swift234

[Type checker SR-899] Warning on missing ".self" for single-parameter functions.

Due to a modeling error in the type checker's folding of type
references into type expressions, code such as "strideof(Int)" would
be accepted without the required ".self". Commit
4a60b6cbf4fa2a410aebf7f725865395c99ef6ca fixes the modeling issue but
left the historical accepts-invalid; now, diagnose these cases with a
warning + Fix-It to ease the transition.

Fixes SR-899.