Making uniform function call syntax more complete a feature

[Thiez]

On Thursday, 12 July 2012 at 12:43:24 UTC, Tommi wrote:
> On Thursday, 12 July 2012 at 10:05:16 UTC, Thiez wrote:
>> Have you considered adding operator overloading using UFCS 
>> while you're at it?
>
> I assumed it's already possible to add operators 
> non-intrusively, because operators are just syntactic sugar for 
> method calls:
>
> ++var;              // actual code
> var.opUnary!"++"(); // lowered once
> opUnary!"++"(var);  // lowered twice (if necessary)
>
> If you're talking about overloading existing operators (which 
> have been implemented as member functions) non-intrusively for 
> other types, then I don't know, doesn't it work?

I actually tried those yesterday (with opEquals and opCmp on 
structs) and couldn't get it to work. Code still used what 
appeared to be an automatically generated opEquals (that appears 
to perform a bitwise comparison) instead of my UFCS opEquals.

It's already quite obvious that the compiler does not obey its 
own rewrite rules (see 
http://dlang.org/operatoroverloading.html#compare) Consider opCmp:
  a < b
is rewritten to
  a.opCmp(b) < 0
or
  b.opCmp(a) > 0
Let's assume the first rule is always chosen. According to the 
very rewrite rule we just applied, this must be rewritten to
  a.opCmp(b).opCmp(0) < 0
which must be rewritten to
  a.opCmp(b).opCmp(0).opCmp(0) < 0
and then
  a.opCmp(b).opCmp(0).opCmp(0).opCmp(0) < 0
and so on, to infinity.

It seems quite obvious the compiler does not rewrite compares on 
integers or all hell would break loose... The language reference 
should be more specific about these things.