private object EvaluateLiteralExpression(LiteralExpression expr)
{
return(expr.Value.Or(null));
}
private SyntaxNode ParseForStatement()
{
Consume(SyntaxKind.LeftParen, "expect'(' after 'for'.");
SyntaxNode initializer;
if (Match(SyntaxKind.Semicolon))
{
initializer = null;
}
else if (Match(SyntaxKind.Var))
{
initializer = ParseVariableDeclaration();
}
else
{
initializer = ParseExpressionStatement();
}
SyntaxNode condition = null;
if (!Check(SyntaxKind.Semicolon))
{
condition = ParseExpression();
}
Consume(SyntaxKind.Semicolon, "expect';' after loop condition.");
SyntaxNode increment = null;
if (!Check(SyntaxKind.RightParen))
{
increment = ParseExpression();
}
Consume(SyntaxKind.RightParen, "expect ')' after for clauses.");
SyntaxNode body = ParseStatement();
// desugar into a while loop
if (increment != null)
{
body = new BlockStatement(new List <SyntaxNode> {
body, new ExpressionStatement(increment)
});
}
if (condition == null)
{
condition = new LiteralExpression(true);
}
body = new WhileStatement(condition, body);
if (initializer != null)
{
body = new BlockStatement(new List <SyntaxNode> {
new ExpressionStatement(initializer), body
});
}
return(body);
}