Changeset 266327 in webkit for trunk/Source/JavaScriptCore

Timestamp:

Aug 29, 2020, 1:44:20 PM (5 years ago)

Author:

[email protected]

Message:

[JSC] let [ sequence cannot appear in ExpressionStatement context
​https://bugs.webkit.org/show_bug.cgi?id=215977

Reviewed by Ross Kirsling.

JSTests:

• stress/let-and-open-bracket.js: Added.

(testSyntax):
(testSyntaxError):

• test262/expectations.yaml:

Source/JavaScriptCore:

Because of ambiguity between destructuring assignment and member access (let IDENTIFIER), ECMA262 does not allow let [ sequence in ExpressionStatement context[1].
We should throw SyntaxError when we see something like this.

if (false)

let [ok] = [42];

[1]: ​https://tc39.es/ecma262/#sec-expression-statement

• parser/Parser.cpp:

(JSC::Parser<LexerType>::parseStatement):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• parser/Parser.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2020-08-29  Yusuke Suzuki  <[email protected]>
+
+        [JSC] `let [` sequence cannot appear in ExpressionStatement context
+        https://bugs.webkit.org/show_bug.cgi?id=215977
+
+        Reviewed by Ross Kirsling.
+
+        Because of ambiguity between destructuring assignment and member access (let IDENTIFIER), ECMA262 does not allow `let [` sequence in ExpressionStatement context[1].
+        We should throw SyntaxError when we see something like this.
+
+            if (false)
+                let [ok] = [42];
+
+        [1]: https://tc39.es/ecma262/#sec-expression-statement
+
+        * parser/Parser.cpp:
+        (JSC::Parser<LexerType>::parseStatement):
+
 2020-08-29  Yusuke Suzuki  <[email protected]>
 

trunk/Source/JavaScriptCore/parser/Parser.cpp

@@ -1971 +1971 @@
         return 0;
     case LET: {
+        // https://tc39.es/ecma262/#sec-expression-statement
+        // ExpressionStatement's lookahead includes `let [` sequence.
+        SavePoint savePoint = createSavePoint(context);
+        next();
+        failIfTrue(match(OPENBRACKET), "Cannot use lexical declaration in single-statement context");
+        restoreSavePoint(context, savePoint);
         if (!strictMode())
             goto identcase;