[NFC] AST: Consolidate some repeated DependentMemberType logic in Type methods

Author: AnthonyLatsis

include/swift/AST/Types.h

@@ -821,6 +821,12 @@ class alignas(1 << TypeAlignInBits) TypeBase
   /// type variables referenced by this type.
   void getTypeVariables(SmallPtrSetImpl<TypeVariableType *> &typeVariables);
 
+private:
+  /// If the receiver is a `DependentMemberType`, returns its root. Otherwise,
+  /// returns the receiver.
+  Type getDependentMemberRoot();
+
+public:
   /// Determine whether this type is a type parameter, which is either a
   /// GenericTypeParamType or a DependentMemberType.
   ///
@@ -7862,38 +7868,11 @@ inline ASTContext &TypeBase::getASTContext() const {
   return *const_cast<ASTContext*>(getCanonicalType()->Context);
 }
 
-inline bool TypeBase::isTypeVariableOrMember() {
-  Type t(this);
-
-  while (auto *memberTy = t->getAs<DependentMemberType>())
-    t = memberTy->getBase();
-
-  return t->is<TypeVariableType>();
-}
-
-inline bool TypeBase::isTypeParameter() {
-  Type t(this);
-
-  while (auto *memberTy = t->getAs<DependentMemberType>())
-    t = memberTy->getBase();
-
-  return t->is<GenericTypeParamType>();
-}
-
 // TODO: This will become redundant once InOutType is removed.
 inline bool TypeBase::isMaterializable() {
   return !(hasLValueType() || is<InOutType>());
 }
 
-inline GenericTypeParamType *TypeBase::getRootGenericParam() {
-  Type t(this);
-
-  while (auto *memberTy = t->getAs<DependentMemberType>())
-    t = memberTy->getBase();
-
-  return t->castTo<GenericTypeParamType>();
-}
-
 inline bool TypeBase::isConstraintType() const {
   return getCanonicalType().isConstraintType();
 }

lib/AST/ParameterPack.cpp

@@ -177,12 +177,7 @@ void TypeBase::getTypeParameterPacks(
 }
 
 bool TypeBase::isParameterPack() {
-  Type t(this);
-
-  while (auto *memberTy = t->getAs<DependentMemberType>())
-    t = memberTy->getBase();
-
-  return t->isRootParameterPack();
+  return getDependentMemberRoot()->isRootParameterPack();
 }
 
 bool TypeBase::isRootParameterPack() {

lib/AST/Type.cpp

@@ -603,6 +603,27 @@ void TypeBase::getTypeVariables(
          "Did not find type variables!");
 }
 
+Type TypeBase::getDependentMemberRoot() {
+  Type t(this);
+
+  while (auto *dmt = t->getAs<DependentMemberType>())
+    t = dmt->getBase();
+
+  return t;
+}
+
+bool TypeBase::isTypeVariableOrMember() {
+  return getDependentMemberRoot()->is<TypeVariableType>();
+}
+
+bool TypeBase::isTypeParameter() {
+  return getDependentMemberRoot()->is<GenericTypeParamType>();
+}
+
+GenericTypeParamType *TypeBase::getRootGenericParam() {
+  return getDependentMemberRoot()->castTo<GenericTypeParamType>();
+}
+
 static bool isLegalSILType(CanType type);
 
 static bool isLegalSILTypeOrPackExpansion(CanType type) {

lib/IRGen/GenMeta.cpp

@@ -2758,15 +2758,10 @@ ProtocolDecl *irgen::opaqueTypeRequiresWitnessTable(
 
   // The type itself must be anchored on one of the generic parameters of
   // the opaque type (not an outer context).
-  Type subject = req.getFirstType();
-  while (auto depMember = subject->getAs<DependentMemberType>()) {
-    subject = depMember->getBase();
-  }
-
-  if (auto genericParam = subject->getAs<GenericTypeParamType>()) {
-    unsigned opaqueDepth = opaque->getOpaqueGenericParams().front()->getDepth();
-    if (genericParam->getDepth() == opaqueDepth)
-      return proto;
+  auto *genericParam = req.getFirstType()->getRootGenericParam();
+  unsigned opaqueDepth = opaque->getOpaqueGenericParams().front()->getDepth();
+  if (genericParam->getDepth() == opaqueDepth) {
+    return proto;
   }
 
   return nullptr;