src/test/run-pass/coerce-unify.rs

   1 // Copyright 2016 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 // Check that coercions can unify if-else, match arms and array elements.
  12
  13 // Try to construct if-else chains, matches and arrays out of given expressions.
  14 macro_rules! check {
  15     ($last:expr $(, $rest:expr)+) => {
  16         // Last expression comes first because of whacky ifs and matches.
  17         let _ = $(if false { $rest })else+ else { $last };
  18
  19         let _ = match 0 { $(_ if false => $rest,)+ _ => $last };
  20
  21         let _ = [$($rest,)+ $last];
  22     }
  23 }
  24
  25 // Check all non-uniform cases of 2 and 3 expressions of 2 types.
  26 macro_rules! check2 {
  27     ($a:expr, $b:expr) => {
  28         check!($a, $b);
  29         check!($b, $a);
  30
  31         check!($a, $a, $b);
  32         check!($a, $b, $a);
  33         check!($a, $b, $b);
  34
  35         check!($b, $a, $a);
  36         check!($b, $a, $b);
  37         check!($b, $b, $a);
  38     }
  39 }
  40
  41 // Check all non-uniform cases of 2 and 3 expressions of 3 types.
  42 macro_rules! check3 {
  43     ($a:expr, $b:expr, $c:expr) => {
  44         // Delegate to check2 for cases where a type repeats.
  45         check2!($a, $b);
  46         check2!($b, $c);
  47         check2!($a, $c);
  48
  49         // Check the remaining cases, i.e. permutations of ($a, $b, $c).
  50         check!($a, $b, $c);
  51         check!($a, $c, $b);
  52         check!($b, $a, $c);
  53         check!($b, $c, $a);
  54         check!($c, $a, $b);
  55         check!($c, $b, $a);
  56     }
  57 }
  58
  59 use std::mem::size_of;
  60
  61 fn foo() {}
  62 fn bar() {}
  63
  64 pub fn main() {
  65     check3!(foo, bar, foo as fn());
  66     check3!(size_of::<u8>, size_of::<u16>, size_of::<usize> as fn() -> usize);
  67
  68     let s = String::from("bar");
  69     check2!("foo", &s);
  70
  71     let a = [1, 2, 3];
  72     let v = vec![1, 2, 3];
  73     check2!(&a[..], &v);
  74
  75     // Make sure in-array coercion still works.
  76     let _ = [("a", Default::default()), (Default::default(), "b"), (&s, &s)];
  77 }