[interop][SwiftToCxx] avoid -Wshadow warning for C++ representation of enum member parameters

lib/PrintAsClang/PrintClangFunction.cpp

@@ -639,6 +639,25 @@ static void printDirectReturnOrParamCType(
   });
 }
 
+/// Make adjustments to the Swift parameter name in generated C++, to
+/// avoid things like additional warnings.
+static void renameCxxParameterIfNeeded(const AbstractFunctionDecl *FD,
+                                       std::string &paramName) {
+  if (paramName.empty())
+    return;
+  const auto *enumDecl = FD->getDeclContext()->getSelfEnumDecl();
+  if (!enumDecl)
+    return;
+  // Rename a parameter in an enum method that shadows an existing case name,
+  // to avoid a -Wshadow warning in Clang.
+  for (const auto *Case : enumDecl->getAllElements()) {
+    if (Case->getNameStr() == paramName) {
+      paramName = (llvm::Twine(paramName) + "_").str();
+      return;
+    }
+  }
+}
+
 ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
     const AbstractFunctionDecl *FD, const LoweredFunctionSignature &signature,
     StringRef name, Type resultTy, FunctionSignatureKind kind,
@@ -895,6 +914,7 @@ ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
               param, param->getInterfaceType());
       std::string paramName =
           param->getName().empty() ? "" : param->getName().str().str();
+      renameCxxParameterIfNeeded(FD, paramName);
       // Always emit a named parameter for the C++ inline thunk to ensure it
       // can be referenced in the body.
       if (kind == FunctionSignatureKind::CxxInlineThunk && paramName.empty()) {
@@ -1113,6 +1133,7 @@ void DeclAndTypeClangFunctionPrinter::printCxxThunkBody(
         paramOS << "_" << paramIndex;
       } else {
         paramName = param.getName().str().str();
+        renameCxxParameterIfNeeded(FD, paramName);
       }
       ++paramIndex;
       printCxxToCFunctionParameterUse(param.getInterfaceType(), paramName,

lib/PrintAsClang/_SwiftStdlibCxxOverlay.h

@@ -81,8 +81,7 @@ public:
   using Index =
       decltype(reinterpret_cast<Collection *>(0x123)->getStartIndex());
 
-  SWIFT_INLINE_THUNK CollectionIterator(const Collection &collection)
+  SWIFT_INLINE_THUNK CollectionIterator(const Collection &c) : collection(c) {
-      : collection(collection) {
     index = collection.getStartIndex();
     endIndex = collection.getEndIndex();
     // FIXME: Begin read access.

test/Interop/SwiftToCxx/enums/enum-member-param-no-shadow-case.swift

@@ -0,0 +1,31 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -typecheck -module-name Enums -clang-header-expose-decls=all-public -emit-clang-header-path %t/enums.h
+// RUN: %FileCheck %s < %t/enums.h
+
+// RUN: %check-interop-cxx-header-in-clang(%t/enums.h -Wno-unused-private-field -Wno-unused-function)
+
+public enum E {
+    case a
+    case b(Int)
+
+    public init(_ b: Int) {
+        self = .b(b)
+    }
+
+    public func takeParamA(_ a: Int) {}
+
+    public static func takeParamB(_ b: Int) {}
+}
+
+// CHECK: static inline E init(swift::Int b_)
+// CHECK: inline void takeParamA(swift::Int a_)
+// CHECK: static inline void takeParamB(swift::Int b_)
+
+// CHECK: E E::init(swift::Int b_) {
+// CHECK: _impl::$s5Enums1EOyACSicfC(b_)
+
+// CHECK: void E::takeParamA(swift::Int a_) const {
+// CHECK: _impl::$s5Enums1EO10takeParamAyySiF(a_,
+
+// CHECK: void E::takeParamB(swift::Int b_) {
+// CHECK: return _impl::$s5Enums1EO10takeParamByySiFZ(b_);

test/Interop/SwiftToCxx/functions/swift-functions-errors.swift

@@ -2,7 +2,7 @@
 // RUN: %target-swift-frontend %s -typecheck -module-name Functions -enable-experimental-cxx-interop -emit-clang-header-path %t/functions.h
 // RUN: %FileCheck %s < %t/functions.h
 
-// RUN: %check-interop-cxx-header-in-clang(%t/functions.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY  -Wno-shadow -Wno-unused-function)
+// RUN: %check-interop-cxx-header-in-clang(%t/functions.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-function)
 
 // CHECK-LABEL: namespace Functions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Functions") {
 

test/Interop/SwiftToCxx/stdlib/stdlib-dep-inline-in-cxx.swift

@@ -7,7 +7,7 @@
 
 // RUN: cat %t/stdlib.h %t/stdlib2.h > %t/two_includes.h
 
-// RUN: %check-interop-cxx-header-in-clang(-DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY %t/two_includes.h -Wno-unused-private-field -Wno-unused-function -Wno-shadow)
+// RUN: %check-interop-cxx-header-in-clang(-DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY %t/two_includes.h -Wno-unused-private-field -Wno-unused-function)
 
 @_expose(Cxx)
 public func test() -> String {

test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift

@@ -2,9 +2,7 @@
 // RUN: %target-swift-frontend -parse-as-library %platform-module-dir/Swift.swiftmodule/%module-target-triple.swiftinterface -enable-library-evolution -disable-objc-attr-requires-foundation-module -typecheck -module-name Swift -parse-stdlib -enable-experimental-cxx-interop -emit-clang-header-path %t/Swift.h  -experimental-skip-all-function-bodies
 // RUN: %FileCheck %s < %t/Swift.h
 
-// RUN: %check-interop-cxx-header-in-clang(%t/Swift.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-private-field -Wno-unused-function -Wno-shadow)
+// RUN: %check-interop-cxx-header-in-clang(%t/Swift.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-private-field -Wno-unused-function)
-
-// FIXME: remove need for -Wno-shadow
 
 // CHECK: namespace Swift __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Swift") {