fix(build): Remove ambiguity in service method call (#327)

When calling methods on Arc<MyService> where the method is also defined on Arc (e.g. drop and clone), calling inner.#method_ident(request) will actually attempt to call the Arc method instead of the method on the service, resulting in a compile error. This change removes the ambiguity by dereferencing the inner Arc.

tests/ambiguous_methods/proto/ambiguous_methods.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+package ambiguous_methods;
+
+message DropReq {}
+message DropResp {}
+
+// The generated stubs can confuse drop and clone
+// with the same method names from Arc,
+// resulting in a compile error.
+service HelloService {
+    rpc Drop (DropReq) returns (DropResp);
+    rpc Clone (DropReq) returns (DropResp);
+}
+
+service HelloStreamingService {
+    rpc Drop (DropReq) returns (stream DropResp);
+    rpc Clone (DropReq) returns (stream DropResp);
+}