public object Visit(Expr.This expr)
{
if (currentClass == ClassType.None)
{
Lox.Error(expr.keyword, "Cannot use 'this' outside of a class.");
}
else
{
ResolveLocal(expr, expr.keyword);
}
return(null);
}
private Expr Primary()
{
Expr expr = null;
if (Match(TokenType.False))
{
expr = new Expr.Literal(false);
}
else if (Match(TokenType.True))
{
expr = new Expr.Literal(true);
}
else if (Match(TokenType.Nil))
{
expr = new Expr.Literal(null);
}
else if (Match(TokenType.Number, TokenType.String))
{
expr = new Expr.Literal(Previous().literal);
}
else if (Match(TokenType.Super))
{
Token keyword = Previous();
Consume(TokenType.Dot, "Expect '.' after 'super'.");
Token method = Consume(TokenType.Identifier, "Expect superclass method name.");
expr = new Expr.Super(keyword, method);
}
else if (Match(TokenType.This))
{
expr = new Expr.This(Previous());
}
else if (Match(TokenType.Identifier))
{
expr = new Expr.Variable(Previous());
}
else if (Match(TokenType.LeftParen))
{
expr = Expression();
Consume(TokenType.RightParen, "Expect ')' after expression.");
expr = new Expr.Grouping(expr);
}
else
{
throw Error(Peek(), "Expect expression.");
}
return(expr);
}
public object Visit(Expr.This expr)
{
return(LookUpVariable(expr.keyword, expr));
}