There's a group of methods in `DeclContext` with names that start with *is*,
such as `isClassOrClassExtensionContext()`. These names suggests a boolean
return value, while the methods actually return a type declaration. This
patch replaces the *is* prefix with *getAs* to better reflect their interface.
This is necessary for some other work I'm doing, which really wants
paramdecls to have reasonable declcontexts. It is also a small step
towards generic subscripts.
Only use the existing type checker (via "TC") in the iterative type
checker when we're actually making use of its functionality. The
intent is to drive this usage down to zero as we port code over to the
iterative type checker, so unprincipled uses get in the way.
Swift SVN r32573
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
