[NFC] AST: Define TypeRepr::isParenType()

Author: AnthonyLatsis

include/swift/AST/TypeRepr.h

@@ -184,6 +184,10 @@ class alignas(1 << TypeReprAlignInBits) TypeRepr
   /// opaque return type reprs.
   bool hasOpaque();
 
+  /// Returns a Boolean value indicating whether this written type is
+  /// parenthesized, that is, matches the following grammar: `'(' type ')'`.
+  bool isParenType() const;
+
   /// Retrieve the type repr without any parentheses around it.
   ///
   /// The use of this function must be restricted to contexts where

lib/AST/TypeRepr.cpp

@@ -109,14 +109,18 @@ bool TypeRepr::hasOpaque() {
     findIf([](TypeRepr *ty) { return isa<OpaqueReturnTypeRepr>(ty); });
 }
 
+bool TypeRepr::isParenType() const {
+  auto *tuple = dyn_cast<TupleTypeRepr>(this);
+  return tuple && tuple->isParenType();
+}
+
 TypeRepr *TypeRepr::getWithoutParens() const {
-  auto *repr = const_cast<TypeRepr *>(this);
-  while (auto *tupleRepr = dyn_cast<TupleTypeRepr>(repr)) {
-    if (!tupleRepr->isParenType())
-      break;
-    repr = tupleRepr->getElementType(0);
+  auto *result = this;
+  while (result->isParenType()) {
+    result = cast<TupleTypeRepr>(result)->getElementType(0);
   }
-  return repr;
+
+  return const_cast<TypeRepr *>(result);
 }
 
 bool TypeRepr::isSimpleUnqualifiedIdentifier(Identifier identifier) const {