mirror of https://github.com/rust-lang/rust
29 lines
958 B
Rust
29 lines
958 B
Rust
//@ check-pass
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//@ aux-build:trait-with-const-param.rs
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extern crate trait_with_const_param;
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use trait_with_const_param::*;
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// Trivial case, const param after local type.
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struct Local1;
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impl<const N: usize, T> Trait<N, T> for Local1 {}
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// Concrete consts behave the same as foreign types,
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// so this also trivially works.
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impl Trait<3, Local1> for i32 {}
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// This case isn't as trivial as we would forbid type
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// parameters here, we do allow const parameters though.
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//
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// The reason that type parameters are forbidden for
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// `impl<T> Trait<T, LocalInA> for i32 {}` is that another
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// downstream crate can add `impl<T> Trait<LocalInB, T> for i32`.
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// As these two impls would overlap we forbid any impls which
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// have a type parameter in front of a local type.
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//
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// With const parameters this issue does not exist as there are no
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// constants local to another downstream crate.
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struct Local2;
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impl<const N: usize> Trait<N, Local2> for i32 {}
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fn main() {}
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