diff options
| -rw-r--r-- | src/librustc/error_codes.rs | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/src/librustc/error_codes.rs b/src/librustc/error_codes.rs index e208e25f6ea..50b6ef57b55 100644 --- a/src/librustc/error_codes.rs +++ b/src/librustc/error_codes.rs @@ -259,8 +259,8 @@ trait Foo { This is similar to the second sub-error, but subtler. It happens in situations like the following: -```compile_fail -trait Super<A> {} +```compile_fail,E0038 +trait Super<A: ?Sized> {} trait Trait: Super<Self> { } @@ -270,17 +270,21 @@ struct Foo; impl Super<Foo> for Foo{} impl Trait for Foo {} + +fn main() { + let x: Box<dyn Trait>; +} ``` Here, the supertrait might have methods as follows: ``` -trait Super<A> { - fn get_a(&self) -> A; // note that this is object safe! +trait Super<A: ?Sized> { + fn get_a(&self) -> &A; // note that this is object safe! } ``` -If the trait `Foo` was deriving from something like `Super<String>` or +If the trait `Trait` was deriving from something like `Super<String>` or `Super<T>` (where `Foo` itself is `Foo<T>`), this is okay, because given a type `get_a()` will definitely return an object of that type. |