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Revert "Unify tcx.constness and param env constness checks" #103284

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Oct 26, 2022
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Revert "Unify tcx.constness and param env constness checks" #103284

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ab36a2f
Revert "Unify tcx.constness and param env constness checks"
compiler-errors Oct 19, 2022
43f2c37
Note discrepancies in constness calculation
compiler-errors Oct 19, 2022
751ac6c
Bless test
compiler-errors Oct 20, 2022
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72 changes: 16 additions & 56 deletions compiler/rustc_const_eval/src/const_eval/fn_queries.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,10 +25,12 @@ pub fn is_parent_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
/// report whether said intrinsic has a `rustc_const_{un,}stable` attribute. Otherwise, return
/// `Constness::NotConst`.
fn constness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Constness {
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
match tcx.hir().get(hir_id) {
hir::Node::Ctor(_) => hir::Constness::Const,
let def_id = def_id.expect_local();
let node = tcx.hir().get_by_def_id(def_id);

match node {
hir::Node::Ctor(_) => hir::Constness::Const,
hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.constness,
hir::Node::ForeignItem(hir::ForeignItem { kind: hir::ForeignItemKind::Fn(..), .. }) => {
// Intrinsics use `rustc_const_{un,}stable` attributes to indicate constness. All other
// foreign items cannot be evaluated at compile-time.
Expand All @@ -39,62 +41,20 @@ fn constness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Constness {
};
if is_const { hir::Constness::Const } else { hir::Constness::NotConst }
}
_ => {
if let Some(fn_kind) = node.fn_kind() {
if fn_kind.constness() == hir::Constness::Const {
return hir::Constness::Const;
}

hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
if tcx.is_const_default_method(def_id) =>
{
hir::Constness::Const
}

hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
| hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Const(..), .. })
| hir::Node::AnonConst(_)
| hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
| hir::Node::ImplItem(hir::ImplItem {
kind:
hir::ImplItemKind::Fn(
hir::FnSig {
header: hir::FnHeader { constness: hir::Constness::Const, .. },
..
},
..,
),
..
}) => hir::Constness::Const,

hir::Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Type(..) | hir::ImplItemKind::Fn(..),
..
}) => {
let parent_hir_id = tcx.hir().get_parent_node(hir_id);
match tcx.hir().get(parent_hir_id) {
hir::Node::Item(hir::Item {
kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
..
}) => *constness,
_ => span_bug!(
tcx.def_span(parent_hir_id.owner),
"impl item's parent node is not an impl",
),
// If the function itself is not annotated with `const`, it may still be a `const fn`
// if it resides in a const trait impl.
let is_const = is_parent_const_impl_raw(tcx, def_id);
if is_const { hir::Constness::Const } else { hir::Constness::NotConst }
} else {
hir::Constness::NotConst
}
}

hir::Node::Item(hir::Item {
kind: hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
..
})
| hir::Node::TraitItem(hir::TraitItem {
kind:
hir::TraitItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
..
})
| hir::Node::Item(hir::Item {
kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
..
}) => *constness,

_ => hir::Constness::NotConst,
}
}

Expand Down
56 changes: 15 additions & 41 deletions compiler/rustc_metadata/src/rmeta/encoder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1059,43 +1059,6 @@ fn should_encode_const(def_kind: DefKind) -> bool {
}
}

fn should_encode_constness(def_kind: DefKind) -> bool {
match def_kind {
DefKind::Struct
| DefKind::Union
| DefKind::Enum
| DefKind::Trait
| DefKind::AssocTy
| DefKind::Fn
| DefKind::Const
| DefKind::Static(..)
| DefKind::Ctor(..)
| DefKind::AssocFn
| DefKind::AssocConst
| DefKind::AnonConst
| DefKind::InlineConst
| DefKind::OpaqueTy
| DefKind::ImplTraitPlaceholder
| DefKind::Impl
| DefKind::Closure
| DefKind::Generator
| DefKind::TyAlias => true,
DefKind::Variant
| DefKind::TraitAlias
| DefKind::ForeignTy
| DefKind::Field
| DefKind::TyParam
| DefKind::Mod
| DefKind::ForeignMod
| DefKind::ConstParam
| DefKind::Macro(..)
| DefKind::Use
| DefKind::LifetimeParam
| DefKind::GlobalAsm
| DefKind::ExternCrate => false,
}
}

fn should_encode_trait_impl_trait_tys<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
if tcx.def_kind(def_id) != DefKind::AssocFn {
return false;
Expand Down Expand Up @@ -1202,9 +1165,6 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
{
record!(self.tables.trait_impl_trait_tys[def_id] <- table);
}
if should_encode_constness(def_kind) {
self.tables.constness.set(def_id.index, tcx.constness(def_id));
}
}
let inherent_impls = tcx.crate_inherent_impls(());
for (def_id, implementations) in inherent_impls.inherent_impls.iter() {
Expand Down Expand Up @@ -1232,6 +1192,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
};

record!(self.tables.variant_data[def_id] <- data);
self.tables.constness.set(def_id.index, hir::Constness::Const);
record_array!(self.tables.children[def_id] <- variant.fields.iter().map(|f| {
assert!(f.did.is_local());
f.did.index
Expand Down Expand Up @@ -1259,6 +1220,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
};

record!(self.tables.variant_data[def_id] <- data);
self.tables.constness.set(def_id.index, hir::Constness::Const);
if variant.ctor_kind == CtorKind::Fn {
record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
}
Expand Down Expand Up @@ -1322,6 +1284,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {

record!(self.tables.repr_options[def_id] <- adt_def.repr());
record!(self.tables.variant_data[def_id] <- data);
self.tables.constness.set(def_id.index, hir::Constness::Const);
if variant.ctor_kind == CtorKind::Fn {
record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
}
Expand Down Expand Up @@ -1357,6 +1320,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
}
};
self.tables.asyncness.set(def_id.index, m_sig.header.asyncness);
self.tables.constness.set(def_id.index, hir::Constness::NotConst);
}
ty::AssocKind::Type => {
self.encode_explicit_item_bounds(def_id);
Expand All @@ -1381,6 +1345,13 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
let hir::ImplItemKind::Fn(ref sig, body) = ast_item.kind else { bug!() };
self.tables.asyncness.set(def_id.index, sig.header.asyncness);
record_array!(self.tables.fn_arg_names[def_id] <- self.tcx.hir().body_param_names(body));
// Can be inside `impl const Trait`, so using sig.header.constness is not reliable
let constness = if self.tcx.is_const_fn_raw(def_id) {
hir::Constness::Const
} else {
hir::Constness::NotConst
};
self.tables.constness.set(def_id.index, constness);
}
ty::AssocKind::Const | ty::AssocKind::Type => {}
}
Expand Down Expand Up @@ -1503,6 +1474,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
hir::ItemKind::Fn(ref sig, .., body) => {
self.tables.asyncness.set(def_id.index, sig.header.asyncness);
record_array!(self.tables.fn_arg_names[def_id] <- self.tcx.hir().body_param_names(body));
self.tables.constness.set(def_id.index, sig.header.constness);
}
hir::ItemKind::Macro(ref macro_def, _) => {
if macro_def.macro_rules {
Expand All @@ -1523,6 +1495,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
hir::ItemKind::Struct(ref struct_def, _) => {
let adt_def = self.tcx.adt_def(def_id);
record!(self.tables.repr_options[def_id] <- adt_def.repr());
self.tables.constness.set(def_id.index, hir::Constness::Const);

// Encode def_ids for each field and method
// for methods, write all the stuff get_trait_method
Expand Down Expand Up @@ -1551,8 +1524,9 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
is_non_exhaustive: variant.is_field_list_non_exhaustive(),
});
}
hir::ItemKind::Impl(hir::Impl { defaultness, .. }) => {
hir::ItemKind::Impl(hir::Impl { defaultness, constness, .. }) => {
self.tables.impl_defaultness.set(def_id.index, *defaultness);
self.tables.constness.set(def_id.index, *constness);

let trait_ref = self.tcx.impl_trait_ref(def_id);
if let Some(trait_ref) = trait_ref {
Expand Down
74 changes: 73 additions & 1 deletion compiler/rustc_ty_utils/src/ty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -137,10 +137,82 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
let local_did = def_id.as_local();
let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));

// FIXME(consts): This is not exactly in line with the constness query.
let constness = match hir_id {
Some(hir_id) => match tcx.hir().get(hir_id) {
hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
if tcx.is_const_default_method(def_id) =>
{
hir::Constness::Const
}

hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
| hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Const(..), ..
})
| hir::Node::AnonConst(_)
| hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
| hir::Node::ImplItem(hir::ImplItem {
kind:
hir::ImplItemKind::Fn(
hir::FnSig {
header: hir::FnHeader { constness: hir::Constness::Const, .. },
..
},
..,
),
..
}) => hir::Constness::Const,

hir::Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Type(..) | hir::ImplItemKind::Fn(..),
..
}) => {
let parent_hir_id = tcx.hir().get_parent_node(hir_id);
match tcx.hir().get(parent_hir_id) {
hir::Node::Item(hir::Item {
kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
..
}) => *constness,
_ => span_bug!(
tcx.def_span(parent_hir_id.owner),
"impl item's parent node is not an impl",
),
}
}

hir::Node::Item(hir::Item {
kind:
hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
..
})
| hir::Node::TraitItem(hir::TraitItem {
kind:
hir::TraitItemKind::Fn(
hir::FnSig { header: hir::FnHeader { constness, .. }, .. },
..,
),
..
})
| hir::Node::Item(hir::Item {
kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
..
}) => *constness,

_ => hir::Constness::NotConst,
},
// FIXME(consts): It's suspicious that a param-env for a foreign item
// will always have NotConst param-env, though we don't typically use
// that param-env for anything meaningful right now, so it's likely
// not an issue.
None => hir::Constness::NotConst,
};

let unnormalized_env = ty::ParamEnv::new(
tcx.intern_predicates(&predicates),
traits::Reveal::UserFacing,
tcx.constness(def_id),
constness,
);

let body_id =
Expand Down
3 changes: 2 additions & 1 deletion src/test/ui/rfc-2632-const-trait-impl/issue-102985.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,8 @@ struct Bug {
inner: [(); match || 1 {
n => n(),
//~^ ERROR the trait bound
//~| ERROR cannot call non-const fn `Bug::inner::{constant#0}::{closure#0}` in constants
//~| ERROR the trait bound
//~| ERROR cannot call non-const closure in constants
}],
}

Expand Down
19 changes: 17 additions & 2 deletions src/test/ui/rfc-2632-const-trait-impl/issue-102985.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -12,15 +12,30 @@ LL | n => n(),
| ^^^
= note: wrap the `[closure@$DIR/issue-102985.rs:4:23: 4:25]` in a closure with no arguments: `|| { /* code */ }`

error[E0015]: cannot call non-const fn `Bug::inner::{constant#0}::{closure#0}` in constants
error[E0277]: the trait bound `[closure@$DIR/issue-102985.rs:4:23: 4:25]: ~const Fn<()>` is not satisfied
--> $DIR/issue-102985.rs:5:14
|
LL | n => n(),
| ^^^ expected an `Fn<()>` closure, found `[closure@$DIR/issue-102985.rs:4:23: 4:25]`
|
= help: the trait `~const Fn<()>` is not implemented for closure `[closure@$DIR/issue-102985.rs:4:23: 4:25]`
note: the trait `Fn<()>` is implemented for `[closure@$DIR/issue-102985.rs:4:23: 4:25]`, but that implementation is not `const`
--> $DIR/issue-102985.rs:5:14
|
LL | n => n(),
| ^^^
= note: wrap the `[closure@$DIR/issue-102985.rs:4:23: 4:25]` in a closure with no arguments: `|| { /* code */ }`

error[E0015]: cannot call non-const closure in constants
--> $DIR/issue-102985.rs:5:14
|
LL | n => n(),
| ^^^
|
= note: closures need an RFC before allowed to be called in constants
= note: calls in constants are limited to constant functions, tuple structs and tuple variants

error: aborting due to 2 previous errors
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0015, E0277.
For more information about an error, try `rustc --explain E0015`.