Creating accessors for a storage declaration within validateDecl() caused
circular dependencies detected by the request-evaluator. Separate out
accessor creation to break the dependency.
Fixes SR-8656 / rdar://problem/43951634.
When we're marking a declaration as @objc and recording it in the
class and source-file lookup tables (for @objc collision detection),
don't cause a cycle by querying `getObjCSelector()`. This is somewhat
of a hack: a better long-term approach would be to move the recording
much later, and request'ify the name computation. That'll be follow-up
work.
We weren’t getting anything out of the check for the extended nominal
declaration of an extension within unqualified name lookup except
some spurious cycles in the request-evaluator. Stop doing this.
Put in some rudimentary logic for finding circular references within
the iterative type checker and diagnosing those cycles. The
"rudimentary" part is because we're performing linear searches within
a stack rather than keeping a proper dependency graph, which is
inefficient and could display longer cycles than are actually
present. Additionally, the diagnostic is not specialized to the actual
query, so we get a generic "circular reference" diagnostic. OTOH, we
show all of the declarations involved in the cycle, which at least
lets the user figure out where the cycle occurred.
Enable the iterative type checker for resolving the type of a global
typealiases.
Swift SVN r32572
