rust/tests/ui/associated-types/impl-wf-cycle-4.rs

trait Filter {
    type ToMatch;
}

impl<T> Filter for T //~ ERROR overflow evaluating the requirement
where
    T: Fn(Self::ToMatch),
{
}

struct JustFilter<F: Filter> {
    filter: F,
}

fn main() {}
Provide more context on recursive `impl` evaluation overflow When an associated type `Self::Assoc` is part of a `where` clause, we end up unable to evaluate the requirement and emit a E0275. We now point at the associated type if specified in the `impl`. If so, we also suggest using that type instead of `Self::Assoc`. Otherwise, we explain that these are not allowed. ``` error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _` --> $DIR/impl-wf-cycle-1.rs:15:1 \| LL \| / impl<T: Grault> Grault for (T,) LL \| \| LL \| \| where LL \| \| Self::A: Baz, LL \| \| Self::B: Fiz, \| \|_________________^ LL \| { LL \| type A = (); \| ------ associated type `<(T,) as Grault>::A` is specified here \| note: required for `(T,)` to implement `Grault` --> $DIR/impl-wf-cycle-1.rs:15:17 \| LL \| impl<T: Grault> Grault for (T,) \| ^^^^^^ ^^^^ ... LL \| Self::A: Baz, \| --- unsatisfied trait bound introduced here = note: 1 redundant requirement hidden = note: required for `(T,)` to implement `Grault` help: associated type for the current `impl` cannot be restricted in `where` clauses, remove this bound \| LL - Self::A: Baz, LL + , \| ``` ``` error[E0275]: overflow evaluating the requirement `<T as B>::Type == <T as B>::Type` --> $DIR/impl-wf-cycle-3.rs:7:1 \| LL \| / impl<T> B for T LL \| \| where LL \| \| T: A<Self::Type>, \| \|_____________________^ LL \| { LL \| type Type = bool; \| --------- associated type `<T as B>::Type` is specified here \| note: required for `T` to implement `B` --> $DIR/impl-wf-cycle-3.rs:7:9 \| LL \| impl<T> B for T \| ^ ^ LL \| where LL \| T: A<Self::Type>, \| ------------- unsatisfied trait bound introduced here help: replace the associated type with the type specified in this `impl` \| LL \| T: A<bool>, \| ~~~~ ``` ``` error[E0275]: overflow evaluating the requirement `<T as Filter>::ToMatch == <T as Filter>::ToMatch` --> $DIR/impl-wf-cycle-4.rs:5:1 \| LL \| / impl<T> Filter for T LL \| \| where LL \| \| T: Fn(Self::ToMatch), \| \|_________________________^ \| note: required for `T` to implement `Filter` --> $DIR/impl-wf-cycle-4.rs:5:9 \| LL \| impl<T> Filter for T \| ^^^^^^ ^ LL \| where LL \| T: Fn(Self::ToMatch), \| ----------------- unsatisfied trait bound introduced here note: associated types for the current `impl` cannot be restricted in `where` clauses --> $DIR/impl-wf-cycle-4.rs:7:11 \| LL \| T: Fn(Self::ToMatch), \| ^^^^^^^^^^^^^ ``` Fix #116925 2023-12-28 19:09:04 +00:00			`trait Filter {`
			`type ToMatch;`
			`}`

			`impl<T> Filter for T //~ ERROR overflow evaluating the requirement`
			`where`
			`T: Fn(Self::ToMatch),`
			`{`
			`}`

			`struct JustFilter<F: Filter> {`
			`filter: F,`
			`}`

			`fn main() {}`