[ParameterPack] Use the 'getTypeParameterPacks' utility when computing the

reduced shape of a given type that is not directly a pack type or archetype.

Author: hborla

lib/AST/ParameterPack.cpp

@@ -39,8 +39,7 @@ struct PackTypeParameterCollector: TypeWalker {
       if (paramTy->isParameterPack())
         typeParams.insert(paramTy);
     } else if (auto *archetypeTy = t->getAs<PackArchetypeType>()) {
-      if (archetypeTy->isRoot())
-        typeParams.insert(paramTy);
+      typeParams.insert(archetypeTy->getRoot());
     }
 
     return Action::Continue;
@@ -314,35 +313,20 @@ CanPackType PackType::getReducedShape() {
 }
 
 CanType TypeBase::getReducedShape() {
+  if (auto *packArchetype = getAs<PackArchetypeType>())
+     return packArchetype->getReducedShape();
+
   if (auto *packType = getAs<PackType>())
     return packType->getReducedShape();
 
   if (auto *expansionType = getAs<PackExpansionType>())
     return expansionType->getReducedShape();
 
-  struct PatternTypeWalker : public TypeWalker {
-    CanType shapeType;
-
-    Action walkToTypePre(Type type) override {
-      // Don't consider pack references inside nested pack
-      // expansion types.
-      if (type->is<PackExpansionType>()) {
-        return Action::Stop;
-      }
-
-      if (auto *archetype = type->getAs<PackArchetypeType>()) {
-        shapeType = archetype->getReducedShape();
-        return Action::Stop;
-      }
-
-      return Action::Continue;
-    }
-  } patternTypeWalker;
-
-  Type(this).walk(patternTypeWalker);
+  SmallVector<Type, 2> rootParameterPacks;
+  getTypeParameterPacks(rootParameterPacks);
 
-  if (patternTypeWalker.shapeType)
-    return patternTypeWalker.shapeType;
+  if (!rootParameterPacks.empty())
+    return rootParameterPacks.front()->getReducedShape();
 
   assert(!isTypeVariableOrMember());
   assert(!hasTypeParameter());