Slava Pestov 39b697898a Sema: Fix for unbound generic type handling ...

Previously we prohibited unbound generics in the underlying
type of a typealias, but due to an oversight the check was
not performed when resolving a nested type.

So this worked:

struct Outer { struct Inner<T> {} }
typealias OuterInner = Outer.Inner
let _: OuterInner<Int> = Outer.Inner<Int>()

However it was easy to cause a crash this way by stating an
unbound generic type where one was not expected. Also,
unqualified types in a typealias did not get this treatment,
so the following did not work:

typealias MyOptional = Optional

Formalize the old behavior by allowing unbound generic types
in the underlying type of a typealias, while otherwise
prohibiting unbound references to nested types.

2017-04-23 00:02:29 -07:00

13 KiB

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