Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

trait_sel: resolve vars in host effects #137604

Merged
merged 1 commit into from
Feb 26, 2025
Merged

trait_sel: resolve vars in host effects #137604

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions compiler/rustc_trait_selection/src/traits/effects.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,8 @@ pub fn evaluate_host_effect_obligation<'tcx>(
);
}

let ref obligation = selcx.infcx.resolve_vars_if_possible(obligation.clone());

// Force ambiguity for infer self ty.
if obligation.predicate.self_ty().is_ty_var() {
return Err(EvaluationFailure::Ambiguous);
Expand Down
36 changes: 36 additions & 0 deletions tests/ui/traits/const-traits/unconstrained-var-specialization.rs
View file
Open in desktop
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

On nightly this emits

error[E0283]: type annotations needed: cannot satisfy `Iter: Tr`
  --> src/lib.rs:31:33
   |
31 | impl<A: const Foo, Iter> Tr for Iter
   |                                 ^^^^
   |
note: multiple `impl`s satisfying `Iter: Tr` found
  --> src/lib.rs:24:1
   |
24 | / impl<A: const Foo, Iter> Tr for Iter
25 | |     where
26 | |         Iter: Iterator<Item = A>,
   | |_________________________________^
...
31 | / impl<A: const Foo, Iter> Tr for Iter
32 | |     where
33 | |         Iter: MoreSpecificThanIterator<Item = A>,
   | |_________________________________________________^

Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
//@ check-pass
//@ compile-flags: --crate-type=lib
#![no_std]
#![allow(internal_features)]
#![feature(rustc_attrs, min_specialization, const_trait_impl)]

// In the default impl below, `A` is constrained by the projection predicate, and if the host effect
// predicate for `const Foo` doesn't resolve vars, then specialization will fail.

#[const_trait]
trait Foo {}

pub trait Iterator {
type Item;
}

#[rustc_unsafe_specialization_marker]
pub trait MoreSpecificThanIterator: Iterator {}

pub trait Tr {
fn foo();
}

impl<A: const Foo, Iter> Tr for Iter
where
Iter: Iterator<Item = A>,
{
default fn foo() {}
}

impl<A: const Foo, Iter> Tr for Iter
where
Iter: MoreSpecificThanIterator<Item = A>,
{
fn foo() {}
}
Loading