Sema: Fix unqualified lookup performed for DefineMemberBasedOnUnintendedGenericParam fix

We want to look for protocols at the top level, and not names visible from
the function body. Previously we were passing the function's parent
DeclContext and the source location of the parameter, but this will no
longer work, so pass the SourceFile and an empty source location instead.

Author: slavapestov

lib/Sema/CSSimplify.cpp

@@ -7289,8 +7289,8 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyMemberConstraint(
 
           auto descriptor = UnqualifiedLookupDescriptor(
               DeclNameRef(param->getName()),
-              paramDecl->getDeclContext()->getParentForLookup(),
-              paramDecl->getStartLoc(),
+              paramDecl->getDeclContext()->getParentSourceFile(),
+              SourceLoc(),
               UnqualifiedLookupFlags::KnownPrivate |
                   UnqualifiedLookupFlags::TypeLookup);
           auto lookup = evaluateOrDefault(