[interop][SwiftToCxx] add a testcase for generic struct passthrough

Author: hyp

test/Interop/SwiftToCxx/generics/generic-struct-execution.cpp

@@ -19,5 +19,10 @@ int main() {
   auto x = makeGenericPair<int, int>(11, 42);
   takeGenericPair(x);
 // CHECK: GenericPair<Int32, Int32>(x: 11, y: 42)
+  auto xprime = passThroughGenericPair(x, -995);
+  takeGenericPair(x);
+  takeGenericPair(xprime);
+// CHECK-NEXT: GenericPair<Int32, Int32>(x: 11, y: 42)
+// CHECK-NEXT: GenericPair<Int32, Int32>(x: 11, y: -995)
   return 0;
 }

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

@@ -25,11 +25,15 @@ public func takeGenericPair<T, T1>(_ x: GenericPair<T, T1>) {
     print(x)
 }
 
+public func passThroughGenericPair<T1, T>(_ x: GenericPair<T1, T>, _ y: T)  -> GenericPair<T1, T> {
+    return GenericPair<T1, T>(x: x.x, y: y)
+}
+
 // CHECK: template<class T_0_0, class T_0_1>
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0> && swift::isUsableInGenericContext<T_0_1>
 // CHECK-NEXT: class _impl_GenericPair;
 // CHECK-EMPTY:
-// CHECK-NEXT: static_assert(2 <= 3, "unsupported generic requirement list for metadata func"); 
+// CHECK-NEXT: static_assert(2 <= 3, "unsupported generic requirement list for metadata func");
 // CHECK-NEXT: // Type metadata accessor for GenericPair
 // CHECK-NEXT: SWIFT_EXTERN swift::_impl::MetadataResponseTy $s8Generics11GenericPairVMa(swift::_impl::MetadataRequestTy, void * _Nonnull, void * _Nonnull) SWIFT_NOEXCEPT SWIFT_CALL;
 
@@ -69,6 +73,14 @@ public func takeGenericPair<T, T1>(_ x: GenericPair<T, T1>) {
 // CHECK-NEXT:   });
 // CHECK-NEXT: }
 
+// CHECK: template<class T1, class T>
+// CHECK-NEXT: requires swift::isUsableInGenericContext<T1> && swift::isUsableInGenericContext<T>
+// CHECK-NEXT: inline GenericPair<T1, T> passThroughGenericPair(const GenericPair<T1, T>& x, const T & y) noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK-NEXT:   return _impl::_impl_GenericPair<T1, T>::returnNewValue([&](void * _Nonnull result) {
+// CHECK-NEXT:     _impl::$s8Generics22passThroughGenericPairyAA0dE0Vyxq_GAE_q_tr0_lF(result, _impl::_impl_GenericPair<T1, T>::getOpaquePointer(x), swift::_impl::getOpaquePointer(y), swift::getTypeMetadata<T1>(), swift::getTypeMetadata<T>());
+// CHECK-NEXT:   });
+// CHECK-NEXT: }
+
 // CHECK: template<class T, class T1>
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T> && swift::isUsableInGenericContext<T1>
 // CHECK-NEXT: inline void takeGenericPair(const GenericPair<T, T1>& x) noexcept {