Add a Utility to Strip Parens from TypeReprs

Author: CodaFi

include/swift/AST/TypeRepr.h

@@ -172,6 +172,14 @@ class alignas(1 << TypeReprAlignInBits) TypeRepr
   /// `OpaqueReturnTypeRepr`s.
   CollectedOpaqueReprs collectOpaqueReturnTypeReprs();
 
+  /// Retrieve the type repr without any parentheses around it.
+  ///
+  /// The use of this function must be restricted to contexts where
+  /// user-written types are provided, and a syntactic analysis is appropriate.
+  /// Most use cases should analyze the resolved \c Type instead and use
+  /// \c Type::getCanonicalType() or \c Type::getWithoutParens().
+  TypeRepr *getWithoutParens() const;
+
   //*** Allocation Routines ************************************************/
 
   void print(raw_ostream &OS, const PrintOptions &Opts = PrintOptions()) const;

lib/AST/TypeRepr.cpp

@@ -102,6 +102,16 @@ bool TypeRepr::hasOpaque() {
     findIf([](TypeRepr *ty) { return isa<OpaqueReturnTypeRepr>(ty); });
 }
 
+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);
+  }
+  return repr;
+}
+
 CollectedOpaqueReprs TypeRepr::collectOpaqueReturnTypeReprs() {
   class Walker : public ASTWalker {
     CollectedOpaqueReprs &Reprs;

lib/Sema/TypeCheckDecl.cpp

@@ -2061,15 +2061,9 @@ ParamSpecifierRequest::evaluate(Evaluator &evaluator,
   assert(typeRepr != nullptr && "Should call setSpecifier() on "
          "synthesized parameter declarations");
 
-  auto *nestedRepr = typeRepr;
-
   // Look through parens here; other than parens, specifiers
   // must appear at the top level of a parameter type.
-  while (auto *tupleRepr = dyn_cast<TupleTypeRepr>(nestedRepr)) {
-    if (!tupleRepr->isParenType())
-      break;
-    nestedRepr = tupleRepr->getElementType(0);
-  }
+  auto *nestedRepr = typeRepr->getWithoutParens();
 
   if (auto isolated = dyn_cast<IsolatedTypeRepr>(nestedRepr))
     nestedRepr = isolated->getBase();

lib/Sema/TypeCheckType.cpp

@@ -2834,15 +2834,9 @@ TypeResolver::resolveASTFunctionTypeParams(TupleTypeRepr *inputRepr,
 
     ValueOwnership ownership = ValueOwnership::Default;
 
-    auto *nestedRepr = eltTypeRepr;
-
     // Look through parens here; other than parens, specifiers
     // must appear at the top level of a parameter type.
-    while (auto *tupleRepr = dyn_cast<TupleTypeRepr>(nestedRepr)) {
-      if (!tupleRepr->isParenType())
-        break;
-      nestedRepr = tupleRepr->getElementType(0);
-    }
+    auto *nestedRepr = eltTypeRepr->getWithoutParens();
 
     bool isolated = false;
     bool compileTimeConst = false;