[cxx-interop] Class template specializations each need their own metadata.

lib/IRGen/GenMeta.cpp

@@ -1170,7 +1170,14 @@ namespace {
         // declaration's name as the ABI name.
       } else if (auto clangDecl =
                             Mangle::ASTMangler::getClangDeclForMangling(Type)) {
-        abiName = clangDecl->getName();
+        // Class template specializations need to use their mangled name so
+        // that each specialization gets its own metadata. A class template
+        // specialization's Swift name will always be the mangled name, so just
+        // use that.
+        if (auto spec = dyn_cast<clang::ClassTemplateSpecializationDecl>(clangDecl))
+          abiName = Type->getName().str();
+        else
+          abiName = clangDecl->getName();
 
         // Typedefs and compatibility aliases that have been promoted to
         // their own nominal types need to be marked specially.

test/Interop/Cxx/templates/dependent-types.swift

@@ -34,7 +34,7 @@ DependentTypesTestSuite.test("Multiple dependent arguments (inferred type).") {
 }
 
 DependentTypesTestSuite.test("Multiple dependent arguments (not inferred).") {
-  let m = multipleDependentArgs(M<Int>(value: 42), M<CInt>(value: 0), T: Int.self, U: Int.self) as! M<Int>
+  let m = multipleDependentArgs(M<Int>(value: 42), M<CInt>(value: 0), T: Int.self, U: CInt.self) as! M<Int>
   expectEqual(m.getValue(), 42)
 }
 

test/Interop/Cxx/value-witness-table/Inputs/class-template-metadata.h

@@ -0,0 +1,10 @@
+#ifndef TEST_INTEROP_CXX_VALUE_WITNESS_TABLE_INPUTS_CLASS_TEMPLATE_METADATA_H
+#define TEST_INTEROP_CXX_VALUE_WITNESS_TABLE_INPUTS_CLASS_TEMPLATE_METADATA_H
+
+template<class T>
+struct ClassTemplate {};
+
+using Spec1 = ClassTemplate<int>;
+using Spec2 = ClassTemplate<Spec1>;
+
+#endif // TEST_INTEROP_CXX_VALUE_WITNESS_TABLE_INPUTS_CLASS_TEMPLATE_METADATA_H

test/Interop/Cxx/value-witness-table/Inputs/module.modulemap

@@ -12,3 +12,8 @@ module CopyConstructors {
   header "copy-constructors.h"
   requires cplusplus
 }
+
+module ClassTemplateMetadata {
+  header "class-template-metadata.h"
+  requires cplusplus
+}

test/Interop/Cxx/value-witness-table/class-template-metadata.swift

@@ -0,0 +1,20 @@
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-cxx-interop)
+//
+// REQUIRES: executable_test
+
+import ClassTemplateMetadata
+import StdlibUnittest
+
+var ClassTemplateMetadataTestSuite = TestSuite("Class Template Metadata")
+
+func cmpMetadata<T, U>(_ _: T, _ _: U) -> Bool { "\(T.self)" == "\(U.self)" }
+
+ClassTemplateMetadataTestSuite.test("Different specializations of a class template have different metadata.") {
+  let a = Spec1()
+  let b = Spec2()
+
+  expectFalse(cmpMetadata(a, b))
+  expectTrue(cmpMetadata(a, a))
+}
+
+runAllTests()