src/test/ui/lub-glb/old-lub-glb-hr-noteq2.rs

   1 // Test taking the LUB of two function types that are not equatable but where
   2 // one is more general than the other. Test the case where the more general type
   3 // (`x`) is the second match arm specifically.
   4 //
   5 // FIXME(#73154) Pure NLL checker without leak check accepts this test.
   6 // (Note that it still errors in old-lub-glb-hr-noteq1.rs). What happens
   7 // is that, due to the ordering of the match arms, we pick the correct "more
   8 // general" fn type, and we ignore the errors from the non-NLL type checker that
   9 // requires equality. The NLL type checker only requires a subtyping
  10 // relationship, and that holds. To unblock landing NLL - and ensure that we can
  11 // choose to make this always in error in the future - we perform the leak check
  12 // after coercing a function pointer.
  13
  14 // revisions: leak noleak
  15 //[noleak] compile-flags: -Zno-leak-check
  16
  17 //[noleak] check-pass
  18
  19 fn foo(x: for<'a, 'b> fn(&'a u8, &'b u8) -> &'a u8, y: for<'a> fn(&'a u8, &'a u8) -> &'a u8) {
  20     // The two types above are not equivalent. With the older LUB/GLB
  21     // algorithm, this may have worked (I don't remember), but now it
  22     // doesn't because we require equality.
  23     let z = match 22 {
  24         0 => y,
  25         _ => x,
  26         //[leak]~^ ERROR `match` arms have incompatible types
  27     };
  28 }
  29
  30 fn foo_cast(x: for<'a, 'b> fn(&'a u8, &'b u8) -> &'a u8, y: for<'a> fn(&'a u8, &'a u8) -> &'a u8) {
  31     // But we can *upcast* explicitly the type of `x` and figure
  32     // things out:
  33     let z = match 22 {
  34         0 => x as for<'a> fn(&'a u8, &'a u8) -> &'a u8,
  35         _ => y,
  36     };
  37 }
  38
  39 fn main() {}