From cda02aefcad60575dc3d1f474177a986ffdb917e Mon Sep 17 00:00:00 2001
From: Mike Pennisi <mike@mikepennisi.com>
Date: Sat, 24 Jun 2017 16:07:21 -0400
Subject: [PATCH] [[FIX]] Correct invalid function invocation

The second parameter of the `expression` function accepts a value that
modifies how the next token is parsed. When set to `true`, the token is
interpreted as the beginning of a statement; otherwise, it is
interpreted as the beginning of an expression.

Two call sites within the `for` statement's parsing logic specified the
string value `"for"`. Due to inconsistencies in how the parameter was
interpreted internally, this causes `expression` to mix parsing
strategies. Specifically:

- It used the "statement" parsing strategy to mark the token value as
  beginning a statement. This could be observed in the application of
  the `singleGroups` linting option. Further, it disqualify it for
  consideration as a Mozilla "let expression"
- It used the "expression" parsing strategy to ignore the token's `fud`
  method

Since the grammar does not allow a statement in either location, the
"expression" parsing strategy should be used consistently.

Achieve this by removing the argument from the call site, thereby
falling back to the default behavior of the `expression` function.
Update `expression` to consistently interpret the parameter for
"truthiness" in order to discourage similar ambiguity in the future.
---
 src/jshint.js         |  6 +++---
 tests/unit/options.js | 12 ++++++++++--
 tests/unit/parser.js  |  8 ++++++--
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/jshint.js b/src/jshint.js
index 9ffda3e033..9f9493d388 100644
--- a/src/jshint.js
+++ b/src/jshint.js
@@ -924,7 +924,7 @@ var JSHINT = (function() {
       state.tokens.curr.beginsStmt = true;
     }
 
-    if (initial === true && state.tokens.curr.fud) {
+    if (initial && state.tokens.curr.fud) {
       left = state.tokens.curr.fud();
     } else {
       if (state.tokens.curr.nud) {
@@ -4514,7 +4514,7 @@ var JSHINT = (function() {
           state.tokens.curr.fud();
         } else {
           for (;;) {
-            expression(0, "for");
+            expression(0);
             if (state.tokens.next.id !== ",") {
               break;
             }
@@ -4538,7 +4538,7 @@ var JSHINT = (function() {
       }
       if (state.tokens.next.id !== ")") {
         for (;;) {
-          expression(0, "for");
+          expression(0);
           if (state.tokens.next.id !== ",") {
             break;
           }
diff --git a/tests/unit/options.js b/tests/unit/options.js
index 5fce47b755..d81d34ca84 100644
--- a/tests/unit/options.js
+++ b/tests/unit/options.js
@@ -3330,13 +3330,17 @@ singleGroups.objectLiterals = function (test) {
     // Invalid forms
     "var a = ({}).method();",
     "if (({}).method()) {}",
-    "var b = { a: ({}).method() };"
+    "var b = { a: ({}).method() };",
+    "for (({}); ;) {}",
+    "for (; ;({})) {}"
   ];
 
   TestRun(test, "grouping operator not required")
     .addError(4, 9, "Unnecessary grouping operator.")
     .addError(5, 5, "Unnecessary grouping operator.")
     .addError(6, 14, "Unnecessary grouping operator.")
+    .addError(7, 6, "Unnecessary grouping operator.")
+    .addError(8, 9, "Unnecessary grouping operator.")
     .test(code, { singleGroups: true });
 
   test.done();
@@ -3458,13 +3462,17 @@ singleGroups.destructuringAssign = function (test) {
     "([ x ] = [ 1 ]);",
     // expressions
     "1, ({ x } = { x : 1 });",
-    "1, ([ x ] = [ 1 ]);"
+    "1, ([ x ] = [ 1 ]);",
+    "for (({ x } = { X: 1 }); ;) {}",
+    "for (; ;({ x } = { X: 1 })) {}"
   ];
 
   TestRun(test)
     .addError(2, 1, "Unnecessary grouping operator.")
     .addError(3, 4, "Unnecessary grouping operator.")
     .addError(4, 4, "Unnecessary grouping operator.")
+    .addError(5, 6, "Unnecessary grouping operator.")
+    .addError(6, 9, "Unnecessary grouping operator.")
     .test(code, { esversion: 6, singleGroups: true, expr: true });
 
   test.done();
diff --git a/tests/unit/parser.js b/tests/unit/parser.js
index 7680b477c3..15dfae989d 100644
--- a/tests/unit/parser.js
+++ b/tests/unit/parser.js
@@ -3148,7 +3148,8 @@ exports["let block and let expression"] = function (test) {
     "{",
     "  let(t=4) print(x, y, z, t);",
     "  print(let(u=4) u,x);",
-    "}"
+    "}",
+    "for (; ; let (x = 1) x) {}"
   ];
 
   TestRun(test)
@@ -3163,7 +3164,8 @@ exports["let block and let expression as esnext"] = function (test) {
     "{",
     "  let(t=4) print(x, y, z, t);",
     "  print(let(u=4) u,x);",
-    "}"
+    "}",
+    "for (; ; let (x = 1) x) {}"
   ];
 
   TestRun(test)
@@ -3171,6 +3173,8 @@ exports["let block and let expression as esnext"] = function (test) {
     .addError(3, 6, "'let block' is only available in Mozilla JavaScript extensions (use moz option).")
     .addError(4, 9, "'let expressions' is only available in Mozilla JavaScript extensions " +
       "(use moz option).")
+    .addError(6, 10, "'let expressions' is only available in Mozilla JavaScript extensions " +
+      "(use moz option).")
     .test(code, {esnext: true, unused: true, undef: true, predef: ["print"]});
   test.done();
 };