #[derive(Clone)] struct Matrix<'p, 'tcx> { + /// Vector of rows. The rows must form a rectangular 2D array. Moreover, all the patterns of + /// each column must have the same type. Each column corresponds to a place within the + /// scrutinee. rows: Vec>, /// Stores an extra fictitious row full of wildcards. Mostly used to keep track of the type of /// each column. This must obey the same invariants as the real rows. wildcard_row: PatStack<'p, 'tcx>, + /// Track for each column/place whether it contains a known valid value. + place_validity: SmallVec<[ValidityConstraint; 2]>, } impl<'p, 'tcx> Matrix<'p, 'tcx> { @@ -791,10 +851,22 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> { } /// Build a new matrix from an iterator of `MatchArm`s. - fn new(cx: &MatchCheckCtxt<'p, 'tcx>, arms: &[MatchArm<'p, 'tcx>], scrut_ty: Ty<'tcx>) -> Self { + fn new<'a>( + cx: &MatchCheckCtxt<'p, 'tcx>, + arms: &[MatchArm<'p, 'tcx>], + scrut_ty: Ty<'tcx>, + scrut_validity: ValidityConstraint, + ) -> Self + where + 'p: 'a, + { let wild_pattern = cx.pattern_arena.alloc(DeconstructedPat::wildcard(scrut_ty, DUMMY_SP)); let wildcard_row = PatStack::from_pattern(wild_pattern); - let mut matrix = Matrix { rows: Vec::with_capacity(arms.len()), wildcard_row }; + let mut matrix = Matrix { + rows: Vec::with_capacity(arms.len()), + wildcard_row, + place_validity: smallvec![scrut_validity], + }; for (row_id, arm) in arms.iter().enumerate() { let v = MatrixRow { pats: PatStack::from_pattern(arm.pat), @@ -858,7 +930,13 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> { ctor: &Constructor<'tcx>, ) -> Matrix<'p, 'tcx> { let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor); - let mut matrix = Matrix { rows: Vec::new(), wildcard_row }; + let new_validity = self.place_validity[0].specialize(pcx, ctor); + let new_place_validity = std::iter::repeat(new_validity) + .take(ctor.arity(pcx)) + .chain(self.place_validity[1..].iter().copied()) + .collect(); + let mut matrix = + Matrix { rows: Vec::new(), wildcard_row, place_validity: new_place_validity }; for (i, row) in self.rows().enumerate() { if ctor.is_covered_by(pcx, row.head().ctor()) { let new_row = row.pop_head_constructor(pcx, ctor, i); @@ -877,27 +955,38 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> { /// + true + [Second(true)] + /// + false + [_] + /// + _ + [_, _, tail @ ..] + +/// | ✓ | ? | // column validity /// ``` impl<'p, 'tcx> fmt::Debug for Matrix<'p, 'tcx> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "\n")?; - let Matrix { rows, .. } = self; - let pretty_printed_matrix: Vec> = - rows.iter().map(|row| row.iter().map(|pat| format!("{pat:?}")).collect()).collect(); + let mut pretty_printed_matrix: Vec> = self + .rows + .iter() + .map(|row| row.iter().map(|pat| format!("{pat:?}")).collect()) + .collect(); + pretty_printed_matrix + .push(self.place_validity.iter().map(|validity| format!("{validity}")).collect()); - let column_count = rows.iter().map(|row| row.len()).next().unwrap_or(0); - assert!(rows.iter().all(|row| row.len() == column_count)); + let column_count = self.column_count(); + assert!(self.rows.iter().all(|row| row.len() == column_count)); + assert!(self.place_validity.len() == column_count); let column_widths: Vec = (0..column_count) .map(|col| pretty_printed_matrix.iter().map(|row| row[col].len()).max().unwrap_or(0)) .collect(); - for row in pretty_printed_matrix { - write!(f, "+")?; + for (row_i, row) in pretty_printed_matrix.into_iter().enumerate() { + let is_validity_row = row_i == self.rows.len(); + let sep = if is_validity_row { "|" } else { "+" }; + write!(f, "{sep}")?; for (column, pat_str) in row.into_iter().enumerate() { write!(f, " ")?; write!(f, "{:1$}", pat_str, column_widths[column])?; - write!(f, " +")?; + write!(f, " {sep}")?; + } + if is_validity_row { + write!(f, " // column validity")?; } write!(f, "\n")?; } @@ -1287,7 +1376,7 @@ fn collect_nonexhaustive_missing_variants<'p, 'tcx>( let Some(ty) = column.head_ty() else { return Vec::new(); }; - let pcx = &PatCtxt { cx, ty, is_top_level: false }; + let pcx = &PatCtxt::new_dummy(cx, ty); let set = column.analyze_ctors(pcx); if set.present.is_empty() { @@ -1336,7 +1425,7 @@ fn lint_overlapping_range_endpoints<'p, 'tcx>( let Some(ty) = column.head_ty() else { return; }; - let pcx = &PatCtxt { cx, ty, is_top_level: false }; + let pcx = &PatCtxt::new_dummy(cx, ty); let set = column.analyze_ctors(pcx); @@ -1439,7 +1528,8 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>( arms: &[MatchArm<'p, 'tcx>], scrut_ty: Ty<'tcx>, ) -> UsefulnessReport<'p, 'tcx> { - let mut matrix = Matrix::new(cx, arms, scrut_ty); + let scrut_validity = ValidityConstraint::from_bool(cx.known_valid_scrutinee); + let mut matrix = Matrix::new(cx, arms, scrut_ty, scrut_validity); let non_exhaustiveness_witnesses = compute_exhaustiveness_and_usefulness(cx, &mut matrix, true); let non_exhaustiveness_witnesses: Vec<_> = non_exhaustiveness_witnesses.single_column(); @@ -1496,7 +1586,7 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>( if !matches!(lint_level, rustc_session::lint::Level::Allow) { let decorator = NonExhaustiveOmittedPatternLintOnArm { lint_span: lint_level_source.span(), - suggest_lint_on_match: cx.match_span.map(|span| span.shrink_to_lo()), + suggest_lint_on_match: cx.whole_match_span.map(|span| span.shrink_to_lo()), lint_level: lint_level.as_str(), lint_name: "non_exhaustive_omitted_patterns", }; From ddef5b61f134834c81f8802d07ce3774e46143f6 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sat, 18 Nov 2023 21:39:57 +0100 Subject: [PATCH 6/7] Don't warn an empty pattern unreachable if we're not sure the data is valid --- .../src/thir/pattern/deconstruct_pat.rs | 44 +- .../src/thir/pattern/usefulness.rs | 85 +++- .../empty-types.exhaustive_patterns.stderr | 389 +----------------- .../usefulness/empty-types.normal.stderr | 130 +----- tests/ui/pattern/usefulness/empty-types.rs | 128 +++--- tests/ui/pattern/usefulness/slice_of_empty.rs | 6 +- .../pattern/usefulness/slice_of_empty.stderr | 31 +- tests/ui/uninhabited/uninhabited-patterns.rs | 4 +- .../uninhabited/uninhabited-patterns.stderr | 20 +- 9 files changed, 183 insertions(+), 654 deletions(-) diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs index f1ad0f25cd25c..e66402a7eb3ba 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs @@ -787,9 +787,6 @@ pub(super) enum Constructor<'tcx> { } impl<'tcx> Constructor<'tcx> { - pub(super) fn is_wildcard(&self) -> bool { - matches!(self, Wildcard) - } pub(super) fn is_non_exhaustive(&self) -> bool { matches!(self, NonExhaustive) } @@ -973,15 +970,17 @@ pub(super) enum ConstructorSet { /// constructors that exist in the type but are not present in the column. /// /// More formally, if we discard wildcards from the column, this respects the following constraints: -/// 1. the union of `present` and `missing` covers the whole type +/// 1. the union of `present`, `missing` and `missing_empty` covers all the constructors of the type /// 2. each constructor in `present` is covered by something in the column -/// 3. no constructor in `missing` is covered by anything in the column +/// 3. no constructor in `missing` or `missing_empty` is covered by anything in the column /// 4. each constructor in the column is equal to the union of one or more constructors in `present` /// 5. `missing` does not contain empty constructors (see discussion about emptiness at the top of /// the file); -/// 6. constructors in `present` and `missing` are split for the column; in other words, they are -/// either fully included in or fully disjoint from each constructor in the column. In other -/// words, there are no non-trivial intersections like between `0..10` and `5..15`. +/// 6. `missing_empty` contains only empty constructors +/// 7. constructors in `present`, `missing` and `missing_empty` are split for the column; in other +/// words, they are either fully included in or fully disjoint from each constructor in the +/// column. In yet other words, there are no non-trivial intersections like between `0..10` and +/// `5..15`. /// /// We must be particularly careful with weird constructors like `Opaque`: they're not formally part /// of the `ConstructorSet` for the type, yet if we forgot to include them in `present` we would be @@ -990,6 +989,7 @@ pub(super) enum ConstructorSet { pub(super) struct SplitConstructorSet<'tcx> { pub(super) present: SmallVec<[Constructor<'tcx>; 1]>, pub(super) missing: Vec>, + pub(super) missing_empty: Vec>, } impl ConstructorSet { @@ -1132,10 +1132,10 @@ impl ConstructorSet { // Constructors in `ctors`, except wildcards and opaques. let mut seen = Vec::new(); for ctor in ctors.cloned() { - if let Constructor::Opaque(..) = ctor { - present.push(ctor); - } else if !ctor.is_wildcard() { - seen.push(ctor); + match ctor { + Opaque(..) => present.push(ctor), + Wildcard => {} // discard wildcards + _ => seen.push(ctor), } } @@ -1239,16 +1239,24 @@ impl ConstructorSet { missing.push(NonExhaustive); } ConstructorSet::NoConstructors => { - if !pcx.is_top_level { - missing_empty.push(NonExhaustive); - } + // In a `MaybeInvalid` place even an empty pattern may be reachable. We therefore + // add a dummy empty constructor here, which will be ignored if the place is + // `ValidOnly`. + missing_empty.push(NonExhaustive); } } - if !pcx.cx.tcx.features().exhaustive_patterns { - missing.extend(missing_empty); + // We have now grouped all the constructors into 3 buckets: present, missing, missing_empty. + // In the absence of the `exhaustive_patterns` feature however, we don't count nested empty + // types as empty. Only non-nested `!` or `enum Foo {}` are considered empty. + if !pcx.cx.tcx.features().exhaustive_patterns + && !(pcx.is_top_level && matches!(self, Self::NoConstructors)) + { + // Treat all missing constructors as nonempty. + missing.extend(missing_empty.drain(..)); } - SplitConstructorSet { present, missing } + + SplitConstructorSet { present, missing, missing_empty } } } diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs index d86147b46990e..637cc38be2c7c 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs @@ -637,12 +637,18 @@ impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> { } } -/// In the matrix, tracks whether a given place (aka column) is known to contain a valid value or -/// not. +/// Serves two purposes: +/// - in a wildcard, tracks whether the wildcard matches only valid values (i.e. is a binding `_a`) +/// or also invalid values (i.e. is a true `_` pattern). +/// - in the matrix, track whether a given place (aka column) is known to contain a valid value or +/// not. #[derive(Debug, Copy, Clone, PartialEq, Eq)] pub(super) enum ValidityConstraint { ValidOnly, MaybeInvalid, + /// Option for backwards compatibility: the place is not known to be valid but we allow omitting + /// `useful && !reachable` arms anyway. + MaybeInvalidButAllowOmittingArms, } impl ValidityConstraint { @@ -650,19 +656,37 @@ impl ValidityConstraint { if is_valid_only { ValidOnly } else { MaybeInvalid } } + fn allow_omitting_side_effecting_arms(self) -> Self { + match self { + MaybeInvalid | MaybeInvalidButAllowOmittingArms => MaybeInvalidButAllowOmittingArms, + // There are no side-effecting empty arms here, nothing to do. + ValidOnly => ValidOnly, + } + } + + pub(super) fn is_known_valid(self) -> bool { + matches!(self, ValidOnly) + } + pub(super) fn allows_omitting_empty_arms(self) -> bool { + matches!(self, ValidOnly | MaybeInvalidButAllowOmittingArms) + } + /// If the place has validity given by `self` and we read that the value at the place has /// constructor `ctor`, this computes what we can assume about the validity of the constructor /// fields. /// /// Pending further opsem decisions, the current behavior is: validity is preserved, except - /// under `&` where validity is reset to `MaybeInvalid`. + /// inside `&` and union fields where validity is reset to `MaybeInvalid`. pub(super) fn specialize<'tcx>( self, pcx: &PatCtxt<'_, '_, 'tcx>, ctor: &Constructor<'tcx>, ) -> Self { - // We preserve validity except when we go under a reference. - if matches!(ctor, Constructor::Single) && matches!(pcx.ty.kind(), ty::Ref(..)) { + // We preserve validity except when we go inside a reference or a union field. + if matches!(ctor, Constructor::Single) + && (matches!(pcx.ty.kind(), ty::Ref(..)) + || matches!(pcx.ty.kind(), ty::Adt(def, ..) if def.is_union())) + { // Validity of `x: &T` does not imply validity of `*x: T`. MaybeInvalid } else { @@ -675,7 +699,7 @@ impl fmt::Display for ValidityConstraint { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { let s = match self { ValidOnly => "✓", - MaybeInvalid => "?", + MaybeInvalid | MaybeInvalidButAllowOmittingArms => "?", }; write!(f, "{s}") } @@ -1202,9 +1226,9 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>( for row in matrix.rows_mut() { // All rows are useful until they're not. row.useful = true; + // When there's an unguarded row, the match is exhaustive and any subsequent row is not + // useful. if !row.is_under_guard { - // There's an unguarded row, so the match is exhaustive, and any subsequent row is - // unreachable. return WitnessMatrix::empty(); } } @@ -1215,26 +1239,37 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>( debug!("ty: {ty:?}"); let pcx = &PatCtxt { cx, ty, is_top_level }; + // Whether the place/column we are inspecting is known to contain valid data. + let place_validity = matrix.place_validity[0]; + // For backwards compability we allow omitting some empty arms that we ideally shouldn't. + let place_validity = place_validity.allow_omitting_side_effecting_arms(); + // Analyze the constructors present in this column. let ctors = matrix.heads().map(|p| p.ctor()); - let split_set = ConstructorSet::for_ty(pcx.cx, pcx.ty).split(pcx, ctors); - + let split_set = ConstructorSet::for_ty(cx, ty).split(pcx, ctors); let all_missing = split_set.present.is_empty(); - let always_report_all = is_top_level && !IntRange::is_integral(pcx.ty); - // Whether we should report "Enum::A and Enum::C are missing" or "_ is missing". - let report_individual_missing_ctors = always_report_all || !all_missing; + // Build the set of constructors we will specialize with. It must cover the whole type. let mut split_ctors = split_set.present; - let mut only_report_missing = false; if !split_set.missing.is_empty() { // We need to iterate over a full set of constructors, so we add `Missing` to represent the // missing ones. This is explained under "Constructor Splitting" at the top of this file. split_ctors.push(Constructor::Missing); - // For diagnostic purposes we choose to only report the constructors that are missing. Since - // `Missing` matches only the wildcard rows, it matches fewer rows than any normal - // constructor and is therefore guaranteed to result in more witnesses. So skipping the - // other constructors does not jeopardize correctness. - only_report_missing = true; + } else if !split_set.missing_empty.is_empty() && !place_validity.is_known_valid() { + // The missing empty constructors are reachable if the place can contain invalid data. + split_ctors.push(Constructor::Missing); + } + + // Decide what constructors to report. + let always_report_all = is_top_level && !IntRange::is_integral(pcx.ty); + // Whether we should report "Enum::A and Enum::C are missing" or "_ is missing". + let report_individual_missing_ctors = always_report_all || !all_missing; + // Which constructors are considered missing. We ensure that `!missing_ctors.is_empty() => + // split_ctors.contains(Missing)`. The converse usually holds except in the + // `MaybeInvalidButAllowOmittingArms` backwards-compatibility case. + let mut missing_ctors = split_set.missing; + if !place_validity.allows_omitting_empty_arms() { + missing_ctors.extend(split_set.missing_empty); } let mut ret = WitnessMatrix::empty(); @@ -1246,11 +1281,19 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>( compute_exhaustiveness_and_usefulness(cx, &mut spec_matrix, false) }); - if !only_report_missing || matches!(ctor, Constructor::Missing) { + let counts_for_exhaustiveness = match ctor { + Constructor::Missing => !missing_ctors.is_empty(), + // If there are missing constructors we'll report those instead. Since `Missing` matches + // only the wildcard rows, it matches fewer rows than this constructor, and is therefore + // guaranteed to result in the same or more witnesses. So skipping this does not + // jeopardize correctness. + _ => missing_ctors.is_empty(), + }; + if counts_for_exhaustiveness { // Transform witnesses for `spec_matrix` into witnesses for `matrix`. witnesses.apply_constructor( pcx, - &split_set.missing, + &missing_ctors, &ctor, report_individual_missing_ctors, ); diff --git a/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr b/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr index 9a53b54704e9b..367aba3bdd6e6 100644 --- a/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr +++ b/tests/ui/pattern/usefulness/empty-types.exhaustive_patterns.stderr @@ -31,12 +31,6 @@ LL + _ => todo!(), LL + } | -error: unreachable pattern - --> $DIR/empty-types.rs:62:9 - | -LL | &_ => {} - | ^^ - error: unreachable pattern --> $DIR/empty-types.rs:69:9 | @@ -184,42 +178,6 @@ error: unreachable pattern LL | _ => {} | ^ -error: unreachable pattern - --> $DIR/empty-types.rs:158:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:167:13 - | -LL | Some(_) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:171:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:175:13 - | -LL | _a => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:180:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:185:13 - | -LL | _ => {} - | ^ - error: unreachable pattern --> $DIR/empty-types.rs:204:13 | @@ -250,48 +208,6 @@ error: unreachable pattern LL | _ => {} | ^ -error: unreachable pattern - --> $DIR/empty-types.rs:234:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:239:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:245:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:251:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:256:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:262:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:268:13 - | -LL | _ => {} - | ^ - error: unreachable pattern --> $DIR/empty-types.rs:284:9 | @@ -316,18 +232,6 @@ error: unreachable pattern LL | Err(_) => {} | ^^^^^^ -error: unreachable pattern - --> $DIR/empty-types.rs:296:9 - | -LL | &_ => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:299:9 - | -LL | Uninit { value: _ } => {} - | ^^^^^^^^^^^^^^^^^^^ - error[E0004]: non-exhaustive patterns: type `&[!]` is non-empty --> $DIR/empty-types.rs:323:11 | @@ -342,24 +246,6 @@ LL + _ => todo!(), LL + } | -error: unreachable pattern - --> $DIR/empty-types.rs:331:9 - | -LL | [_] => {} - | ^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:332:9 - | -LL | [_, _, ..] => {} - | ^^^^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:337:9 - | -LL | [_, _, _, ..] => {} - | ^^^^^^^^^^^^^ - error[E0004]: non-exhaustive patterns: `&[]` not covered --> $DIR/empty-types.rs:334:11 | @@ -369,20 +255,9 @@ LL | match slice_never { = note: the matched value is of type `&[!]` help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL | [_, _, _, ..] => {}, &[] => todo!() - | ++++++++++++++++ - -error: unreachable pattern - --> $DIR/empty-types.rs:341:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:345:9 +LL ~ [_, _, _, ..] => {}, +LL + &[] => todo!() | -LL | _x => {} - | ^^ error[E0004]: non-exhaustive patterns: `&[]` not covered --> $DIR/empty-types.rs:347:11 @@ -430,18 +305,6 @@ error: unreachable pattern LL | [_, ..] => {} | ^^^^^^^ -error: unreachable pattern - --> $DIR/empty-types.rs:375:9 - | -LL | &[_, _, _] => {} - | ^^^^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:379:9 - | -LL | &[_x, _, _] => {} - | ^^^^^^^^^^^ - error[E0004]: non-exhaustive patterns: type `[!; 0]` is non-empty --> $DIR/empty-types.rs:383:11 | @@ -500,186 +363,6 @@ error: unreachable pattern LL | _a => {} | ^^ -error: unreachable pattern - --> $DIR/empty-types.rs:436:9 - | -LL | &_ => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:444:9 - | -LL | &_a => {} - | ^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:453:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:458:9 - | -LL | _a => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:463:9 - | -LL | &_ => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:468:9 - | -LL | &_a => {} - | ^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:475:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:479:9 - | -LL | _a => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:485:9 - | -LL | ref _a => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:494:9 - | -LL | Some(_) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:499:9 - | -LL | Some(_a) => {} - | ^^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:504:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:509:9 - | -LL | _a => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:514:14 - | -LL | _a @ Some(_) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:521:9 - | -LL | ref _a => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:526:18 - | -LL | ref _a @ Some(_) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:531:18 - | -LL | ref _a @ Some(_b) => {} - | ^^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:538:9 - | -LL | Ok(_) => {} - | ^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:542:9 - | -LL | Ok(_) => {} - | ^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:544:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:549:9 - | -LL | Ok(_a) => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:553:9 - | -LL | Ok(_a) => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:555:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:559:9 - | -LL | Ok(_a) => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:561:9 - | -LL | Err(_) => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:569:9 - | -LL | (_, _) => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:573:9 - | -LL | (_x, _) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:577:9 - | -LL | (_, _x) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:581:9 - | -LL | (0, _x) => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:583:9 - | -LL | (1.., _) => {} - | ^^^^^^^^ - error: unreachable pattern --> $DIR/empty-types.rs:598:9 | @@ -704,73 +387,7 @@ error: unreachable pattern LL | _x if false => {} | ^^ -error: unreachable pattern - --> $DIR/empty-types.rs:613:9 - | -LL | _ if false => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:615:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:622:9 - | -LL | _a if false => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:624:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:629:9 - | -LL | _a if false => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:634:9 - | -LL | &_a if false => {} - | ^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:641:9 - | -LL | Ok(_x) if false => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:643:9 - | -LL | Ok(_) => {} - | ^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:645:9 - | -LL | Err(_) => {} - | ^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:650:9 - | -LL | (_, _x) if false => {} - | ^^^^^^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:652:9 - | -LL | (_, _) => {} - | ^^^^^^ - -error: aborting due to 113 previous errors +error: aborting due to 49 previous errors Some errors have detailed explanations: E0004, E0005. For more information about an error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-types.normal.stderr b/tests/ui/pattern/usefulness/empty-types.normal.stderr index b066393a61e60..133a95a821ba3 100644 --- a/tests/ui/pattern/usefulness/empty-types.normal.stderr +++ b/tests/ui/pattern/usefulness/empty-types.normal.stderr @@ -234,12 +234,6 @@ LL ~ None => {}, LL + Some(_) => todo!() | -error: unreachable pattern - --> $DIR/empty-types.rs:158:13 - | -LL | _ => {} - | ^ - error[E0004]: non-exhaustive patterns: `Some(_)` not covered --> $DIR/empty-types.rs:161:15 | @@ -258,18 +252,6 @@ LL ~ None => {}, LL + Some(_) => todo!() | -error: unreachable pattern - --> $DIR/empty-types.rs:180:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:185:13 - | -LL | _ => {} - | ^ - error: unreachable pattern --> $DIR/empty-types.rs:204:13 | @@ -300,48 +282,6 @@ error: unreachable pattern LL | _ => {} | ^ -error: unreachable pattern - --> $DIR/empty-types.rs:234:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:239:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:245:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:251:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:256:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:262:13 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:268:13 - | -LL | _ => {} - | ^ - error: unreachable pattern --> $DIR/empty-types.rs:284:9 | @@ -448,8 +388,9 @@ LL | match slice_never { = note: the matched value is of type `&[!]` help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms | -LL | [_, _, _, ..] => {}, &[] | &[_] | &[_, _] => todo!() - | +++++++++++++++++++++++++++++++++ +LL ~ [_, _, _, ..] => {}, +LL + &[] | &[_] | &[_, _] => todo!() + | error[E0004]: non-exhaustive patterns: `&[]` and `&[_, ..]` not covered --> $DIR/empty-types.rs:347:11 @@ -545,24 +486,6 @@ LL ~ &None => {}, LL + &Some(_) => todo!() | -error: unreachable pattern - --> $DIR/empty-types.rs:475:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:479:9 - | -LL | _a => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:485:9 - | -LL | ref _a => {} - | ^^^^^^ - error[E0004]: non-exhaustive patterns: `Some(_)` not covered --> $DIR/empty-types.rs:487:11 | @@ -595,8 +518,9 @@ note: `Result` defined here = note: the matched value is of type `Result` help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL | Ok(_) => {}, Err(_) => todo!() - | +++++++++++++++++++ +LL ~ Ok(_) => {}, +LL + Err(_) => todo!() + | error[E0004]: non-exhaustive patterns: `Err(_)` not covered --> $DIR/empty-types.rs:546:11 @@ -612,8 +536,9 @@ note: `Result` defined here = note: the matched value is of type `Result` help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL | Ok(_a) => {}, Err(_) => todo!() - | +++++++++++++++++++ +LL ~ Ok(_a) => {}, +LL + Err(_) => todo!() + | error[E0004]: non-exhaustive patterns: type `(u32, !)` is non-empty --> $DIR/empty-types.rs:565:11 @@ -653,36 +578,6 @@ error: unreachable pattern LL | _x if false => {} | ^^ -error: unreachable pattern - --> $DIR/empty-types.rs:613:9 - | -LL | _ if false => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:615:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:622:9 - | -LL | _a if false => {} - | ^^ - -error: unreachable pattern - --> $DIR/empty-types.rs:624:9 - | -LL | _ => {} - | ^ - -error: unreachable pattern - --> $DIR/empty-types.rs:629:9 - | -LL | _a if false => {} - | ^^ - error[E0004]: non-exhaustive patterns: `&_` not covered --> $DIR/empty-types.rs:631:11 | @@ -694,8 +589,9 @@ LL | match ref_never { = note: match arms with guards don't count towards exhaustivity help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL | &_a if false => {}, &_ => todo!() - | +++++++++++++++ +LL ~ &_a if false => {}, +LL + &_ => todo!() + | error[E0004]: non-exhaustive patterns: `Some(_)` not covered --> $DIR/empty-types.rs:659:11 @@ -715,7 +611,7 @@ LL ~ None => {}, LL + Some(_) => todo!() | -error: aborting due to 66 previous errors +error: aborting due to 48 previous errors Some errors have detailed explanations: E0004, E0005. For more information about an error, try `rustc --explain E0004`. diff --git a/tests/ui/pattern/usefulness/empty-types.rs b/tests/ui/pattern/usefulness/empty-types.rs index fc422298a3192..1e1d23e446d4c 100644 --- a/tests/ui/pattern/usefulness/empty-types.rs +++ b/tests/ui/pattern/usefulness/empty-types.rs @@ -59,7 +59,7 @@ fn basic(x: NeverBundle) { } match ref_never { // useful, reachable - &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_ => {} } let tuple_half_never: (u32, !) = x.tuple_half_never; @@ -155,7 +155,7 @@ fn void_same_as_never(x: NeverBundle) { let ref_void: &Void = &x.void; match *ref_void {} match *ref_void { - _ => {} //~ ERROR unreachable pattern + _ => {} } let ref_opt_void: &Option = &None; match *ref_opt_void { @@ -164,25 +164,25 @@ fn void_same_as_never(x: NeverBundle) { } match *ref_opt_void { None => {} - Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Some(_) => {} } match *ref_opt_void { None => {} - _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} } match *ref_opt_void { None => {} - _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _a => {} } let union_void = Uninit::::new(); match union_void.value {} match union_void.value { - _ => {} //~ ERROR unreachable pattern + _ => {} } let ptr_void: *const Void = std::ptr::null(); match *ptr_void {} match *ptr_void { - _ => {} //~ ERROR unreachable pattern + _ => {} } } } @@ -231,41 +231,41 @@ fn invalid_scrutinees(x: NeverBundle) { // A pointer may point to a place with an invalid value. match *ptr_never {} match *ptr_never { - _ => {} //~ ERROR unreachable pattern + _ => {} } // A reference may point to a place with an invalid value. match *ref_never {} match *ref_never { - _ => {} //~ ERROR unreachable pattern + _ => {} } // This field access is a dereference. let ref_x: &NeverBundle = &x; match ref_x.never {} match ref_x.never { - _ => {} //~ ERROR unreachable pattern + _ => {} } // This nested field access is a dereference. let nested_ref_x: &NestedNeverBundle = &nested_x; match nested_ref_x.0.never {} match nested_ref_x.0.never { - _ => {} //~ ERROR unreachable pattern + _ => {} } // A cast does not load. match (*ptr_never as Void) {} match (*ptr_never as Void) { - _ => {} //~ ERROR unreachable pattern + _ => {} } // A union field may contain invalid data. let union_never = Uninit::::new(); match union_never.value {} match union_never.value { - _ => {} //~ ERROR unreachable pattern + _ => {} } // Indexing is like a field access. This one accesses behind a reference. let slice_never: &[!] = &[]; match slice_never[0] {} match slice_never[0] { - _ => {} //~ ERROR unreachable pattern + _ => {} } } } @@ -293,10 +293,10 @@ fn nested_validity_tracking(bundle: NeverBundle) { // These should be considered !known_valid and not warn unreachable. match ref_never { - &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_ => {} } match union_never { - Uninit { value: _ } => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Uninit { value: _ } => {} } } @@ -328,21 +328,21 @@ fn arrays_and_slices(x: NeverBundle) { } match slice_never { [] => {} - [_] => {} //[exhaustive_patterns]~ ERROR unreachable pattern - [_, _, ..] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + [_] => {} + [_, _, ..] => {} } match slice_never { //[normal]~^ ERROR `&[]`, `&[_]` and `&[_, _]` not covered //[exhaustive_patterns]~^^ ERROR `&[]` not covered - [_, _, _, ..] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + [_, _, _, ..] => {} } match slice_never { [] => {} - _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} } match slice_never { [] => {} - _x => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _x => {} } match slice_never { //[normal]~^ ERROR `&[]` and `&[_, ..]` not covered @@ -372,11 +372,11 @@ fn arrays_and_slices(x: NeverBundle) { let ref_array_3_never: &[!; 3] = &array_3_never; match ref_array_3_never { // useful, reachable - &[_, _, _] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &[_, _, _] => {} } match ref_array_3_never { // useful, !reachable - &[_x, _, _] => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &[_x, _, _] => {} } let array_0_never: [!; 0] = []; @@ -433,7 +433,7 @@ fn bindings(x: NeverBundle) { } match ref_never { // useful, reachable - &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_ => {} } match ref_never { // useful, reachable @@ -441,7 +441,7 @@ fn bindings(x: NeverBundle) { } match ref_never { // useful, !reachable - &_a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_a => {} } match ref_opt_never { //[normal]~^ ERROR non-exhaustive @@ -450,39 +450,39 @@ fn bindings(x: NeverBundle) { match ref_opt_never { &None => {} // useful, reachable - _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} } match ref_opt_never { &None => {} // useful, reachable - _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _a => {} } match ref_opt_never { &None => {} // useful, reachable - &_ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_ => {} } match ref_opt_never { &None => {} // useful, !reachable - &_a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_a => {} } // On a !known_valid place. match *ref_never {} match *ref_never { // useful, reachable - _ => {} //~ ERROR unreachable pattern + _ => {} } match *ref_never { // useful, !reachable - _a => {} //~ ERROR unreachable pattern + _a => {} } // This is equivalent to `match ref_never { _a => {} }`. In other words, it asserts validity of // `ref_never` but says nothing of the data at `*ref_never`. match *ref_never { // useful, reachable - ref _a => {} //~ ERROR unreachable pattern + ref _a => {} } match *ref_opt_never { //[normal]~^ ERROR non-exhaustive @@ -491,74 +491,74 @@ fn bindings(x: NeverBundle) { match *ref_opt_never { None => {} // useful, reachable - Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Some(_) => {} } match *ref_opt_never { None => {} // useful, !reachable - Some(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Some(_a) => {} } match *ref_opt_never { None => {} // useful, reachable - _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} } match *ref_opt_never { None => {} // useful, !reachable - _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _a => {} } match *ref_opt_never { None => {} // useful, !reachable - _a @ Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _a @ Some(_) => {} } // This is equivalent to `match ref_opt_never { None => {}, _a => {} }`. In other words, it // asserts validity of `ref_opt_never` but says nothing of the data at `*ref_opt_never`. match *ref_opt_never { None => {} // useful, reachable - ref _a => {} //[exhaustive_patterns]~ ERROR unreachable pattern + ref _a => {} } match *ref_opt_never { None => {} // useful, reachable - ref _a @ Some(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + ref _a @ Some(_) => {} } match *ref_opt_never { None => {} // useful, !reachable - ref _a @ Some(_b) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + ref _a @ Some(_b) => {} } let ref_res_never: &Result = &x.result_never; match *ref_res_never { //[normal]~^ ERROR non-exhaustive // useful, reachable - Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_) => {} } match *ref_res_never { // useful, reachable - Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_) => {} // useful, reachable - _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} } match *ref_res_never { //[normal]~^ ERROR non-exhaustive // useful, !reachable - Ok(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_a) => {} } match *ref_res_never { // useful, !reachable - Ok(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_a) => {} // useful, reachable - _ => {} //[exhaustive_patterns]~ ERROR unreachable pattern + _ => {} } match *ref_res_never { // useful, !reachable - Ok(_a) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_a) => {} // useful, reachable - Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Err(_) => {} } let ref_tuple_half_never: &(u32, !) = &x.tuple_half_never; @@ -566,21 +566,21 @@ fn bindings(x: NeverBundle) { //[normal]~^ ERROR non-empty match *ref_tuple_half_never { // useful, reachable - (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (_, _) => {} } match *ref_tuple_half_never { // useful, reachable - (_x, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (_x, _) => {} } match *ref_tuple_half_never { // useful, !reachable - (_, _x) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (_, _x) => {} } match *ref_tuple_half_never { // useful, !reachable - (0, _x) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (0, _x) => {} // useful, reachable - (1.., _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (1.., _) => {} } } @@ -610,46 +610,46 @@ fn guards_and_validity(x: NeverBundle) { // If the pattern under the guard doesn't load, all is normal. match *ref_never { // useful, reachable - _ if false => {} //~ ERROR unreachable pattern + _ if false => {} // useful, reachable - _ => {} //~ ERROR unreachable pattern + _ => {} } // Now the madness commences. The guard caused a load of the value thus asserting validity. So // there's no invalid value for `_` to catch. So the second pattern is unreachable despite the // guard not being taken. match *ref_never { // useful, !reachable - _a if false => {} //~ ERROR unreachable pattern + _a if false => {} // !useful, !reachable - _ => {} //~ ERROR unreachable pattern + _ => {} } // The above still applies to the implicit `_` pattern used for exhaustiveness. match *ref_never { // useful, !reachable - _a if false => {} //~ ERROR unreachable pattern + _a if false => {} } match ref_never { //[normal]~^ ERROR non-exhaustive // useful, !reachable - &_a if false => {} //[exhaustive_patterns]~ ERROR unreachable pattern + &_a if false => {} } // Same but with subpatterns. let ref_result_never: &Result = &x.result_never; match *ref_result_never { // useful, !reachable - Ok(_x) if false => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_x) if false => {} // !useful, !reachable - Ok(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Ok(_) => {} // useful, !reachable - Err(_) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + Err(_) => {} } let ref_tuple_never: &(!, !) = &x.tuple_never; match *ref_tuple_never { // useful, !reachable - (_, _x) if false => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (_, _x) if false => {} // !useful, !reachable - (_, _) => {} //[exhaustive_patterns]~ ERROR unreachable pattern + (_, _) => {} } } diff --git a/tests/ui/pattern/usefulness/slice_of_empty.rs b/tests/ui/pattern/usefulness/slice_of_empty.rs index fe068871195a2..3cbd0eba57fd1 100644 --- a/tests/ui/pattern/usefulness/slice_of_empty.rs +++ b/tests/ui/pattern/usefulness/slice_of_empty.rs @@ -11,12 +11,12 @@ fn foo(nevers: &[!]) { match nevers { &[] => (), - &[_] => (), //~ ERROR unreachable pattern - &[_, _, ..] => (), //~ ERROR unreachable pattern + &[_] => (), + &[_, _, ..] => (), }; match nevers { //~^ ERROR non-exhaustive patterns: `&[]` not covered - &[_] => (), //~ ERROR unreachable pattern + &[_] => (), }; } diff --git a/tests/ui/pattern/usefulness/slice_of_empty.stderr b/tests/ui/pattern/usefulness/slice_of_empty.stderr index 07bb6b3a67d8e..d56360d4cec07 100644 --- a/tests/ui/pattern/usefulness/slice_of_empty.stderr +++ b/tests/ui/pattern/usefulness/slice_of_empty.stderr @@ -1,27 +1,3 @@ -error: unreachable pattern - --> $DIR/slice_of_empty.rs:14:9 - | -LL | &[_] => (), - | ^^^^ - | -note: the lint level is defined here - --> $DIR/slice_of_empty.rs:3:9 - | -LL | #![deny(unreachable_patterns)] - | ^^^^^^^^^^^^^^^^^^^^ - -error: unreachable pattern - --> $DIR/slice_of_empty.rs:15:9 - | -LL | &[_, _, ..] => (), - | ^^^^^^^^^^^ - -error: unreachable pattern - --> $DIR/slice_of_empty.rs:20:9 - | -LL | &[_] => (), - | ^^^^ - error[E0004]: non-exhaustive patterns: `&[]` not covered --> $DIR/slice_of_empty.rs:18:11 | @@ -31,9 +7,10 @@ LL | match nevers { = note: the matched value is of type `&[!]` help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | -LL | &[_] => (), &[] => todo!(), - | ++++++++++++++++ +LL ~ &[_] => (), +LL ~ &[] => todo!(), + | -error: aborting due to 4 previous errors +error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0004`. diff --git a/tests/ui/uninhabited/uninhabited-patterns.rs b/tests/ui/uninhabited/uninhabited-patterns.rs index 43b19e790e2f8..4e90691e5c809 100644 --- a/tests/ui/uninhabited/uninhabited-patterns.rs +++ b/tests/ui/uninhabited/uninhabited-patterns.rs @@ -22,14 +22,14 @@ fn main() { match x { &[] => (), - &[..] => (), //~ ERROR unreachable pattern + &[..] => (), }; let x: Result, &[Result]> = Err(&[]); match x { Ok(box _) => (), //~ ERROR unreachable pattern Err(&[]) => (), - Err(&[..]) => (), //~ ERROR unreachable pattern + Err(&[..]) => (), } let x: Result> = Err(Err(123)); diff --git a/tests/ui/uninhabited/uninhabited-patterns.stderr b/tests/ui/uninhabited/uninhabited-patterns.stderr index 19f34a52bdbe5..a6fda88f03281 100644 --- a/tests/ui/uninhabited/uninhabited-patterns.stderr +++ b/tests/ui/uninhabited/uninhabited-patterns.stderr @@ -1,8 +1,8 @@ error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:25:9 + --> $DIR/uninhabited-patterns.rs:30:9 | -LL | &[..] => (), - | ^^^^^ +LL | Ok(box _) => (), + | ^^^^^^^^^ | note: the lint level is defined here --> $DIR/uninhabited-patterns.rs:4:9 @@ -10,18 +10,6 @@ note: the lint level is defined here LL | #![deny(unreachable_patterns)] | ^^^^^^^^^^^^^^^^^^^^ -error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:30:9 - | -LL | Ok(box _) => (), - | ^^^^^^^^^ - -error: unreachable pattern - --> $DIR/uninhabited-patterns.rs:32:9 - | -LL | Err(&[..]) => (), - | ^^^^^^^^^^ - error: unreachable pattern --> $DIR/uninhabited-patterns.rs:39:9 | @@ -34,5 +22,5 @@ error: unreachable pattern LL | while let Some(_y) = foo() { | ^^^^^^^^ -error: aborting due to 5 previous errors +error: aborting due to 3 previous errors From c3df51a976dfa69f0f1869997fdf79516ba6afab Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sat, 9 Dec 2023 00:50:52 +0100 Subject: [PATCH 7/7] Some types cannot show up as the type of a pattern --- .../rustc_mir_build/src/thir/pattern/deconstruct_pat.rs | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs index e66402a7eb3ba..ef20b0f039b79 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs @@ -1101,13 +1101,12 @@ impl ConstructorSet { | ty::Dynamic(_, _, _) | ty::Closure(_, _) | ty::Coroutine(_, _, _) - | ty::CoroutineWitness(_, _) | ty::Alias(_, _) | ty::Param(_) - | ty::Bound(_, _) - | ty::Placeholder(_) - | ty::Infer(_) | ty::Error(_) => Self::Unlistable, + ty::CoroutineWitness(_, _) | ty::Bound(_, _) | ty::Placeholder(_) | ty::Infer(_) => { + bug!("Encountered unexpected type in `ConstructorSet::for_ty`: {ty:?}") + } } }