[interop][SwiftToCxx] add static_assert type checking for generic types in pre-C++20 mode

Author: hyp

lib/PrintAsClang/PrintClangValueType.cpp

@@ -241,6 +241,9 @@ void ClangValueTypePrinter::printValueTypeDecl(
   ClangSyntaxPrinter(os).printBaseName(typeDecl);
   os << " final {\n";
   os << "public:\n";
+  if (genericSignature)
+    ClangSyntaxPrinter(os).printGenericSignatureInnerStaticAsserts(
+        *genericSignature);
 
   // Print out the destructor.
   os << "  inline ~";
@@ -373,6 +376,9 @@ void ClangValueTypePrinter::printValueTypeDecl(
         printCxxImplClassName(os, typeDecl);
         os << " {\n";
         os << "public:\n";
+        if (genericSignature)
+          ClangSyntaxPrinter(os).printGenericSignatureInnerStaticAsserts(
+              *genericSignature);
 
         os << "  static inline char * _Nonnull getOpaquePointer(";
         printCxxTypeName(os, typeDecl, moduleContext);

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

@@ -109,6 +109,9 @@ public func inoutConcreteOpt(_ x: inout GenericOpt<UInt16>) {
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class GenericOpt final {
 // CHECK-NEXT: public:
+// CHECK-NEXT: #ifndef __cpp_concepts
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_0>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: #endif
 // CHECK-NEXT: inline ~GenericOpt() {
 // CHECK-NEXT:   auto metadata = _impl::$s8Generics10GenericOptOMa(0, swift::TypeMetadataTrait<T_0_0>::getTypeMetadata());
 // CHECK-NEXT:   auto *vwTableAddr = reinterpret_cast<swift::_impl::ValueWitnessTable **>(metadata._0) - 1;

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

@@ -222,6 +222,10 @@ public func inoutConcretePair(_ x: UInt16, _ y: inout GenericPair<UInt16, UInt16
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class GenericPair final {
 // CHECK-NEXT: public:
+// CHECK-NEXT: #ifndef __cpp_concepts
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_0>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_1>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: #endif
 // CHECK-NEXT:   inline ~GenericPair() {
 // CHECK-NEXT:     auto metadata = _impl::$s8Generics11GenericPairVMa(0, swift::TypeMetadataTrait<T_0_0>::getTypeMetadata(), swift::TypeMetadataTrait<T_0_1>::getTypeMetadata());
 
@@ -235,6 +239,10 @@ public func inoutConcretePair(_ x: UInt16, _ y: inout GenericPair<UInt16, UInt16
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class _impl_GenericPair {
 // CHECK-NEXT: public:
+// CHECK-NEXT: #ifndef __cpp_concepts
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_0>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_1>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: #endif
 // CHECK-NEXT:   static inline char * _Nonnull getOpaquePointer(GenericPair<T_0_0, T_0_1> &object) { return object._getOpaquePointer(); }
 // CHECK-NEXT:   static inline const char * _Nonnull getOpaquePointer(const GenericPair<T_0_0, T_0_1> &object) { return object._getOpaquePointer(); }
 // CHECK-NEXT: template<class T>

test/Interop/SwiftToCxx/generics/generic-type-cxx-type-invalid.cpp

@@ -0,0 +1,18 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend %S/generic-struct-in-cxx.swift -typecheck -module-name Structs -clang-header-expose-decls=all-public -emit-clang-header-path %t/structs.h
+
+// RUN: %target-interop-build-clangxx -std=gnu++20 -c %s -I %t -o /dev/null -DUSE_TYPE=int
+// RUN: %target-interop-build-clangxx -std=gnu++17 -c %s -I %t -o /dev/null -DUSE_TYPE=int
+// RUN: not %target-interop-build-clangxx -std=gnu++20 -c %s -I %t -o /dev/null -DUSE_TYPE=CxxStruct
+// RUN: not %target-interop-build-clangxx -std=gnu++17 -c %s -I %t -o /dev/null -DUSE_TYPE=CxxStruct 2>&1 | %FileCheck -check-prefix=STATIC_ASSERT_ERROR %s
+
+#include "structs.h"
+
+struct CxxStruct { int x = 0; };
+
+bool test(Structs::GenericPair<USE_TYPE, USE_TYPE> &val) {
+  return sizeof(val) > 4;
+}
+
+// STATIC_ASSERT_ERROR: type cannot be used in a Swift generic context

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

@@ -28,6 +28,9 @@
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class Array final {
 // CHECK-NEXT: public:
+// CHECK-NEXT: #ifndef __cpp_concepts
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_0>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: #endif
 // CHECK-NEXT: inline ~Array() {
 // CHECK: }
 // CHECK-NEXT: inline Array(const Array &other) {
@@ -49,6 +52,9 @@
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class Optional final {
 // CHECK-NEXT: public:
+// CHECK-NEXT: #ifndef __cpp_concepts
+// CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_0>, "type cannot be used in a Swift generic context");
+// CHECK-NEXT: #endif
 // CHECK-NEXT: inline ~Optional() {
 // CHECK: }
 // CHECK-NEXT: inline Optional(const Optional &other) {