http://d.puremagic.com/issues/show_bug.cgi?id=9257

           Summary: [ER] New optional "operator" keyword to validate magic
                    functions
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: monarchdodra@gmail.com


--- Comment #0 from monarchdodra@gmail.com 2013-01-02 07:44:54 PST ---
Rationale:
When writing an operator, one might accidentally typo, use the wrong signature,
use the wrong name, use an un-existing name etc. Because the compiler relies on
only checking function names, the end user has no way to check if the code is
correct, appart from "noticing" that calling the operator doesn't work.

This can become quite clumsy once the more complicated things, like "opIndexOpAssign" (or was that "opOpIndexAssign" ?) get involved.

Description:
When writing a function with a "magic" name, one can prefix it with the keyword
operator. If that function name doesn't match any of the special functions,
with the correct amount of arguments, then a compile error is thrown:

//----
struct S
{
  operator opBinary(string op)(S rhs); //Fine
  operator opBinary(string op)(S rhs1, S rhs2); //Error, wrong number of
arguments
  operator opOpBinary(string op)(Type rhs); //Error, did you mean opOpAssign?
  operator opcmp(Type rhs); //Error, did you mean opCmp?
  static bool opEquals(S s1, S s2); //Error, opEquals cannot be declared as
static
}
//----

This would help with keeping in line with D's safety standard, in particular, the override keyword.

(from the discussion:
http://forum.dlang.org/thread/iubdngjksicwxugrqesc@forum.dlang.org)

Also want to point out: This bug has even made it into phobos.

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bearophile_hugs@eml.cc changed:

           What    |Removed                     |Added
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                 CC|                            |bearophile_hugs@eml.cc


--- Comment #1 from bearophile_hugs@eml.cc 2013-01-02 09:41:47 PST ---
(In reply to comment #0)

>   operator opBinary(string op)(S rhs); //Fine
>   operator opBinary(string op)(S rhs1, S rhs2); //Error, wrong number of
> arguments
>   operator opOpBinary(string op)(Type rhs); //Error, did you mean opOpAssign?
>   operator opcmp(Type rhs); //Error, did you mean opCmp?
>   static bool opEquals(S s1, S s2); //Error, opEquals cannot be declared as
> static
> }
> //----
> 
> This would help with keeping in line with D's safety standard, in particular, the override keyword.
> 
> (from the discussion:
> http://forum.dlang.org/thread/iubdngjksicwxugrqesc@forum.dlang.org)

Thank you for opening a ER. I was too much busy to do it.

I don't know if the solution proposed here is the right one, but being aware that a problem exists is the first step toward its solution.

Probably a pseudo-keyword like "@operator" is more reasonable than "operator".


> Also want to point out: This bug has even made it into phobos.

I suggest to show here some of the lines of code that contain that bug.

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--- Comment #2 from monarchdodra@gmail.com 2013-01-02 09:52:39 PST ---
(In reply to comment #1)
> > Also want to point out: This bug has even made it into phobos.
> 
> I suggest to show here some of the lines of code that contain that bug.

I've since fixed it: https://github.com/D-Programming-Language/phobos/commit/69d3a930b9d448d24b061ffc60d252ca056cb33e#L0R1805

It was really "just" a typo: "opOpassign" instead of "opOpAssign".

But still, the language shouldn't allow for "just a typo" kind of errors.

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