duplicates:

• SR-964 Warn if a computed property setter doesn't reference the new value

Issue Description:

Another developer recently mentioned that he spent two hours debugging a problem that came down to a property like this:

var foo: Foo {
  set { underlyingComponent.foo = foo } // this should have been `= newValue` ...
  get { return underlyingComponent.foo }
}

The compiler could have diagnosed this mistake by noticing that the newValue parameter was never referenced in the setter. It is difficult to imagine a setter which would not need to reference its newValue, and on the off chance somebody really does need to do so, you could silence the warning by ignoring the parameter with "set (_) {…}".