fix #29530, field metadata generation

pkg/dev_compiler/lib/src/compiler/code_generator.dart

Index: pkg/dev_compiler/lib/src/compiler/code_generator.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/code_generator.dart b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
index 68bea1e3c384c9f4a192abfdf5054a883935db71..dfdf537bc85e95d31de7498359ccb17f1e9aabf6 100644
--- a/pkg/dev_compiler/lib/src/compiler/code_generator.dart
+++ b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
@@ -2958,7 +2958,7 @@ class CodeGenerator extends Object
       args.add(new JS.ArrayInitializer(
           metadata.map(_instantiateAnnotation).toList()));
     }
-    return _callHelper(isFinal ? 'finalFieldType(#)' : 'fieldType(#)', args);
+    return _callHelper(isFinal ? 'finalFieldType(#)' : 'fieldType(#)', [args]);
   }
 
   JS.ArrayInitializer _emitTypeNames(