src/test/run-pass/associated-types-impl-redirect.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Test how resolving a projection interacts with inference.  In this
  12 // case, we were eagerly unifying the type variable for the iterator
  13 // type with `I` from the where clause, ignoring the in-scope `impl`
  14 // for `ByRef`. The right answer was to consider the result ambiguous
  15 // until more type information was available.
  16
  17 #![feature(lang_items, unboxed_closures)]
  18 #![no_implicit_prelude]
  19
  20 use std::marker::Sized;
  21 use std::option::Option::{None, Some, self};
  22
  23 trait Iterator {
  24     type Item;
  25
  26     fn next(&mut self) -> Option<Self::Item>;
  27 }
  28
  29 trait IteratorExt: Iterator + Sized {
  30     fn by_ref(&mut self) -> ByRef<Self> {
  31         ByRef(self)
  32     }
  33 }
  34
  35 impl<I> IteratorExt for I where I: Iterator {}
  36
  37 struct ByRef<'a, I: 'a + Iterator>(&'a mut I);
  38
  39 impl<'a, I: Iterator> Iterator for ByRef<'a, I> {
  40     type Item = I::Item;
  41
  42     fn next(&mut self) -> Option< <I as Iterator>::Item > {
  43         self.0.next()
  44     }
  45 }
  46
  47 fn is_iterator_of<A, I: Iterator<Item=A>>(_: &I) {}
  48
  49 fn test<A, I: Iterator<Item=A>>(mut it: I) {
  50     is_iterator_of::<A, _>(&it.by_ref());
  51 }
  52
  53 fn test2<A, I1: Iterator<Item=A>, I2: Iterator<Item=I1::Item>>(mut it: I2) {
  54     is_iterator_of::<A, _>(&it)
  55 }
  56
  57 fn main() { }