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Issue Description:

@dynamicMemberLookup
struct A {
    var foo = [String]()
    subscript(dynamicMember member: String) -> A {
        A(foo: foo + [member])
    }
    subscript(dynamicMember keyPath: KeyPath<B, B>) -> A {
        A(foo: foo + B()[keyPath: keyPath].bar)
    }
}


@dynamicMemberLookup
struct B {
    var bar = [String()]
    subscript(dynamicMember member: String) -> B {
        B(bar: bar + [member])
    }
}


let a = A().hello.world

Potential Source of Error

I am pretty sure that this error occurs because, since A has a dynamic member subscript that takes KeyPath<B, B>, there is a conflict between the dynamic member subscripts that take a string defined on A and B.

Xcode Response

This makes Xcode display a banner saying "An internal error occurred. Source editor functionality is limited. Attempting to restore...". When running it, a "Segmentation fault: 11" error is emitted (the build log is attached).

Environment

I found this bug to be present from Xcode Version 11.3.1 (11C504) to Xcode Version 11.4 beta 3 (11N132i).