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Rollup merge of #119540 - fmease:no-effect-args-inside-dyn-trait, r=compiler-errors

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Don't synthesize host effect args inside trait object types

While we were indeed emitting an error for `~const` & `const` trait bounds in trait object types, we were still synthesizing host effect args for them.

Since we don't record the original trait bound modifiers for dyn-Trait in `hir::TyKind::TraitObject` (unlike we do for let's say impl-Trait, `hir::TyKind::OpaqueTy`), AstConv just assumes `ty::BoundConstness::NotConst` in `conv_object_ty_poly_trait_ref` which given `<host> dyn ~const NonConstTrait` resulted in us not realizing that `~const` was used on a non-const trait which lead to a failed assertion in the end.

Instead of updating `hir::TyKind::TraitObject` to track this kind of information, just strip the user-provided constness (similar to #119505).

Fixes #119524.
This commit is contained in:
Matthias Krüger 2024-01-04 08:33:26 +01:00 • committed by GitHub
commit f4335a419f
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3 changed files with 47 additions and 15 deletions
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28
compiler/rustc_ast_lowering/src/lib.rs
View file

@ -1434,19 +1434,21 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| { let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
let bounds = let bounds =
this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| match bound { this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| match bound {
GenericBound::Trait( // We can safely ignore constness here since AST validation
ty, // takes care of rejecting invalid modifier combinations and
TraitBoundModifiers { // const trait bounds in trait object types.
polarity: BoundPolarity::Positive | BoundPolarity::Negative(_), GenericBound::Trait(ty, modifiers) => match modifiers.polarity {
constness, BoundPolarity::Positive | BoundPolarity::Negative(_) => {
}, Some(this.lower_poly_trait_ref(
) => Some(this.lower_poly_trait_ref(ty, itctx, *constness)), ty,
// We can safely ignore constness here, since AST validation itctx,
// will take care of invalid modifier combinations. // Still, don't pass along the constness here; we don't want to
GenericBound::Trait( // synthesize any host effect args, it'd only cause problems.
_, ast::BoundConstness::Never,
TraitBoundModifiers { polarity: BoundPolarity::Maybe(_), .. }, ))
) => None, }
BoundPolarity::Maybe(_) => None,
},
GenericBound::Outlives(lifetime) => { GenericBound::Outlives(lifetime) => {
if lifetime_bound.is_none() { if lifetime_bound.is_none() {
lifetime_bound = Some(this.lower_lifetime(lifetime)); lifetime_bound = Some(this.lower_lifetime(lifetime));

10
tests/ui/rfcs/rfc-2632-const-trait-impl/const-trait-bounds-trait-objects.rs
View file

@ -1,4 +1,4 @@
#![feature(const_trait_impl)] #![feature(const_trait_impl, effects)]
// edition: 2021 // edition: 2021
#[const_trait] #[const_trait]
@ -6,4 +6,12 @@ trait Trait {}
fn main() { fn main() {
let _: &dyn const Trait; //~ ERROR const trait bounds are not allowed in trait object types let _: &dyn const Trait; //~ ERROR const trait bounds are not allowed in trait object types
let _: &dyn ~const Trait; //~ ERROR `~const` is not allowed here
} }
// Regression test for issue #119525.
trait NonConst {}
const fn handle(_: &dyn const NonConst) {}
//~^ ERROR const trait bounds are not allowed in trait object types
const fn take(_: &dyn ~const NonConst) {}
//~^ ERROR `~const` is not allowed here

24
tests/ui/rfcs/rfc-2632-const-trait-impl/const-trait-bounds-trait-objects.stderr
View file

@ -4,5 +4,27 @@ error: const trait bounds are not allowed in trait object types
LL | let _: &dyn const Trait; LL | let _: &dyn const Trait;
| ^^^^^^^^^^^ | ^^^^^^^^^^^
error: aborting due to 1 previous error error: `~const` is not allowed here
--> $DIR/const-trait-bounds-trait-objects.rs:9:17
|
LL | let _: &dyn ~const Trait;
| ^^^^^^
|
= note: trait objects cannot have `~const` trait bounds
error: const trait bounds are not allowed in trait object types
--> $DIR/const-trait-bounds-trait-objects.rs:14:25
|
LL | const fn handle(_: &dyn const NonConst) {}
| ^^^^^^^^^^^^^^
error: `~const` is not allowed here
--> $DIR/const-trait-bounds-trait-objects.rs:16:23
|
LL | const fn take(_: &dyn ~const NonConst) {}
| ^^^^^^
|
= note: trait objects cannot have `~const` trait bounds
error: aborting due to 4 previous errors