Mark as "synthesized" type aliases for inferred associated type witnesses

(cherry picked from commit 76e6f15)

Author: DougGregor

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -2129,7 +2129,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
     TypeChecker::checkDeclAttributes(CD);
 
-    for (Decl *Member : CD->getAllMembers())
+    for (Decl *Member : CD->getABIMembers())
       visit(Member);
 
     TypeChecker::checkPatternBindingCaptures(CD);

lib/Sema/TypeCheckProtocol.cpp

@@ -2925,6 +2925,7 @@ void ConformanceChecker::recordTypeWitness(AssociatedTypeDecl *assocType,
     aliasDecl->setUnderlyingType(type);
 
     aliasDecl->setImplicit();
+    aliasDecl->setSynthesized();
     if (type->hasError())
       aliasDecl->setInvalid();