Disallow 'yield' in async arrow parameter lists inside generators

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 7d011cac962d1a4ccaa8ba679ac13ec597df48c3..b4ef374356e2843c8e30671ebdc7c1cf877f1324 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -2897,6 +2897,7 @@ ParserBase<Impl>::ParseLeftHandSideExpression(ExpressionClassifier* classifier,
               fni_->RemoveAsyncKeywordFromEnd();
             }
             ValidateBindingPattern(&async_classifier, CHECK_OK);
+            ValidateFormalParameterInitializer(&async_classifier, CHECK_OK);
             if (!async_classifier.is_valid_async_arrow_formal_parameters()) {
               ReportClassifierError(
                   async_classifier.async_arrow_formal_parameters_error());