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Added an explanation for the lookahead.

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This commit is contained in:
Daniel Rosenwasser 2015-06-03 13:46:13 -07:00
parent 3cd480ddb6
commit 3fe308d2a6
1 changed files with 28 additions and 14 deletions
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42
src/compiler/parser.ts
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@ -3973,7 +3973,7 @@ module ts {
case SyntaxKind.ThrowKeyword:
return parseThrowStatement();
case SyntaxKind.TryKeyword:
// Include the next two for error recovery.
// Include 'catch' and 'finally' for error recovery.
case SyntaxKind.CatchKeyword:
case SyntaxKind.FinallyKeyword:
return parseTryStatement();
@ -3981,6 +3981,33 @@ module ts {
return parseDebuggerStatement();
case SyntaxKind.AtToken:
return parseDeclaration();
case SyntaxKind.ConstKeyword:
case SyntaxKind.EnumKeyword:
case SyntaxKind.ExportKeyword:
case SyntaxKind.ImportKeyword:
case SyntaxKind.InterfaceKeyword:
case SyntaxKind.PrivateKeyword:
case SyntaxKind.ProtectedKeyword:
case SyntaxKind.PublicKeyword:
case SyntaxKind.StaticKeyword:
if (getDeclarationFlags() & flags) {
return parseDeclaration();
}
break;
// 'declare', 'module', 'namespace', and 'type' are all legal JavaScript identifiers when ASI
// takes effect. In such cases, we cannot parse out the "expected" declarations. For instance, while
//
// namespace n
//
// can be none other than the beginning of a namespace declaration, JavaScript sees
//
// namespace
// n
//
// as the identifier 'namespace' on one line followed by the identifier 'n' on another.
// We need to look one token ahead to see if it permissible to try parsing a declaration.
case SyntaxKind.DeclareKeyword:
if (lookAhead(isFollowedByIdentifierOrKeywordOnSameLine) && getDeclarationFlags() & flags) {
return parseDeclaration();
@ -3997,19 +4024,6 @@ module ts {
return parseDeclaration();
}
break;
case SyntaxKind.ConstKeyword:
case SyntaxKind.EnumKeyword:
case SyntaxKind.ExportKeyword:
case SyntaxKind.ImportKeyword:
case SyntaxKind.InterfaceKeyword:
case SyntaxKind.PrivateKeyword:
case SyntaxKind.ProtectedKeyword:
case SyntaxKind.PublicKeyword:
case SyntaxKind.StaticKeyword:
if (getDeclarationFlags() & flags) {
return parseDeclaration();
}
break;
}
return parseExpressionOrLabeledStatement();
}