src/test/ui/coercion/coerce-unify.rs

   1 // run-pass
   2 // Check that coercions can unify if-else, match arms and array elements.
   3
   4 // Try to construct if-else chains, matches and arrays out of given expressions.
   5 macro_rules! check {
   6     ($last:expr $(, $rest:expr)+) => {
   7         // Last expression comes first because of whacky ifs and matches.
   8         let _ = $(if false { $rest })else+ else { $last };
   9
  10         let _ = match 0 { $(_ if false => $rest,)+ _ => $last };
  11
  12         let _ = [$($rest,)+ $last];
  13     }
  14 }
  15
  16 // Check all non-uniform cases of 2 and 3 expressions of 2 types.
  17 macro_rules! check2 {
  18     ($a:expr, $b:expr) => {
  19         check!($a, $b);
  20         check!($b, $a);
  21
  22         check!($a, $a, $b);
  23         check!($a, $b, $a);
  24         check!($a, $b, $b);
  25
  26         check!($b, $a, $a);
  27         check!($b, $a, $b);
  28         check!($b, $b, $a);
  29     }
  30 }
  31
  32 // Check all non-uniform cases of 2 and 3 expressions of 3 types.
  33 macro_rules! check3 {
  34     ($a:expr, $b:expr, $c:expr) => {
  35         // Delegate to check2 for cases where a type repeats.
  36         check2!($a, $b);
  37         check2!($b, $c);
  38         check2!($a, $c);
  39
  40         // Check the remaining cases, i.e., permutations of ($a, $b, $c).
  41         check!($a, $b, $c);
  42         check!($a, $c, $b);
  43         check!($b, $a, $c);
  44         check!($b, $c, $a);
  45         check!($c, $a, $b);
  46         check!($c, $b, $a);
  47     }
  48 }
  49
  50 use std::mem::size_of;
  51
  52 fn foo() {}
  53 fn bar() {}
  54
  55 pub fn main() {
  56     check3!(foo, bar, foo as fn());
  57     check3!(size_of::<u8>, size_of::<u16>, size_of::<usize> as fn() -> usize);
  58
  59     let s = String::from("bar");
  60     check2!("foo", &s);
  61
  62     let a = [1, 2, 3];
  63     let v = vec![1, 2, 3];
  64     check2!(&a[..], &v);
  65
  66     // Make sure in-array coercion still works.
  67     let _ = [("a", Default::default()), (Default::default(), "b"), (&s, &s)];
  68 }