Use ExpressionClassifier to identify valid arrow function formals

test/cctest/test-parsing.cc

Index: test/cctest/test-parsing.cc
diff --git a/test/cctest/test-parsing.cc b/test/cctest/test-parsing.cc
index f0abbc958f9a241f2270bc85864db9561817c34b..c6dd4740e3c565154f813fe728ef735b2e67dab7 100644
--- a/test/cctest/test-parsing.cc
+++ b/test/cctest/test-parsing.cc
@@ -3563,6 +3563,10 @@ TEST(ErrorsArrowFunctions) {
     "(foo ? bar : baz) => {}",
     "(a, foo ? bar : baz) => {}",
     "(foo ? bar : baz, a) => {}",
+    "(a.b, c) => {}",
+    "(c, a.b) => {}",
+    "(a['b'], c) => {}",
+    "(c, a['b']) => {}",
     NULL
   };