Function prototype overloading does not work ?

[Steven Schveighoffer]

On 1/19/22 3:47 AM, Enjoys Math wrote:
> ```
> module expr;
> 
> import dots;
> import operator;
> import equation;
> import var;
> import var_expr;
> import zz_const;
> 
> class Expr
> {
> public:
>     void opBinary(string op)(string s) const
>     {
>        static if (op == "+")
>        {
>           Expr right = null;
> 
>           if (s == ".." || s == "..." || s == "....")
>           {
>              right = new Dots();
>           }
> 
>           if (right !is null)
>              return new Op("+", [this, right]);
>        }
>     }
> 
>     override string toString() const
>     {
>        assert(0);
>     }
> 
>     Expr sub(Expr x, Expr y)
>     {
>        if (this == x)
>           return y;
>        return this;
>     }
> 
>     Expr sub(Expr x, ref Var y)
>     {
>        return sub(x, new VarExpr(y));
>     }
> 
>     Expr sub(ref Var x, Expr y)
>     {
>        return sub(new VarExpr(x), y);
>     }
> 
>     Expr sub(int x, Expr y)
>     {
>        return sub(ZZ(x), y);
>     }
> 
>     Expr sub(Expr x, int y)
>     {
>        return sub(x, ZZ(y));
>     }
> 
>     Expr sub(ref Var x, ref Var y)
>     {
>        return sub(new VarExpr(x), new VarExpr(y));
>     }
> 
>     Expr sub(ref Var x, int y)
>     {
>        return sub(new VarExpr(x), ZZ(y));
>     }
> 
>     Expr sub(int x, ref Var y)
>     {
>        return sub(ZZ(x), new VarExpr(y));
>     }
> 
>     override bool opEquals(Object o) {
>        return this is o;
>     }
> }
> ```
> See all the overloads I had to make to sub in order to bypass identity 
> assignment for classes.  I.e. Var can't be of type Expr.  Anyway, this 
> approach is not working because code calling `Expr.sub(int, Var)` is not 
> seeing the definitions.  It says no function matching those args, but 
> clearly there are!
> 

sub(int, ref Var) exists, but not sub(int, Var). Is your Var an lvalue?

Without more code context, this is hard to diagnose. Can you post the 
offending call?

-Steve