Error when proc macro derive output cannot be fully parsed.

Author: m-ou-se

compiler/rustc_expand/src/proc_macro.rs

@@ -133,8 +133,11 @@ impl MultiItemModifier for ProcMacroDerive {
             }
         }
 
-        // fail if there have been errors emitted
-        if ecx.sess.parse_sess.span_diagnostic.err_count() > error_count_before {
+        // fail if there have been errors emitted,
+        // or if there's any unparsed tokens left.
+        if parser.token != token::Eof
+            || ecx.sess.parse_sess.span_diagnostic.err_count() > error_count_before
+        {
             ecx.struct_span_err(span, "proc-macro derive produced unparseable tokens").emit();
         }