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Correct comment on privately uninhabited pattern. #111951

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May 26, 2023
Merged

Correct comment on privately uninhabited pattern. #111951

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1895292
Correct comment on privately uninhabited pattern.
cjgillot May 25, 2023
320f6f4
Add inter-crate test.
cjgillot May 25, 2023
ee27c49
Add NOTE annotations.
cjgillot May 25, 2023
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4 changes: 2 additions & 2 deletions compiler/rustc_mir_build/src/thir/pattern/check_match.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -479,8 +479,8 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
AdtDefinedHere { adt_def_span, ty, variants }
};

// Emit an extra note if the first uncovered witness is
// visibly uninhabited anywhere in the current crate.
// Emit an extra note if the first uncovered witness would be uninhabited
// if we disregard visibility.
let witness_1_is_privately_uninhabited =
if cx.tcx.features().exhaustive_patterns
&& let Some(witness_1) = witnesses.get(0)
Expand Down
56 changes: 36 additions & 20 deletions tests/ui/pattern/usefulness/empty-match.exhaustive_patterns.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -28,20 +28,35 @@ error: unreachable pattern
LL | _ if false => {},
| ^

error[E0005]: refutable pattern in local binding
--> $DIR/empty-match.rs:55:9
|
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<SecretlyUninhabitedForeignStruct>`
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:57:9
--> $DIR/empty-match.rs:61:9
|
LL | _ => {},
| ^

error: unreachable pattern
--> $DIR/empty-match.rs:60:9
--> $DIR/empty-match.rs:64:9
|
LL | _ if false => {},
| ^

error[E0004]: non-exhaustive patterns: type `u8` is non-empty
--> $DIR/empty-match.rs:78:20
--> $DIR/empty-match.rs:82:20
|
LL | match_no_arms!(0u8);
| ^^^
Expand All @@ -50,7 +65,7 @@ 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:79:20
--> $DIR/empty-match.rs:83:20
|
LL | match_no_arms!(NonEmptyStruct1);
| ^^^^^^^^^^^^^^^
Expand All @@ -64,7 +79,7 @@ LL | struct 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:80:20
--> $DIR/empty-match.rs:84:20
|
LL | match_no_arms!(NonEmptyStruct2(true));
| ^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -78,7 +93,7 @@ LL | struct NonEmptyStruct2(bool);
= 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:81:20
--> $DIR/empty-match.rs:85:20
|
LL | match_no_arms!((NonEmptyUnion1 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -92,7 +107,7 @@ LL | union 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:82:20
--> $DIR/empty-match.rs:86:20
|
LL | match_no_arms!((NonEmptyUnion2 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -106,7 +121,7 @@ LL | union 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:83:20
--> $DIR/empty-match.rs:87:20
|
LL | match_no_arms!(NonEmptyEnum1::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered
Expand All @@ -122,7 +137,7 @@ LL | Foo(bool),
= 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:84:20
--> $DIR/empty-match.rs:88:20
|
LL | match_no_arms!(NonEmptyEnum2::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered
Expand All @@ -140,7 +155,7 @@ LL | Bar,
= 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:85:20
--> $DIR/empty-match.rs:89:20
|
LL | match_no_arms!(NonEmptyEnum5::V1);
| ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered
Expand All @@ -154,7 +169,7 @@ LL | enum 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:87:24
--> $DIR/empty-match.rs:91:24
|
LL | match_guarded_arm!(0u8);
| ^^^ pattern `_` not covered
Expand All @@ -167,7 +182,7 @@ LL + _ => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyStruct1` not covered
--> $DIR/empty-match.rs:88:24
--> $DIR/empty-match.rs:92:24
|
LL | match_guarded_arm!(NonEmptyStruct1);
| ^^^^^^^^^^^^^^^ pattern `NonEmptyStruct1` not covered
Expand All @@ -185,7 +200,7 @@ LL + NonEmptyStruct1 => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyStruct2(_)` not covered
--> $DIR/empty-match.rs:89:24
--> $DIR/empty-match.rs:93:24
|
LL | match_guarded_arm!(NonEmptyStruct2(true));
| ^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyStruct2(_)` not covered
Expand All @@ -203,7 +218,7 @@ LL + NonEmptyStruct2(_) => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyUnion1 { .. }` not covered
--> $DIR/empty-match.rs:90:24
--> $DIR/empty-match.rs:94:24
|
LL | match_guarded_arm!((NonEmptyUnion1 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion1 { .. }` not covered
Expand All @@ -221,7 +236,7 @@ LL + NonEmptyUnion1 { .. } => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyUnion2 { .. }` not covered
--> $DIR/empty-match.rs:91:24
--> $DIR/empty-match.rs:95:24
|
LL | match_guarded_arm!((NonEmptyUnion2 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion2 { .. }` not covered
Expand All @@ -239,7 +254,7 @@ LL + NonEmptyUnion2 { .. } => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyEnum1::Foo(_)` not covered
--> $DIR/empty-match.rs:92:24
--> $DIR/empty-match.rs:96:24
|
LL | match_guarded_arm!(NonEmptyEnum1::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered
Expand All @@ -259,7 +274,7 @@ LL + NonEmptyEnum1::Foo(_) => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered
--> $DIR/empty-match.rs:93:24
--> $DIR/empty-match.rs:97:24
|
LL | match_guarded_arm!(NonEmptyEnum2::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered
Expand All @@ -281,7 +296,7 @@ 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:94:24
--> $DIR/empty-match.rs:98:24
|
LL | match_guarded_arm!(NonEmptyEnum5::V1);
| ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered
Expand All @@ -298,6 +313,7 @@ LL ~ _ if false => {},
LL + _ => todo!()
|

error: aborting due to 22 previous errors
error: aborting due to 23 previous errors

For more information about this error, try `rustc --explain E0004`.
Some errors have detailed explanations: E0004, E0005.
For more information about an error, try `rustc --explain E0004`.
55 changes: 35 additions & 20 deletions tests/ui/pattern/usefulness/empty-match.normal.stderr
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,20 +28,34 @@ error: unreachable pattern
LL | _ if false => {},
| ^

error[E0005]: refutable pattern in local binding
--> $DIR/empty-match.rs:55:9
|
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<SecretlyUninhabitedForeignStruct>`
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:57:9
--> $DIR/empty-match.rs:61:9
|
LL | _ => {},
| ^

error: unreachable pattern
--> $DIR/empty-match.rs:60:9
--> $DIR/empty-match.rs:64:9
|
LL | _ if false => {},
| ^

error[E0004]: non-exhaustive patterns: type `u8` is non-empty
--> $DIR/empty-match.rs:78:20
--> $DIR/empty-match.rs:82:20
|
LL | match_no_arms!(0u8);
| ^^^
Expand All @@ -50,7 +64,7 @@ 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:79:20
--> $DIR/empty-match.rs:83:20
|
LL | match_no_arms!(NonEmptyStruct1);
| ^^^^^^^^^^^^^^^
Expand All @@ -64,7 +78,7 @@ LL | struct 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:80:20
--> $DIR/empty-match.rs:84:20
|
LL | match_no_arms!(NonEmptyStruct2(true));
| ^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -78,7 +92,7 @@ LL | struct NonEmptyStruct2(bool);
= 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:81:20
--> $DIR/empty-match.rs:85:20
|
LL | match_no_arms!((NonEmptyUnion1 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -92,7 +106,7 @@ LL | union 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:82:20
--> $DIR/empty-match.rs:86:20
|
LL | match_no_arms!((NonEmptyUnion2 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -106,7 +120,7 @@ LL | union 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:83:20
--> $DIR/empty-match.rs:87:20
|
LL | match_no_arms!(NonEmptyEnum1::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered
Expand All @@ -122,7 +136,7 @@ LL | Foo(bool),
= 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:84:20
--> $DIR/empty-match.rs:88:20
|
LL | match_no_arms!(NonEmptyEnum2::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered
Expand All @@ -140,7 +154,7 @@ LL | Bar,
= 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:85:20
--> $DIR/empty-match.rs:89:20
|
LL | match_no_arms!(NonEmptyEnum5::V1);
| ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered
Expand All @@ -154,7 +168,7 @@ LL | enum 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:87:24
--> $DIR/empty-match.rs:91:24
|
LL | match_guarded_arm!(0u8);
| ^^^ pattern `_` not covered
Expand All @@ -167,7 +181,7 @@ LL + _ => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyStruct1` not covered
--> $DIR/empty-match.rs:88:24
--> $DIR/empty-match.rs:92:24
|
LL | match_guarded_arm!(NonEmptyStruct1);
| ^^^^^^^^^^^^^^^ pattern `NonEmptyStruct1` not covered
Expand All @@ -185,7 +199,7 @@ LL + NonEmptyStruct1 => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyStruct2(_)` not covered
--> $DIR/empty-match.rs:89:24
--> $DIR/empty-match.rs:93:24
|
LL | match_guarded_arm!(NonEmptyStruct2(true));
| ^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyStruct2(_)` not covered
Expand All @@ -203,7 +217,7 @@ LL + NonEmptyStruct2(_) => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyUnion1 { .. }` not covered
--> $DIR/empty-match.rs:90:24
--> $DIR/empty-match.rs:94:24
|
LL | match_guarded_arm!((NonEmptyUnion1 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion1 { .. }` not covered
Expand All @@ -221,7 +235,7 @@ LL + NonEmptyUnion1 { .. } => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyUnion2 { .. }` not covered
--> $DIR/empty-match.rs:91:24
--> $DIR/empty-match.rs:95:24
|
LL | match_guarded_arm!((NonEmptyUnion2 { foo: () }));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyUnion2 { .. }` not covered
Expand All @@ -239,7 +253,7 @@ LL + NonEmptyUnion2 { .. } => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyEnum1::Foo(_)` not covered
--> $DIR/empty-match.rs:92:24
--> $DIR/empty-match.rs:96:24
|
LL | match_guarded_arm!(NonEmptyEnum1::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ pattern `NonEmptyEnum1::Foo(_)` not covered
Expand All @@ -259,7 +273,7 @@ LL + NonEmptyEnum1::Foo(_) => todo!()
|

error[E0004]: non-exhaustive patterns: `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered
--> $DIR/empty-match.rs:93:24
--> $DIR/empty-match.rs:97:24
|
LL | match_guarded_arm!(NonEmptyEnum2::Foo(true));
| ^^^^^^^^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum2::Foo(_)` and `NonEmptyEnum2::Bar` not covered
Expand All @@ -281,7 +295,7 @@ 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:94:24
--> $DIR/empty-match.rs:98:24
|
LL | match_guarded_arm!(NonEmptyEnum5::V1);
| ^^^^^^^^^^^^^^^^^ patterns `NonEmptyEnum5::V1`, `NonEmptyEnum5::V2`, `NonEmptyEnum5::V3` and 2 more not covered
Expand All @@ -298,6 +312,7 @@ LL ~ _ if false => {},
LL + _ => todo!()
|

error: aborting due to 22 previous errors
error: aborting due to 23 previous errors

For more information about this error, try `rustc --explain E0004`.
Some errors have detailed explanations: E0004, E0005.
For more information about an error, try `rustc --explain E0004`.
4 changes: 4 additions & 0 deletions tests/ui/pattern/usefulness/empty-match.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,10 @@ fn empty_foreign_enum(x: empty::EmptyForeignEnum) {
}
}

fn empty_foreign_enum_private(x: Option<empty::SecretlyUninhabitedForeignStruct>) {
let None = x; //~ ERROR refutable pattern in local binding
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Could you add the expected notes here too?

}

fn never(x: !) {
match x {} // ok
match x {
Expand Down