[proposal] Ensure broadest interface

[gatesn]

What happened?

I have a constructor that accepts a Foo, where Foo implements/extends Bar.

My class only uses methods from Bar though, so the argument it accepts is overly restrictive.

What did you want to happen?

Warn me when I take a more specific class when a superclass / interface would suffice.

However...

This probably breaks for semantic behavior. e.g. ThreadSafeFoo implements Foo. Maybe an annotation denoting a semantic extension could be added?