Fix bug parsing second optional call expression with type arguments i…

…n chain

Summary:
Hermes currently has a bug when parsing optional chains that contain two optional calls that both have type arguments.

This is because `parseCallExpression` maintains a `typeArgs` variable when looping through parts of an optional chain that is filled with type args when a call expression with type arguments is encountered. However this is not being reset to null for optional call expressions, meaning the next optional call expression that is encountered will notice that `typeArgs` is non-null and then enter a bad state when it tries to parse its own type arguments. This results in the second optional call with type arguments actually being parsed as an optional member that is part of two comparisons (due to the `<` and `>`).

The fix for this is simply that we need to clear the `typeArgs` variable after optional call expressions are parsed.

Reviewed By: avp

Differential Revision: D24550737

fbshipit-source-id: 0e6dc65e0ae4ac9ac20a78d39085b6933189bb5d

lib/Parser/JSParserImpl.cpp

@@ -3253,10 +3253,11 @@ Optional<ESTree::Node *> JSParserImpl::parseCallExpression(
             debugLoc,
             new (context_)
                 ESTree::CallExpressionNode(expr, typeArgs, std::move(argList)));
-        // typeArgs have been used, discard them so the next item in the call
-        // chain can populate them if necessary.
-        typeArgs = nullptr;
       }
+
+      // typeArgs have been used, discard them so the next item in the call
+      // chain can populate them if necessary.
+      typeArgs = nullptr;
     } else if (checkN(
                    TokenKind::l_square,
                    TokenKind::period,

test/Parser/flow/optional-chaining.js

@@ -0,0 +1,101 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: %hermes -dump-ast -parse-flow --pretty-json %s | %FileCheck %s --match-full-lines
+
+// CHECK: {
+// CHECK-NEXT:   "type": "Program",
+// CHECK-NEXT:   "body": [
+
+a?.b<string>();
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "type": "ExpressionStatement",
+// CHECK-NEXT:       "expression": {
+// CHECK-NEXT:         "type": "OptionalCallExpression",
+// CHECK-NEXT:         "callee": {
+// CHECK-NEXT:           "type": "OptionalMemberExpression",
+// CHECK-NEXT:           "object": {
+// CHECK-NEXT:             "type": "Identifier",
+// CHECK-NEXT:             "name": "a"
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "property": {
+// CHECK-NEXT:             "type": "Identifier",
+// CHECK-NEXT:             "name": "b"
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "computed": false,
+// CHECK-NEXT:           "optional": true
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "typeArguments": {
+// CHECK-NEXT:           "type": "TypeParameterInstantiation",
+// CHECK-NEXT:           "params": [
+// CHECK-NEXT:             {
+// CHECK-NEXT:               "type": "StringTypeAnnotation"
+// CHECK-NEXT:             }
+// CHECK-NEXT:           ]
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "arguments": [],
+// CHECK-NEXT:         "optional": false
+// CHECK-NEXT:       },
+// CHECK-NEXT:       "directive": null
+// CHECK-NEXT:     },
+
+a?.b<string>()?.c<string>();
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "type": "ExpressionStatement",
+// CHECK-NEXT:       "expression": {
+// CHECK-NEXT:         "type": "OptionalCallExpression",
+// CHECK-NEXT:         "callee": {
+// CHECK-NEXT:           "type": "OptionalMemberExpression",
+// CHECK-NEXT:           "object": {
+// CHECK-NEXT:             "type": "OptionalCallExpression",
+// CHECK-NEXT:             "callee": {
+// CHECK-NEXT:               "type": "OptionalMemberExpression",
+// CHECK-NEXT:               "object": {
+// CHECK-NEXT:                 "type": "Identifier",
+// CHECK-NEXT:                 "name": "a"
+// CHECK-NEXT:               },
+// CHECK-NEXT:               "property": {
+// CHECK-NEXT:                 "type": "Identifier",
+// CHECK-NEXT:                 "name": "b"
+// CHECK-NEXT:               },
+// CHECK-NEXT:               "computed": false,
+// CHECK-NEXT:               "optional": true
+// CHECK-NEXT:             },
+// CHECK-NEXT:             "typeArguments": {
+// CHECK-NEXT:               "type": "TypeParameterInstantiation",
+// CHECK-NEXT:               "params": [
+// CHECK-NEXT:                 {
+// CHECK-NEXT:                   "type": "StringTypeAnnotation"
+// CHECK-NEXT:                 }
+// CHECK-NEXT:               ]
+// CHECK-NEXT:             },
+// CHECK-NEXT:             "arguments": [],
+// CHECK-NEXT:             "optional": false
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "property": {
+// CHECK-NEXT:             "type": "Identifier",
+// CHECK-NEXT:             "name": "c"
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "computed": false,
+// CHECK-NEXT:           "optional": true
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "typeArguments": {
+// CHECK-NEXT:           "type": "TypeParameterInstantiation",
+// CHECK-NEXT:           "params": [
+// CHECK-NEXT:             {
+// CHECK-NEXT:               "type": "StringTypeAnnotation"
+// CHECK-NEXT:             }
+// CHECK-NEXT:           ]
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "arguments": [],
+// CHECK-NEXT:         "optional": false
+// CHECK-NEXT:       },
+// CHECK-NEXT:       "directive": null
+// CHECK-NEXT:     }
+
+// CHECK-NEXT:   ]
+// CHECK-NEXT: }