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Diffstat (limited to '')
-rw-r--r-- | src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs b/src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs new file mode 100644 index 000000000..f2a4c6e42 --- /dev/null +++ b/src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs @@ -0,0 +1,46 @@ +// run-pass +#![allow(dead_code)] +#![allow(unused_imports)] +// Test how resolving a projection interacts with inference. In this +// case, we were eagerly unifying the type variable for the iterator +// type with `I` from the where clause, ignoring the in-scope `impl` +// for `ByRef`. The right answer was to consider the result ambiguous +// until more type information was available. + +#![feature(lang_items)] +#![no_implicit_prelude] + +use std::marker::Sized; +use std::option::Option::{None, Some, self}; + +trait Iterator { + type Item; + + fn next(&mut self) -> Option<Self::Item>; +} + +trait IteratorExt: Iterator + Sized { + fn by_ref(&mut self) -> ByRef<Self> { + ByRef(self) + } +} + +impl<I> IteratorExt for I where I: Iterator {} + +struct ByRef<'a, I: 'a + Iterator>(&'a mut I); + +impl<'a, A, I> Iterator for ByRef<'a, I> where I: Iterator<Item=A> { + type Item = A; + + fn next(&mut self) -> Option< <I as Iterator>::Item > { + self.0.next() + } +} + +fn is_iterator_of<A, I: Iterator<Item=A>>(_: &I) {} + +fn test<A, I: Iterator<Item=A>>(mut it: I) { + is_iterator_of::<A, _>(&it.by_ref()); +} + +fn main() { } |