Merge pull request #69515 from hyp/eng/generic-generic-generic-generic

[interop][SwiftToCxx] ensure Swift generic types can be used as template parameters to other Swift generic types in C++

Author: hyp

lib/PrintAsClang/PrintClangValueType.cpp

@@ -581,14 +581,27 @@ void ClangValueTypePrinter::printTypePrecedingGenericTraits(
 
   os << "#pragma clang diagnostic push\n";
   os << "#pragma clang diagnostic ignored \"-Wc++17-extensions\"\n";
-  if (!typeDecl->isGeneric()) {
-    // FIXME: generic type support.
+
+  if (printer.printNominalTypeOutsideMemberDeclTemplateSpecifiers(typeDecl))
     os << "template<>\n";
-    os << "static inline const constexpr bool isUsableInGenericContext<";
-    printer.printNominalTypeReference(typeDecl,
-                                      /*moduleContext=*/nullptr);
-    os << "> = true;\n";
-  }
+  os << "static inline const constexpr bool isUsableInGenericContext<";
+  printer.printNominalTypeReference(typeDecl,
+                                    /*moduleContext=*/nullptr);
+  os << "> = ";
+  if (typeDecl->isGeneric()) {
+    auto signature = typeDecl->getGenericSignature().getCanonicalSignature();
+    llvm::interleave(
+        signature.getInnermostGenericParams(), os,
+        [&](const GenericTypeParamType *genericParamType) {
+          os << "isUsableInGenericContext<";
+          printer.printGenericTypeParamTypeName(genericParamType);
+          os << '>';
+        },
+        " && ");
+  } else
+    os << "true";
+  os << ";\n";
+
   os << "#pragma clang diagnostic pop\n";
   os << "} // namespace swift\n";
   os << "\n";

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

@@ -95,6 +95,12 @@ public func inoutConcreteOpt(_ x: inout GenericOpt<UInt16>) {
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class SWIFT_SYMBOL("s:8Generics10GenericOptO") GenericOpt;
 
+// CHECK: template<class T_0_0>
+// CHECK-NEXT: #ifdef __cpp_concepts
+// CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0>
+// CHECK-NEXT: #endif
+// CHECK-NEXT: static inline const constexpr bool isUsableInGenericContext<Generics::GenericOpt<T_0_0>> = isUsableInGenericContext<T_0_0>;
+
 // CHECK: template<class T_0_0>
 // CHECK-NEXT: #ifdef __cpp_concepts
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0>

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

@@ -206,6 +206,12 @@ public func inoutConcretePair(_ x: UInt16, _ y: inout GenericPair<UInt16, UInt16
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class SWIFT_SYMBOL("s:8Generics11GenericPairV") GenericPair;
 
+// CHECK: template<class T_0_0, class T_0_1>
+// CHECK-NEXT: #ifdef __cpp_concepts
+// CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0> && swift::isUsableInGenericContext<T_0_1>
+// CHECK-NEXT: #endif // __cpp_concepts
+// CHECK-NEXT: static inline const constexpr bool isUsableInGenericContext<Generics::GenericPair<T_0_0, T_0_1>> = isUsableInGenericContext<T_0_0> && isUsableInGenericContext<T_0_1>;
+
 // CHECK: template<class T_0_0, class T_0_1>
 // CHECK-NEXT: #ifdef __cpp_concepts
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0> && swift::isUsableInGenericContext<T_0_1>

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

@@ -76,6 +76,7 @@
 // CHECK-NEXT: #endif
 // CHECK-NEXT: class SWIFT_SYMBOL("s:8Generics11GenericPairV") GenericPair;
 
+// CHECK: template<class T_0_0, class T_0_1>
 // CHECK: template<class T_0_0, class T_0_1>
 // CHECK: template<class T_0_0, class T_0_1>
 // CHECK-NEXT: #ifdef __cpp_concepts

test/Interop/SwiftToCxx/stdlib/combination-of-stdlib-generics-in-cxx.swift

@@ -0,0 +1,13 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -typecheck %s -typecheck -module-name UseOptional -enable-experimental-cxx-interop -emit-clang-header-path %t/stdlib.h
+// RUN: %FileCheck %s < %t/stdlib.h
+
+// RUN: %check-interop-cxx-header-in-clang(-DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY %t/stdlib.h -Wno-unused-private-field -Wno-unused-function)
+
+@_expose(Cxx)
+public func testOptIntArray() -> [Int]? {
+    return []
+}
+
+// CHECK: SWIFT_INLINE_THUNK swift::Optional<swift::Array<swift::Int>> testOptIntArray()

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

@@ -22,6 +22,7 @@
 // CHECK-NEXT: class SWIFT_SYMBOL("s:Sa") Array;
 // CHECK: template<class T_0_0>
 // CHECK: template<class T_0_0>
+// CHECK: template<class T_0_0>
 // CHECK-NEXT: #ifdef __cpp_concepts
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0>
 // CHECK-NEXT: #endif