Use equivalence classes for visible-name lookup into type parameters.

Author: DougGregor

lib/AST/LookupVisibleDecls.cpp

@@ -564,26 +564,26 @@ static void lookupVisibleMemberDeclsImpl(
   // If we're looking into a type parameter and we have a generic signature
   // builder, use the GSB to resolve where we should look.
   if (BaseTy->isTypeParameter() && GSB) {
-    auto PA = GSB->resolveArchetype(
-                BaseTy,
-                ArchetypeResolutionKind::CompleteWellFormed);
-    if (!PA) return;
+    auto EquivClass =
+      GSB->resolveEquivalenceClass(BaseTy,
+                                   ArchetypeResolutionKind::CompleteWellFormed);
+    if (!EquivClass) return;
 
-    if (auto Concrete = PA->getConcreteType()) {
-      BaseTy = Concrete;
+    if (EquivClass->concreteType) {
+      BaseTy = EquivClass->concreteType;
     } else {
       // Conformances
-      for (auto Proto : PA->getConformsTo()) {
+      for (const auto &Conforms : EquivClass->conformsTo) {
         lookupVisibleProtocolMemberDecls(
-            BaseTy, Proto->getDeclaredType(), Consumer, CurrDC, LS,
-            getReasonForSuper(Reason), TypeResolver, GSB, Visited);
+            BaseTy, Conforms.first->getDeclaredType(), Consumer, CurrDC,
+            LS, getReasonForSuper(Reason), TypeResolver, GSB, Visited);
       }
 
       // Superclass.
-      if (auto Superclass = PA->getSuperclass()) {
-        lookupVisibleMemberDeclsImpl(Superclass, Consumer, CurrDC, LS,
-                                     getReasonForSuper(Reason), TypeResolver,
-                                     GSB, Visited);
+      if (EquivClass->superclass) {
+        lookupVisibleMemberDeclsImpl(EquivClass->superclass, Consumer, CurrDC,
+                                     LS, getReasonForSuper(Reason),
+                                     TypeResolver, GSB, Visited);
       }
       return;
     }