src/test/run-pass/assignability-trait.rs

   1 // Copyright 2012-4 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 // Tests that type assignability is used to search for instances when
  12 // making method calls, but only if there aren't any matches without
  13 // it.
  14
  15 trait iterable<A> {
  16     fn iterate<F>(&self, blk: F) -> bool where F: FnMut(&A) -> bool;
  17 }
  18
  19 impl<'a,A> iterable<A> for &'a [A] {
  20     fn iterate<F>(&self, f: F) -> bool where F: FnMut(&A) -> bool {
  21         self.iter().all(f)
  22     }
  23 }
  24
  25 impl<A> iterable<A> for Vec<A> {
  26     fn iterate<F>(&self, f: F) -> bool where F: FnMut(&A) -> bool {
  27         self.iter().all(f)
  28     }
  29 }
  30
  31 fn length<A, T: iterable<A>>(x: T) -> usize {
  32     let mut len = 0;
  33     x.iterate(|_y| {
  34         len += 1;
  35         true
  36     });
  37     return len;
  38 }
  39
  40 pub fn main() {
  41     let x: Vec<isize> = vec![0,1,2,3];
  42     // Call a method
  43     x.iterate(|y| { assert_eq!(x[*y as usize], *y); true });
  44     // Call a parameterized function
  45     assert_eq!(length(x.clone()), x.len());
  46     // Call a parameterized function, with type arguments that require
  47     // a borrow
  48     assert_eq!(length::<isize, &[isize]>(&*x), x.len());
  49
  50     // Now try it with a type that *needs* to be borrowed
  51     let z = [0,1,2,3];
  52     // Call a parameterized function
  53     assert_eq!(length::<isize, &[isize]>(&z), z.len());
  54 }