src/test/run-pass/issue-2185.rs

   1 // Copyright 2012-2014 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 // ignore-test
  12
  13 // notes on this test case:
  14 // On Thu, Apr 18, 2013-2014 at 6:30 PM, John Clements <clements@brinckerhoff.org> wrote:
  15 // the "issue-2185.rs" test was ignored with a ref to #2263. Issue #2263 is now fixed,
  16 // so I tried it again, and after adding some &self parameters, I got this error:
  17 //
  18 // Running /usr/local/bin/rustc:
  19 // issue-2185.rs:24:0: 26:1 error: conflicting implementations for a trait
  20 // issue-2185.rs:24 impl iterable<usize> for 'static ||usize|| {
  21 // issue-2185.rs:25     fn iter(&self, blk: |v: usize|) { self( |i| blk(i) ) }
  22 // issue-2185.rs:26 }
  23 // issue-2185.rs:20:0: 22:1 note: note conflicting implementation here
  24 // issue-2185.rs:20 impl<A> iterable<A> for 'static ||A|| {
  25 // issue-2185.rs:21     fn iter(&self, blk: |A|) { self(blk); }
  26 // issue-2185.rs:22 }
  27 //
  28 // … so it looks like it's just not possible to implement both
  29 // the generic iterable<usize> and iterable<A> for the type iterable<usize>.
  30 // Is it okay if I just remove this test?
  31 //
  32 // but Niko responded:
  33 // think it's fine to remove this test, just because it's old and cruft and not hard to reproduce.
  34 // *However* it should eventually be possible to implement the same interface for the same type
  35 // multiple times with different type parameters, it's just that our current trait implementation
  36 // has accidental limitations.
  37
  38 // so I'm leaving it in.
  39 // actually, it looks like this is related to bug #3429. I'll rename this bug.
  40
  41 // This test had to do with an outdated version of the iterable trait.
  42 // However, the condition it was testing seemed complex enough to
  43 // warrant still having a test, so I inlined the old definitions.
  44
  45 trait iterable<A> {
  46     fn iter(&self, blk: |A|);
  47 }
  48
  49 impl<A> iterable<A> for 'static ||A|| {
  50     fn iter(&self, blk: |A|) { self(blk); }
  51 }
  52
  53 impl iterable<usize> for 'static ||usize|| {
  54     fn iter(&self, blk: |v: usize|) { self( |i| blk(i) ) }
  55 }
  56
  57 fn filter<A,IA:iterable<A>>(self: IA, prd: 'static |A| -> bool, blk: |A|) {
  58     self.iter(|a| {
  59         if prd(a) { blk(a) }
  60     });
  61 }
  62
  63 fn foldl<A,B,IA:iterable<A>>(self: IA, b0: B, blk: |B, A| -> B) -> B {
  64     let mut b = b0;
  65     self.iter(|a| {
  66         b = blk(b, a);
  67     });
  68     b
  69 }
  70
  71 fn range(lo: usize, hi: usize, it: |usize|) {
  72     let mut i = lo;
  73     while i < hi {
  74         it(i);
  75         i += 1;
  76     }
  77 }
  78
  79 pub fn main() {
  80     let range: 'static ||usize|| = |a| range(0, 1000, a);
  81     let filt: 'static ||v: usize|| = |a| filter(
  82         range,
  83         |&&n: usize| n % 3 != 0 && n % 5 != 0,
  84         a);
  85     let sum = foldl(filt, 0, |accum, &&n: usize| accum + n );
  86
  87     println!("{}", sum);
  88 }