4db6a9b82f
In our type inference system, when we "generalize" a type T to become a suitable value for a type variable V, we sometimes wind up creating new inference variables. So, for example, if we are making V be some subtype of `&'X u32`, then we might instantiate V with `&'Y u32`. This generalized type is then related `&'Y u32 <: &'X u32`, resulting in a region constriant `'Y: 'X`. Previously, however, we were making these fresh variables like `'Y` in the "current universe", but they should be created in the universe of V. Moreover, we sometimes cheat in an invariant context and avoid creating fresh variables if we know the result must be equal -- we can only do that when the universes work out.
13 lines
420 B
Plaintext
13 lines
420 B
Plaintext
error[E0308]: mismatched types
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--> $DIR/issue-57843.rs:23:9
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LL | Foo(Box::new(|_| ())); //~ ERROR mismatched types
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| ^^^^^^^^^^^^^^^^ one type is more general than the other
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= note: expected type `std::ops::FnOnce<(&'a bool,)>`
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found type `std::ops::FnOnce<(&bool,)>`
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0308`.
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