duplicates:

• SR-5556 @escaping Diagnostics Should Always Offer a Fixit

Issue Description:

The compiler is not providing automatic fix-it suggestions for returning closures that are not properly labeled with a `@escaping` keyword.

For example, here is an incorrect version of a function that requires two `@escaping` keywords to be inserted.

func mapping <A, B, C> (f: (A) -> (B)) -> ((C, B) -> (C)) -> ((C, A) -> (C))

Despite the complexity, the compiler manages to catch two errors but fails to provide a fix-it for the latter.

1. Closure use of non-escaping parameter `f` may allow it to escape
 a. Automatic Fix-it by doing `f: @escaping (A) - > (B)`

2. Closure use of non-escaping parameter `reducer` may allow it to escape
 b. No Fix-it provided

As you see above, the two places where a compile-time error occurred had the same exact problem; they both needed a `@escaping`. However, while the function parameter was offered an automatic fix-it, the nested closure being returned was not.

Here’s the correct version of the function.

func mapping <A, B, C> (f: @escaping (A) -> (B)) -> (@escaping ((C, B) -> (C))) -> ((C, A) -> (C)) {
    return { reducer in
        return { accum, input in
            reducer(accum, f(input))
        }
    }
}