add message interfaces

lspgenerator/go/base_types.py

@@ -110,7 +110,7 @@ def generate_base_types(
 		),
 	)
 	result.append(
-		"\n".join(
+		join(
 			[
 				"type ResponseError struct {",
 				'\tCode int32 `json:"code"`',
@@ -120,5 +120,23 @@ def generate_base_types(
 			],
 		),
 	)
+	result.append(
+		join(
+			[
+				"type Message interface {",
+				"	isMessage()",
+				"}",
+				"type Request interface {",
+				"	isRequest()",
+				"}",
+				"type Notification interface {",
+				"	isNotification()",
+				"}",
+				"type Response interface {",
+				"	isResponse()",
+				"}",
+			],
+		),
+	)
 	result.append("\n")
 	return result

lspgenerator/go/notifications.py

@@ -46,6 +46,10 @@ def generate_notifications(
 			f'\tParams {param_type} `json:"params"`',
 		]
 		struct.append("}")
+		struct.append(f"func (t *{notification.typeName}) isMessage() {{}}")
+		struct.append(
+			f"func (t *{notification.typeName}) isNotification() {{}}"
+		)
 		struct += [
 			f"func (t *{notification.typeName}) UnmarshalJSON(x []byte) error {{",
 			"   var m map[string]any",

lspgenerator/go/requests.py

@@ -50,6 +50,8 @@ def generate_requests(
 		]
 
 		struct.append("}")
+		struct.append(f"func (t *{request.typeName}) isMessage() {{}}")
+		struct.append(f"func (t *{request.typeName}) isRequest() {{}}")
 		struct += [
 			f"func (t *{request.typeName}) UnmarshalJSON(x []byte) error {{",
 			"   var m map[string]any",
@@ -117,5 +119,7 @@ def generate_requests(
 			"   return nil",
 			"}",
 		]
+		struct.append(f"func (t *{response_name}) isMessage() {{}}")
+		struct.append(f"func (t *{response_name}) isResponse() {{}}")
 		result.append(join(struct))
 	return result

protocol/interfaces_test.go

@@ -0,0 +1,11 @@
+package protocol
+
+// Compile-time interface compliance checks
+var (
+	_ Message      = (*InitializeRequest)(nil)
+	_ Message      = (*InitializedNotification)(nil)
+	_ Message      = (*InitializeResponse)(nil)
+	_ Request      = (*InitializeRequest)(nil)
+	_ Notification = (*InitializedNotification)(nil)
+	_ Response     = (*InitializeResponse)(nil)
+)