src/test/ui/rfc1445/phantom-data-is-structurally-matchable.rs

   1 // run-pass
   2
   3 // This file checks that `PhantomData` is considered structurally matchable.
   4
   5 use std::marker::PhantomData;
   6
   7 fn main() {
   8     let mut count = 0;
   9
  10     // A type which is not structurally matchable:
  11     struct NotSM;
  12
  13     // And one that is:
  14     #[derive(PartialEq, Eq)]
  15     struct SM;
  16
  17     // Check that SM is structural-match:
  18     const CSM: SM = SM;
  19     match SM {
  20         CSM => count += 1,
  21     };
  22
  23     // Check that PhantomData<T> is structural-match even if T is not.
  24     const CPD1: PhantomData<NotSM> = PhantomData;
  25     match PhantomData {
  26         CPD1 => count += 1,
  27     };
  28
  29     // Check that PhantomData<T> is structural-match when T is.
  30     const CPD2: PhantomData<SM> = PhantomData;
  31     match PhantomData {
  32         CPD2 => count += 1,
  33     };
  34
  35     // Check that a type which has a PhantomData is structural-match.
  36     #[derive(PartialEq, Eq, Default)]
  37     struct Foo {
  38         alpha: PhantomData<NotSM>,
  39         beta: PhantomData<SM>,
  40     }
  41
  42     const CFOO: Foo = Foo {
  43         alpha: PhantomData,
  44         beta: PhantomData,
  45     };
  46
  47     match Foo::default() {
  48         CFOO => count += 1,
  49     };
  50
  51     // Final count must be 4 now if all
  52     assert_eq!(count, 4);
  53 }