40 lines
1022 B
Rust
40 lines
1022 B
Rust
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// check-pass
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// compile-flags: -Ztrait-solver=next
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trait Mirror {
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type Item;
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}
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struct Wrapper<T>(T);
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impl<T> Mirror for Wrapper<T> {
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type Item = T;
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}
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fn mirror<T>()
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where
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Wrapper<T>: Mirror<Item = i32>,
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{
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}
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fn main() {
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mirror::<_ /* ?0 */>();
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// Solving `<Wrapper<?0> as Mirror>::Item = i32`
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// First, we replace the term with a fresh infer var:
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// `<Wrapper<?0> as Mirror>::Item = ?1`
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// We select the impl candidate on line #6, which leads us to learn that
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// `?0 == ?1`.
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// That should be reflected in our canonical response, which should have
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// `^0 = ^0, ^1 = ^0`
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// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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// !! We used to return a totally unconstrained response here :< !!
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// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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// Then, during the "equate term" part of the projection solving, we
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// instantiate the response from the unconstrained projection predicate,
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// and equate `?0 == i32`.
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}
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