[Cpp Parser] Support Template Partial Specialization

cpp/libclang/integration_test/cases/template_partial_specialization_ids/BUILD

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+# *******************************************************************************
+# Copyright (c) 2026 Contributors to the Eclipse Foundation
+#
+# See the NOTICE file(s) distributed with this work for additional
+# information regarding copyright ownership.
+#
+# This program and the accompanying materials are made available under the
+# terms of the Apache License Version 2.0 which is available at
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# SPDX-License-Identifier: Apache-2.0
+# *******************************************************************************
+load("//cpp/libclang/integration_test:test_rules.bzl", "cpp_parser_integration_test")
+
+cc_library(
+    name = "template_partial_specialization_ids",
+    srcs = ["specialization.cpp"],
+    hdrs = [
+        "specialization.h",
+        "specialization_with_return.h",
+        "specialization_without_return.h",
+    ],
+    visibility = ["//cpp/libclang:__subpackages__"],
+)
+
+cpp_parser_integration_test(
+    name = "test_template_partial_specialization_ids",
+    expected_output = ["expected.json"],
+    target = ":template_partial_specialization_ids",
+)

cpp/libclang/integration_test/cases/template_partial_specialization_ids/expected.json

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+{
+  "functions": [],
+  "types": {
+    "demo::Endpoint<ReturnType (ArgTypes...)>": {
+      "enclosing_namespace_id": "demo",
+      "entity_type": "Class",
+      "enum_literals": [],
+      "id": "demo::Endpoint<ReturnType (ArgTypes...)>",
+      "methods": [
+        {
+          "modifiers": [],
+          "name": "Request",
+          "parameters": [
+            {
+              "is_pack_expansion": true,
+              "is_variadic": false,
+              "name": "args",
+              "param_type": "const ArgTypes &"
+            }
+          ],
+          "return_type": "ReturnType",
+          "template_parameters": null,
+          "visibility": "public",
+          "source_location": {
+            "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_with_return.h",
+            "line": 28
+          }
+        }
+      ],
+      "name": "Endpoint",
+      "relationships": [],
+      "source_location": {
+        "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_with_return.h",
+        "line": 25
+      },
+      "template_parameters": [
+        {
+          "Type": {
+            "is_pack": false,
+            "name": "ReturnType"
+          }
+        },
+        {
+          "Type": {
+            "is_pack": true,
+            "name": "ArgTypes"
+          }
+        }
+      ],
+      "type_aliases": [],
+      "variables": [
+        {
+          "data_type": "int",
+          "is_static": false,
+          "name": "parameter_count_",
+          "source_location": {
+            "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_with_return.h",
+            "line": 31
+          },
+          "visibility": "private"
+        }
+      ]
+    },
+    "demo::Endpoint<void (ArgTypes...)>": {
+      "enclosing_namespace_id": "demo",
+      "entity_type": "Class",
+      "enum_literals": [],
+      "id": "demo::Endpoint<void (ArgTypes...)>",
+      "methods": [
+        {
+          "modifiers": [],
+          "name": "Notify",
+          "parameters": [
+            {
+              "is_pack_expansion": true,
+              "is_variadic": false,
+              "name": "args",
+              "param_type": "const ArgTypes &"
+            }
+          ],
+          "return_type": "void",
+          "template_parameters": null,
+          "visibility": "public",
+          "source_location": {
+            "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_without_return.h",
+            "line": 28
+          }
+        }
+      ],
+      "name": "Endpoint",
+      "relationships": [],
+      "source_location": {
+        "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_without_return.h",
+        "line": 25
+      },
+      "template_parameters": [
+        {
+          "Type": {
+            "is_pack": true,
+            "name": "ArgTypes"
+          }
+        }
+      ],
+      "type_aliases": [],
+      "variables": [
+        {
+          "data_type": "int",
+          "is_static": false,
+          "name": "notification_count_",
+          "source_location": {
+            "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_without_return.h",
+            "line": 31
+          },
+          "visibility": "private"
+        }
+      ]
+    },
+    "demo::Endpoint": {
+      "enclosing_namespace_id": "demo",
+      "entity_type": "Class",
+      "enum_literals": [],
+      "id": "demo::Endpoint",
+      "methods": [],
+      "name": "Endpoint",
+      "relationships": [],
+      "source_location": {
+        "file": "./cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization.h",
+        "line": 23
+      },
+      "template_parameters": [
+        {
+          "Type": {
+            "is_pack": false,
+            "name": "Signature"
+          }
+        }
+      ],
+      "type_aliases": [],
+      "variables": []
+    }
+  }
+}

cpp/libclang/integration_test/cases/template_partial_specialization_ids/run_test.rs

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+// *******************************************************************************
+// Copyright (c) 2026 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Apache License Version 2.0 which is available at
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// SPDX-License-Identifier: Apache-2.0
+// *******************************************************************************
+
+use test_framework::run_parser_case;
+
+#[test]
+fn test_template_partial_specialization_ids() {
+    run_parser_case();
+}

cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization.cpp

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+/********************************************************************************
+ * Copyright (c) 2026 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+
+#include "specialization_with_return.h"
+#include "specialization_without_return.h"

cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization.h

@@ -0,0 +1,30 @@
+/********************************************************************************
+ * Copyright (c) 2026 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+
+#ifndef CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_H
+#define CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_H
+
+namespace demo
+{
+
+// Primary template kept in its own header so the parser has to merge it with
+// function-signature partial specializations declared elsewhere.
+template <typename Signature>
+class Endpoint
+{
+	static_assert(sizeof(Signature) == 0, "Endpoint only supports function-signature template arguments.");
+};
+
+}  // namespace demo
+
+#endif  // CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_H

cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_with_return.h

@@ -0,0 +1,36 @@
+/********************************************************************************
+ * Copyright (c) 2026 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+
+#ifndef CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_WITH_RETURN_H
+#define CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_WITH_RETURN_H
+
+#include "specialization.h"
+
+namespace demo
+{
+
+// Covers a partial specialization that binds both a regular template parameter
+// and a parameter pack from a function-signature template argument.
+template <typename ReturnType, typename... ArgTypes>
+class Endpoint<ReturnType(ArgTypes...)>
+{
+  public:
+    ReturnType Request(const ArgTypes&... args);
+
+  private:
+    int parameter_count_;
+};
+
+}  // namespace demo
+
+#endif  // CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_WITH_RETURN_H

cpp/libclang/integration_test/cases/template_partial_specialization_ids/specialization_without_return.h

@@ -0,0 +1,36 @@
+/********************************************************************************
+ * Copyright (c) 2026 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+
+#ifndef CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_WITHOUT_RETURN_H
+#define CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_WITHOUT_RETURN_H
+
+#include "specialization.h"
+
+namespace demo
+{
+
+// Mirrors the void-return specialization pattern used by ProxyMethod and keeps
+// the parameter pack in the specialization itself.
+template <typename... ArgTypes>
+class Endpoint<void(ArgTypes...)>
+{
+  public:
+    void Notify(const ArgTypes&... args);
+
+  private:
+    int notification_count_;
+};
+
+}  // namespace demo
+
+#endif  // CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_IDS_SPECIALIZATION_WITHOUT_RETURN_H

cpp/libclang/integration_test/cases/template_partial_specialization_relationship_target/BUILD

@@ -0,0 +1,30 @@
+# *******************************************************************************
+# Copyright (c) 2026 Contributors to the Eclipse Foundation
+#
+# See the NOTICE file(s) distributed with this work for additional
+# information regarding copyright ownership.
+#
+# This program and the accompanying materials are made available under the
+# terms of the Apache License Version 2.0 which is available at
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# SPDX-License-Identifier: Apache-2.0
+# *******************************************************************************
+load("//cpp/libclang/integration_test:test_rules.bzl", "cpp_parser_integration_test")
+
+cc_library(
+    name = "template_partial_specialization_relationship_target",
+    srcs = ["relationship.cpp"],
+    hdrs = [
+        "endpoint.h",
+        "endpoint_without_return.h",
+        "holder.h",
+    ],
+    visibility = ["//cpp/libclang:__subpackages__"],
+)
+
+cpp_parser_integration_test(
+    name = "test_template_partial_specialization_relationship_target",
+    expected_output = ["expected.json"],
+    target = ":template_partial_specialization_relationship_target",
+)

cpp/libclang/integration_test/cases/template_partial_specialization_relationship_target/endpoint.h

@@ -0,0 +1,30 @@
+/********************************************************************************
+ * Copyright (c) 2026 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+
+#ifndef CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_RELATIONSHIP_TARGET_ENDPOINT_H
+#define CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_RELATIONSHIP_TARGET_ENDPOINT_H
+
+namespace demo
+{
+
+// Primary template exists as a distinct entity, and the relationship logic
+// currently prefers this template base over a concrete specialization target.
+template <typename Signature>
+class Endpoint
+{
+    static_assert(sizeof(Signature) == 0, "Endpoint only supports function-signature template arguments.");
+};
+
+}  // namespace demo
+
+#endif  // CPP_LIBCLANG_INTEGRATION_TEST_CASES_TEMPLATE_PARTIAL_SPECIALIZATION_RELATIONSHIP_TARGET_ENDPOINT_H