HasMemberExpressionAmbiguity

A common trait for classes, in which supposed member expressions (and thus also member calls) in the form of "a.b" have an ambiguity between a real field/method access (when "a" is an object) and a qualified call because of an import, if "a" is an import / namespace.

We can only resolve this after we have dealt with imports and know all symbols. Therefore, we invoke the ResolveMemberExpressionAmbiguityPass.