Changeset 186379 in webkit for trunk/Source/JavaScriptCore/parser/Parser.cpp

Timestamp:

Jul 6, 2015, 3:18:58 PM (10 years ago)

Author:

[email protected]

Message:

JSC's parser should follow the ES6 spec with respect to parsing Declarations
​https://bugs.webkit.org/show_bug.cgi?id=146621

Reviewed by Mark Lam.

Source/JavaScriptCore:

There were a few locations where JSC would allow declaration statements
in incorrect ways. JSC didn't distinguish between 'Statement' and
'StatementListItem' grammar productions. The relevant grammar is here:
​http://www.ecma-international.org/ecma-262/6.0/index.html#sec-statements

From the ECMA Script 6.0 spec:

1. Section 13.6 The if Statement (​http://www.ecma-international.org/ecma-262/6.0/index.html#sec-if-statement) says that IfStatements only takes Statements for the "then-else" clauses, not StatementListItems. (Same with 'while/for/do-while' loop bodies).
2. Section 13 ECMAScript Language: Statements and Declarations (​http://www.ecma-international.org/ecma-262/6.0/index.html#sec-ecmascript-language-statements-and-declarations) defines the syntax of Statements, and they do not include ClassDeclarations and LexicalDeclarations (const, let, see 13.3.1 Let and Const Declarations). Declarations can only be in the “then-else” clauses when embedded in a StatementListItem in a BlockStatement (see 13.2).

Hence, the following style of declarations are no longer allowed:

'if/for/while (condition) const x = 40;'
'if/for/while (condition) class C { }'

Instead, we mandate such declaration constructs are within a StatementList

(which is the production that JSC's Parser::parseSourceElements function parses):

'if/for/while (condition) { const x = 40; }'
'if/for/while (condition) { class C { } }'

• parser/Parser.cpp:

(JSC::Parser<LexerType>::parseSourceElements):
(JSC::Parser<LexerType>::parseStatementListItem):
(JSC::Parser<LexerType>::parseVarDeclaration):
(JSC::Parser<LexerType>::parseStatement):
(JSC::Parser<LexerType>::parseExpressionStatement):

• parser/Parser.h:

(JSC::Parser::getLabel):

LayoutTests:

• js/parser-syntax-check-expected.txt:
• js/script-tests/const.js:

(with1):
(with2):

• js/script-tests/parser-syntax-check.js:
• js/script-tests/statement-list-item-syntax-errors.js: Added.

(testSyntax):
(runTests):

• js/statement-list-item-syntax-errors-expected.txt: Added.
• js/statement-list-item-syntax-errors.html: Added.
• sputnik/Conformance/07_Lexical_Conventions/7.5_Tokens/7.5.3_Future_Reserved_Words/S7.5.3_A1.5-expected.txt:

File:

• trunk/Source/JavaScriptCore/parser/Parser.cpp (modified) (4 diffs)

trunk/Source/JavaScriptCore/parser/Parser.cpp

@@ -370 +370 @@
 #endif
     
-    while (TreeStatement statement = parseStatement(context, directive, &directiveLiteralLength)) {
+    while (TreeStatement statement = parseStatementListItem(context, directive, &directiveLiteralLength)) {
         if (mode == CheckForStrictMode && !seenNonDirective) {
             if (directive) {
@@ -402 +402 @@
     propagateError();
     return sourceElements;
+}
+template <typename LexerType>
+template <class TreeBuilder> TreeStatement Parser<LexerType>::parseStatementListItem(TreeBuilder& context, const Identifier*& directive, unsigned* directiveLiteralLength)
+{
+    // The grammar is documented here:
+    // http://www.ecma-international.org/ecma-262/6.0/index.html#sec-statements
+    TreeStatement result = 0;
+    switch (m_token.m_type) {
+    case CONSTTOKEN:
+        result = parseConstDeclaration(context);
+        break;
+#if ENABLE(ES6_CLASS_SYNTAX)
+    case CLASSTOKEN:
+        result = parseClassDeclaration(context);
+        break;
+#endif
+    default:
+        // FIXME: This needs to consider 'let' in bug:
+        // https://bugs.webkit.org/show_bug.cgi?id=142944
+        result = parseStatement(context, directive, directiveLiteralLength);
+        break;
+    }
+
+    return result;
 }
 
@@ -1264 +1288 @@
         result = parseVarDeclaration(context);
         break;
-    case CONSTTOKEN:
-        result = parseConstDeclaration(context);
-        break;
-#if ENABLE(ES6_CLASS_SYNTAX)
-    case CLASSTOKEN:
-        failIfFalse(m_statementDepth == 1, "Class declaration is not allowed in a lexically nested statement");
-        result = parseClassDeclaration(context);
-        break;
-#endif
     case FUNCTION:
         failIfFalseIfStrict(m_statementDepth == 1, "Strict mode does not allow function declarations in a lexically nested statement");
@@ -1939 +1954 @@
 template <class TreeBuilder> TreeStatement Parser<LexerType>::parseExpressionStatement(TreeBuilder& context)
 {
+    switch (m_token.m_type) {
+    // Consult: http://www.ecma-international.org/ecma-262/6.0/index.html#sec-expression-statement
+    // The ES6 spec mandates that we should fail from FUNCTION token here. We handle this case 
+    // in parseStatement() which is the only caller of parseExpressionStatement().
+    // We actually allow FUNCTION in situations where it should not be allowed unless we're in strict mode.
+    case CLASSTOKEN:
+        failWithMessage("'class' declaration is not directly within a block statement");
+        break;
+    default:
+        // FIXME: when implementing 'let' we should fail when we see the token sequence "let [".
+        // https://bugs.webkit.org/show_bug.cgi?id=142944
+        break;
+    }
     JSTextPosition start = tokenStartPosition();
     JSTokenLocation location(tokenLocation());