Simplify & fix rest argument validity checks.

acorn.js

@@ -315,7 +315,7 @@
   function initParserState() {
     lastStart = lastEnd = tokPos;
     if (options.locations) lastEndLoc = curPosition();
-    inFunction = inGenerator = strict = false;
+    inFunction = inGenerator = false;
     labels = [];
     skipSpace();
     readToken();
@@ -616,6 +616,7 @@
     tokType = _eof;
     tokContext = [b_stat];
     tokExprAllowed = true;
+    strict = false;
     if (tokPos === 0 && options.allowHashBang && input.slice(0, 2) === '#!') {
       skipLineComment(2);
     }
@@ -1523,8 +1524,10 @@
           break;
         case "SpreadElement":
           last.type = "RestElement";
-          toAssignable(last.argument);
-          checkSpreadAssign(last.argument);
+          var arg = last.argument;
+          toAssignable(arg);
+          if (arg.type !== "Identifier" && arg.type !== "ArrayPattern")
+            unexpected(arg.start);
           break;
         default:
           toAssignable(last);
@@ -1545,8 +1548,7 @@
   function parseRest() {
     var node = startNode();
     next();
-    node.argument = parseAssignableAtom();
-    checkSpreadAssign(node.argument);
+    node.argument = tokType === _name || tokType === _bracketL ? parseAssignableAtom() : unexpected();
     return finishNode(node, "RestElement");
   }
 
@@ -1598,13 +1600,6 @@
     return finishNode(node, "AssignmentPattern");
   }
 
-  // Checks if node can be assignable spread argument.
-
-  function checkSpreadAssign(node) {
-    if (node.type !== "Identifier" && node.type !== "ArrayPattern")
-      unexpected(node.start);
-  }
-
   // Verify that argument names are not repeated, and it does not
   // try to bind the words `eval` or `arguments`.
 
@@ -1691,7 +1686,11 @@
         break;
 
       case "AssignmentPattern":
+        checkLVal(expr.left);
+        break;
+
       case "RestElement":
+        checkLVal(expr.argument);
         break;
 
       default:

acorn_loose.js

@@ -325,9 +325,6 @@
   }
 
   function parseStatement() {
-    if (token.type === tt.slash || token.type === tt.assign && token.value === "/=")
-      next(true);
-
     var starttype = token.type, node = startNode();
 
     switch (starttype) {

test/tests-harmony.js

@@ -15013,3 +15013,6 @@ testFail("if (1) let x = 10;", "Unexpected token (1:7)", {ecmaVersion: 6});
 testFail("for (;;) const x = 10;", "Unexpected token (1:9)", {ecmaVersion: 6});
 testFail("while (1) function foo(){}", "Unexpected token (1:10)", {ecmaVersion: 6});
 testFail("if (1) ; else class Cls {}", "Unexpected token (1:14)", {ecmaVersion: 6});
+
+testFail("'use strict'; [...eval] = arr", "Assigning to eval in strict mode (1:18)", {ecmaVersion: 6});
+testFail("'use strict'; ({eval = defValue} = obj)", "Assigning to eval in strict mode (1:16)", {ecmaVersion: 6});