THRIFT-4953: Missing Field Identifiers

When identifiers are not specified, negative id will be converted to a valid
rust identifier.
diff --git a/lib/rs/test/Makefile.am b/lib/rs/test/Makefile.am
index 8edd756..486188c 100644
--- a/lib/rs/test/Makefile.am
+++ b/lib/rs/test/Makefile.am
@@ -25,6 +25,7 @@
 	$(THRIFT) -I ./thrifts -out src --gen rs thrifts/Midlayer.thrift
 	$(THRIFT) -I ./thrifts -out src --gen rs thrifts/Ultimate.thrift
 	$(THRIFT) -out src --gen rs $(top_builddir)/test/Recursive.thrift
+	$(THRIFT) -out src --gen rs $(top_builddir)/test/Identifiers.thrift #THRIFT-4953
 
 check: stubs
 	$(CARGO) build