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`nominal_obligations` calls `predicates_of` on a `Sized` obligation, effectively elaborating the trait and making the well-formedness checking machinery do a bunch of extra work checking a `MetaSized` obligation is well-formed, but given that both `Sized` and `MetaSized` are built-ins, if `Sized` is otherwise well-formed, so `MetaSized` will be.
25 lines
664 B
Rust
25 lines
664 B
Rust
//@ revisions: current next
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//@ ignore-compare-mode-next-solver (explicit revisions)
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//@[next] compile-flags: -Znext-solver
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// Exercises change in <https://github.com/rust-lang/rust/pull/138176>.
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struct MyType<'a, T: ?Sized>(&'a (), T);
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fn is_sized<T>() {}
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fn foo<'a, T: ?Sized>()
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where
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(MyType<'a, T>,): Sized,
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MyType<'static, T>: Sized,
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{
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// Preferring the builtin `Sized` impl of tuples
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// requires proving `MyType<'a, T>: Sized` which
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// can only be proven by using the where-clause,
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// adding an unnecessary `'static` constraint.
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is_sized::<(MyType<'a, T>,)>();
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//~^ ERROR lifetime may not live long enough
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}
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fn main() {}
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