[interop][SwiftToCxx] do not support generics with requirements for now

Author: hyp

lib/PrintAsClang/PrintClangFunction.cpp

@@ -318,24 +318,32 @@ ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
     const AbstractFunctionDecl *FD, StringRef name, Type resultTy,
     FunctionSignatureKind kind, ArrayRef<AdditionalParam> additionalParams,
     FunctionSignatureModifiers modifiers) {
-  if (kind == FunctionSignatureKind::CxxInlineThunk && FD->isGeneric()) {
-    os << "template<";
-    llvm::interleaveComma(FD->getGenericParams()->getParams(), os,
-                          [&](const GenericTypeParamDecl *genericParam) {
-                            os << "class ";
-                            ClangSyntaxPrinter(os).printBaseName(genericParam);
-                          });
-    os << ">\n";
-    os << "requires ";
-    llvm::interleave(
-        FD->getGenericParams()->getParams(), os,
-        [&](const GenericTypeParamDecl *genericParam) {
-          os << "swift::isUsableInGenericContext<";
-          ClangSyntaxPrinter(os).printBaseName(genericParam);
-          os << ">";
-        },
-        " && ");
-    os << "\n";
+  if (FD->isGeneric()) {
+    auto Signature = FD->getGenericSignature();
+    auto Requirements = Signature.getRequirements();
+    // FIXME: Support generic requirements.
+    if (!Requirements.empty())
+      return ClangRepresentation::unsupported;
+    if (kind == FunctionSignatureKind::CxxInlineThunk) {
+      os << "template<";
+      llvm::interleaveComma(FD->getGenericParams()->getParams(), os,
+                            [&](const GenericTypeParamDecl *genericParam) {
+                              os << "class ";
+                              ClangSyntaxPrinter(os).printBaseName(
+                                  genericParam);
+                            });
+      os << ">\n";
+      os << "requires ";
+      llvm::interleave(
+          FD->getGenericParams()->getParams(), os,
+          [&](const GenericTypeParamDecl *genericParam) {
+            os << "swift::isUsableInGenericContext<";
+            ClangSyntaxPrinter(os).printBaseName(genericParam);
+            os << ">";
+          },
+          " && ");
+      os << "\n";
+    }
   }
   auto emittedModule = FD->getModuleContext();
   OutputLanguageMode outputLang = kind == FunctionSignatureKind::CFunctionProto

test/Interop/SwiftToCxx/generics/generic-function-in-cxx.swift

@@ -35,6 +35,12 @@ public func genericRet<T>(_ x: T) -> T {
     return x
 }
 
+public func genericRequirementProtocol<T: Hashable>(_ x: T) {
+}
+
+public func genericRequirementClass<T>(_ x: T) where T: TestClass {
+}
+
 public class TestClass {
     let field: Int
 
@@ -84,6 +90,8 @@ public func createTestSmallStruct(_ x: UInt32) -> TestSmallStruct {
 // CHECK-NEXT: SWIFT_EXTERN void $s9Functions10genericRetyxxlF(SWIFT_INDIRECT_RESULT void * _Nonnull, const void * _Nonnull x, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericRet(_:)
 // CHECK-NEXT: SWIFT_EXTERN void $s9Functions11genericSwapyyxz_xztlF(void * _Nonnull x, void * _Nonnull y, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericSwap(_:_:)
 
+// CHECK-NOT: genericRequirement
+
 // Skip templates in impl classes.
 // CHECK: _impl_TestSmallStruct
 // CHECK:      template<class T>