Open Radar

 
Summary:
I have a protocol extension to which I have added extensions defining much of the behaviour of my system. Several methods use the same dictionary type involving Self for different purposes, so I made a typealias for each different purpose as documentation. This causes typechecking to fail.


Steps to Reproduce:
1. This code:
protocol P {}

extension P {
	typealias T = [String:Self]
}

extension P {
	func f(t: T) {
		g(t)
	}

	func g(t: T) {}
}


Expected Results:
should typecheck


Actual Results:
but totally doesn’t:
boom.swift:9:5: error: cannot convert value of type '[String : Self]' to expected argument type '[String : _]'
                g(t)
                  ^


Regression:
It seems to be fine if `f`’s parameter type is changed from `T` to `[String:Self]`. I.e. it can match `[String:Self]` against the type `T` in `g`’s definition, but it can’t match `T` against `T`.


Notes:
N/A