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Diffstat (limited to 'src/test/ui/coherence/coherence-fn-inputs.rs')
| -rw-r--r-- | src/test/ui/coherence/coherence-fn-inputs.rs | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/test/ui/coherence/coherence-fn-inputs.rs b/src/test/ui/coherence/coherence-fn-inputs.rs new file mode 100644 index 000000000..3afec5c54 --- /dev/null +++ b/src/test/ui/coherence/coherence-fn-inputs.rs @@ -0,0 +1,25 @@ +// Test that we consider these two types completely equal: +// +// * `for<'a, 'b> fn(&'a u32, &'b u32)` +// * `for<'c> fn(&'c u32, &'c u32)` +// +// For a long time we considered these to be distinct types. But in fact they +// are equivalent, if you work through the implications of subtyping -- this is +// because: +// +// * `'c` can be the intersection of `'a` and `'b` (and there is always an intersection) +// * `'a` and `'b` can both be equal to `'c` + +trait Trait {} +impl Trait for for<'a, 'b> fn(&'a u32, &'b u32) {} +impl Trait for for<'c> fn(&'c u32, &'c u32) { + //~^ ERROR conflicting implementations + // + // Note in particular that we do NOT get a future-compatibility warning + // here. This is because the new leak-check proposed in [MCP 295] does not + // "error" when these two types are equated. + // + // [MCP 295]: https://github.com/rust-lang/compiler-team/issues/295 +} + +fn main() {} |