message: Only attempt to get field definition on object or interface type
  Fixes
diff: @@ -302,6 +302,7 @@ export class Compiler {
  field.isConditional = true;
  }
  + if (parentType instanceof GraphQLObjectType || parentType instanceof GraphQLInterfaceType) {
  const fieldDef = parentType.getFields()[fieldName];
  if (fieldDef) {
  const description = fieldDef.description;
  @@ -314,6 +315,7 @@ export class Compiler {
  deprecationReason: fieldDef.deprecationReason,
  });
  }
  + }
  const bareType = getNamedType(type);
  