private Expr Assignment()
{
Expr expr = Or();
if (Match(TokenType.Equal))
{
Token equals = Previous();
Expr value = Assignment();
if (expr is Expr.Variable)
{
Token name = ((Expr.Variable)expr).name;
expr = new Expr.Assign(name, value);
}
else if (expr is Expr.Get)
{
Expr.Get get = (Expr.Get)expr;
expr = new Expr.Set(get.obj, get.name, value);
}
else
{
Error(equals, "Invalid assignment target.");
}
}
return(expr);
}
public object Visit(Expr.Set expr)
{
Resolve(expr.value);
Resolve(expr.obj);
return(null);
}
public object Visit(Expr.Set expr)
{
object obj = Evaluate(expr.obj);
if (!(obj is LoxInstance))
{
throw new RuntimeError(expr.name, "Only instances have fields.");
}
object value = Evaluate(expr.value);
((LoxInstance)obj).Set(expr.name, value);
return(value);
}