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add note suggesting that predicate is satisfied but is not const

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This commit is contained in:
Michael Goulet 2022-01-26 19:09:44 -08:00
parent 009c1d0248
commit 1ab97dbc52
9 changed files with 71 additions and 0 deletions
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9
compiler/rustc_middle/src/ty/mod.rs
View File

@ -803,6 +803,10 @@ pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
p
});
}
pub fn is_const(self) -> bool {
self.skip_binder().constness == BoundConstness::ConstIfConst
}
}
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
@ -1388,6 +1392,10 @@ pub fn constness(self) -> hir::Constness {
self.packed.tag().constness
}
pub fn is_const(self) -> bool {
self.packed.tag().constness == hir::Constness::Const
}
/// Construct a trait environment with no where-clauses in scope
/// where the values of all `impl Trait` and other hidden types
/// are revealed. This is suitable for monomorphized, post-typeck
@ -1503,6 +1511,7 @@ pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tc
polarity: ty::ImplPolarity::Positive,
})
}
#[inline]
pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
self.with_constness(BoundConstness::NotConst)

22
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View File

@ -439,6 +439,28 @@ fn report_selection_error(
} else {
err.span_label(span, explanation);
}
if trait_predicate.is_const() && obligation.param_env.is_const() {
let non_const_predicate = trait_ref.without_const();
let non_const_obligation = Obligation {
cause: obligation.cause.clone(),
param_env: obligation.param_env.without_const(),
predicate: non_const_predicate.to_predicate(tcx),
recursion_depth: obligation.recursion_depth,
};
if self.predicate_may_hold(&non_const_obligation) {
err.span_note(
span,
&format!(
"the trait `{}` is implemented for `{}`, \
but that implementation is not `const`",
non_const_predicate.print_modifiers_and_trait_path(),
trait_ref.skip_binder().self_ty(),
),
);
}
}
if let Some((msg, span)) = type_def {
err.span_label(span, &msg);
}

5
src/test/ui/intrinsics/const-eval-select-bad.stderr
View File

@ -7,6 +7,11 @@ LL | const_eval_select((), || {}, || {});
| required by a bound introduced by this call
|
= help: the trait `~const FnOnce<()>` is not implemented for `[closure@$DIR/const-eval-select-bad.rs:6:27: 6:32]`
note: the trait `FnOnce<()>` is implemented for `[closure@$DIR/const-eval-select-bad.rs:6:27: 6:32]`, but that implementation is not `const`
--> $DIR/const-eval-select-bad.rs:6:27
|
LL | const_eval_select((), || {}, || {});
| ^^^^^
= note: wrap the `[closure@$DIR/const-eval-select-bad.rs:6:27: 6:32]` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `const_eval_select`
--> $SRC_DIR/core/src/intrinsics.rs:LL:COL

5
src/test/ui/rfc-2632-const-trait-impl/assoc-type.stderr
View File

@ -5,6 +5,11 @@ LL | type Bar = NonConstAdd;
| ^^^^^^^^^^^ no implementation for `NonConstAdd + NonConstAdd`
|
= help: the trait `~const Add` is not implemented for `NonConstAdd`
note: the trait `Add` is implemented for `NonConstAdd`, but that implementation is not `const`
--> $DIR/assoc-type.rs:18:16
|
LL | type Bar = NonConstAdd;
| ^^^^^^^^^^^
note: required by a bound in `Foo::Bar`
--> $DIR/assoc-type.rs:14:15
|

5
src/test/ui/rfc-2632-const-trait-impl/call-generic-method-nonconst.stderr
View File

@ -7,6 +7,11 @@ LL | pub const EQ: bool = equals_self(&S);
| required by a bound introduced by this call
|
= help: the trait `~const PartialEq` is not implemented for `S`
note: the trait `PartialEq` is implemented for `S`, but that implementation is not `const`
--> $DIR/call-generic-method-nonconst.rs:19:34
|
LL | pub const EQ: bool = equals_self(&S);
| ^^
note: required by a bound in `equals_self`
--> $DIR/call-generic-method-nonconst.rs:12:25
|

5
src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.precise.stderr
View File

@ -28,6 +28,11 @@ LL | const _: () = check($exp);
LL | ConstImplWithDropGlue(NonTrivialDrop),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ within `ConstImplWithDropGlue`, the trait `~const Drop` is not implemented for `NonTrivialDrop`
|
note: the trait `Drop` is implemented for `NonTrivialDrop`, but that implementation is not `const`
--> $DIR/const-drop-fail.rs:46:5
|
LL | ConstImplWithDropGlue(NonTrivialDrop),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required because it appears within the type `ConstImplWithDropGlue`
--> $DIR/const-drop-fail.rs:17:8
|

5
src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.stock.stderr
View File

@ -28,6 +28,11 @@ LL | const _: () = check($exp);
LL | ConstImplWithDropGlue(NonTrivialDrop),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ within `ConstImplWithDropGlue`, the trait `~const Drop` is not implemented for `NonTrivialDrop`
|
note: the trait `Drop` is implemented for `NonTrivialDrop`, but that implementation is not `const`
--> $DIR/const-drop-fail.rs:46:5
|
LL | ConstImplWithDropGlue(NonTrivialDrop),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required because it appears within the type `ConstImplWithDropGlue`
--> $DIR/const-drop-fail.rs:17:8
|

5
src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-body-checking.stderr
View File

@ -4,6 +4,11 @@ error[E0277]: the trait bound `(): ~const Tr` is not satisfied
LL | foo::<()>();
| ^^ the trait `~const Tr` is not implemented for `()`
|
note: the trait `Tr` is implemented for `()`, but that implementation is not `const`
--> $DIR/default-method-body-is-const-body-checking.rs:12:15
|
LL | foo::<()>();
| ^^
note: required by a bound in `foo`
--> $DIR/default-method-body-is-const-body-checking.rs:7:28
|

10
src/test/ui/rfc-2632-const-trait-impl/trait-where-clause.stderr
View File

@ -4,6 +4,11 @@ error[E0277]: the trait bound `T: ~const Bar` is not satisfied
LL | T::b();
| ^^^^ the trait `~const Bar` is not implemented for `T`
|
note: the trait `Bar` is implemented for `T`, but that implementation is not `const`
--> $DIR/trait-where-clause.rs:14:5
|
LL | T::b();
| ^^^^
note: required by a bound in `Foo::b`
--> $DIR/trait-where-clause.rs:8:24
|
@ -20,6 +25,11 @@ error[E0277]: the trait bound `T: ~const Bar` is not satisfied
LL | T::c::<T>();
| ^^^^^^^^^ the trait `~const Bar` is not implemented for `T`
|
note: the trait `Bar` is implemented for `T`, but that implementation is not `const`
--> $DIR/trait-where-clause.rs:16:5
|
LL | T::c::<T>();
| ^^^^^^^^^
note: required by a bound in `Foo::c`
--> $DIR/trait-where-clause.rs:9:13
|