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digitalmars.D.bugs - [Issue 8062] New: UFCS and operator overloading

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8062

           Summary: UFCS and operator overloading
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: jens.k.mueller gmx.de



According to TDPL (p. 388, Table 12.1)
a + b
is rewritten to
a.opBinary!("+")(b) or b.opBinaryRight!("+")(a)

Considering operator overloading together with UFCS leads to the following
wrong behavior.

struct Foo {}

Foo opBinary(string op)(Foo lhs, Foo rhs) if (op == "+")
{   
    return Foo.init;
}

unittest
{   
    Foo a, b;
    a + b; // fails to compile even though it should
}

If a + b is rewritten to a.opBinary!("+")(b) first, then UFCS should rewrite it
further to opBinary!("+")(a,b). But it seems UFCS is not considered. UFCS
should be carried out when the operator is being rewritten.

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May 08 2012
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8062


Dmitry Olshansky <dmitry.olsh gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dmitry.olsh gmail.com



06:21:54 PDT ---
As defined t shouldn't:
UFCS presently only does go from fn(a,b, ...) -> a.fn(b, ...); way.

And arguably rightfully so, as it already may introduce some hijacking.

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May 31 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8062


timon.gehr gmx.ch changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |timon.gehr gmx.ch





 As defined t shouldn't:
 UFCS presently only does go from fn(a,b, ...) -> a.fn(b, ...); way.
 


Well, no. UFCS transforms a.fn(b, ...) to fn(a,b, ...).


 And arguably rightfully so, as it already may introduce some hijacking.


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Jun 13 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8062




12:22:05 PDT ---




 As defined t shouldn't:
 UFCS presently only does go from fn(a,b, ...) -> a.fn(b, ...); way.
 


 
 Well, no. UFCS transforms a.fn(b, ...) to fn(a,b, ...).


My bad, I actually meant it a.fn ---> fn(a,...) way. Which brings us to the
point  - request is Invalid then?

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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 My bad, I actually meant it a.fn ---> fn(a,...) way. Which brings us to the
 point  - request is Invalid then?


I don't think it is invalid.

a + b -> a.opBinary!"+"(b) -> opBinary!"+"(a, b);

Probably this is on the borderline between bug and enhancement request -- I
think the documentation can be interpreted either way.

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prev sibling parent d-bugmail puremagic.com writes:
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 My bad, I actually meant it a.fn ---> fn(a,...) way. Which brings us to the
 point  - request is Invalid then?


 
 I don't think it is invalid.
 
 a + b -> a.opBinary!"+"(b) -> opBinary!"+"(a, b);
 
 Probably this is on the borderline between bug and enhancement request -- I
 think the documentation can be interpreted either way.


Which documentation are you referring to? I don't think this is an enhancement.
How can it be an enhancement? Are there exceptions when UFCS has to be applied?

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