Opaque result types

[rintaro (Rintaro Ishizaki)]

@Douglas_Gregor

//------ Module A
public protocol P {}
private func generateP() -> opaque P { ... }

public var globalValue1 = generateP()
public var globalValue2 = generateP()

//------ module main
import A
globalValue1 = globalValue2

Is this legal because the types of globalValue1 and globalValue2 are both "the opaque return type of generateP() "? If so, how the compiler knows those are the same types, from the .moduleinterface ?

Both globalValue1 and globalValue2 have inferred the type "opaque result type of generateP() ", so they are known to have the same type.

My question is how .swiftinterface describes globalValue1 and globalValue2 has the same type?
In this case, .swiftinterface for module A would be:

public protocol P {
}
public var globalValue1: opaque P { get set }
public var globalValue2: opaque P { get set }

We can't expose generateP() here, right?