Use ExtensionDecl::getExtendedNominal() to wire up extensions to their
nominal types early in type checking (the bindExtensions()) operation,
rather than going through type validation to do so.
The parser was using an AST-level name lookup operation to provide a
slightly improved diagnostic (suggesting "self." if there was a member
of that name in the enclosing type context). This is a fairly unfortunate
layering violation: name lookup cannot produce correct results at this
point. Remove the custom diagnostic and the lookup; this can come back
when all lookup moves out of the parser.
...and collapse StaticVar/ClassVar and StaticLet/ClassLet into
StaticProperty/ClassProperty.
"var" and "let" aren't great nouns to use in diagnostics to begin with,
especially alongside semantic terms like "instance method". Focus on
the type vs. non-type aspect instead with "property", which better
matches how people talk about member vars (and lets) anyway.
This crash happens because shouldAddSelfFixit (a check for the expected_self_before_reference diagnotic) performs name lookup inside the parser, which causes a search for extensions, which triggers the mangler, which can get confused if we are in an unfinished declaration (a PatternBindingInitilizer in this case).
A cleaner fix would be to move that logic inside Sema, but it would require much more refactoring that I don’t feel comfortable doing. Instead, this band-aid checks if the innermost type is inside a local context. If that’s the case, we can ignore the search for extensions.
This fixit checks if a decl with the identical name can be found in the parent type
context; if can, we add "self." to try to resolve the issue. rdar://25389852
