[SR-9040] Suggestion when overriding implictly unwrapped optional does not suggest making parameter implictly unwrapped

Previous ID	SR-9040
Radar	None
Original Reporter	@JosephDuffy
Type	Bug

Apple Swift version 4.2 (swiftlang-1000.11.37.1 clang-1000.11.45.1)
Target: x86_64-apple-darwin18.0.0

Votes	0
Component/s	Compiler
Labels	Bug, DiagnosticsQoI, StarterBug
Assignee	None
Priority	Medium

md5: 9b7c61d5cf17e72eb3e9d8e02cd54d9f

Issue Description:

When overriding a function that has an implicitly unwrapped optional parameter with a non-optional parameter, the fixit suggests adding ?, making the parameter optional.

I would expect this to offer adding !, along with ?, but I am not sure if this is classed as a bug, or an intentional change due to SE-0054.

Example code that produces the fixit:

class Foo {
    func bar(_ bar: String!) {}
}

class FooSubclass: Foo {
    override func bar(_ bar: String) {}
}

This produces the message: Cannot override instance method parameter of type 'String?' with non-optional type 'String', with an Insert '?' fix.

If this is classed as a bug I'd love to attempt to fix it)