src/test/ui/specialization/non-defaulted-item-fail.rs

   1 #![feature(specialization, associated_type_defaults)]
   2 //~^ WARN the feature `specialization` is incomplete
   3
   4 // Test that attempting to override a non-default method or one not in the
   5 // parent impl causes an error.
   6
   7 trait Foo {
   8     type Ty = ();
   9     const CONST: u8 = 123;
  10     fn foo(&self) -> bool { true }
  11 }
  12
  13 // Specialization tree for Foo:
  14 //
  15 //       Box<T>              Vec<T>
  16 //        / \                 / \
  17 // Box<i32>  Box<i64>   Vec<()>  Vec<bool>
  18
  19 impl<T> Foo for Box<T> {
  20     type Ty = bool;
  21     const CONST: u8 = 0;
  22     fn foo(&self) -> bool { false }
  23 }
  24
  25 // Allowed
  26 impl Foo for Box<i32> {}
  27
  28 // Can't override a non-`default` fn
  29 impl Foo for Box<i64> {
  30     type Ty = Vec<()>;
  31 //~^ error: `Ty` specializes an item from a parent `impl`, but that item is not marked `default`
  32     const CONST: u8 = 42;
  33 //~^ error: `CONST` specializes an item from a parent `impl`, but that item is not marked `default`
  34     fn foo(&self) -> bool { true }
  35 //~^ error: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
  36 }
  37
  38
  39 // Doesn't mention the item = provided body/value is used and the method is final.
  40 impl<T> Foo for Vec<T> {}
  41
  42 // Allowed
  43 impl Foo for Vec<()> {}
  44
  45 impl Foo for Vec<bool> {
  46     type Ty = Vec<()>;
  47 //~^ error: `Ty` specializes an item from a parent `impl`, but that item is not marked `default`
  48     const CONST: u8 = 42;
  49 //~^ error: `CONST` specializes an item from a parent `impl`, but that item is not marked `default`
  50     fn foo(&self) -> bool { true }
  51 //~^ error: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
  52 }
  53
  54 fn main() {}