When we have a value 'p' of type 'P.Type' for some protocol 'P',
we require the user to write 'p.init()' rather than 'p()' to
construct an instance of a concrete type conforming to 'P'.
If they write 'p()', we suggest a fixit to insert '.init',
however if there is also a subsequent member access on the
result, for example 'p().foo', we would crash.
Another invalid case that used to crash is when you construct
a protocol metatype directly and then access a member of it,
eg. 'P().foo'.
