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digitalmars.D.bugs - [Issue 8261] New: std.traits.ParameterTypeTuple may break existing codes

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8261

           Summary: std.traits.ParameterTypeTuple may break existing codes
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: k.hara.pg gmail.com



In 2.060head, is(FuncType PT == function) -> PT contains parameter identifiers.
This change is introduced the commit:

https://github.com/D-Programming-Language/dmd/commit/65acb8ca382f3cd2abea058552d78c147163a8fa

It is useful for more metaprogramming, but this change may break existing codes
that using std.traits.ParameterTypeTuple. See below sample code:

void foo(int num, string name, int[int] map){}
pragma(msg, ParameterTypeTuple!foo);
  // In 2.059,     prints (int, string, int[int])
  // In 2.060head, prints (int num, string name, int[int] map)

void bar(ParameterTypeTuple!foo num) {}
// Error: function test.bar parameter bar.num is already defined

====

If we change the implementation of ParameterTypeTuple template like follows:

template ParameterTypeTuple(func...)
    if (func.length == 1 && isCallable!func)
{
    static if (is(FunctionTypeOf!(func) P == function))
    {
        //alias P ParameterTypeTuple;

        // Remove parameter names that original function has.
        template Id(T) { alias T Id; }
        alias staticMap!(Id, P) ParameterTypeTuple;
    }
    else
        static assert(0, "argument has no parameters");
}

We can get 'a tuple that contains only parameter types', but it also removes
parameter storage class... breaking existing codes REVISITED!

void foo(ref int x){}
pragma(msg, ParameterTypeTuple!foo); // will prints (int), not (ref int)


====

In current dmd, all of function parameters have names, written by user, or
named by compiler internally (e.g. _param_0). Then we never get a tuple of
'parameter type with storage class but unnamed'.
Then, if we want to parameter type tuple with storage classes, we cannot remove
parameter name informations from the tuple.
As far as I know, there is no workaround. So I think we should revert the
commit 65acb8ca.

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Jun 18 2012
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8261


Manu <turkeyman gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |turkeyman gmail.com





 In 2.060head, is(FuncType PT == function) -> PT contains parameter identifiers.
 This change is introduced the commit:
 
 https://github.com/D-Programming-Language/dmd/commit/65acb8ca382f3cd2abea058552d78c147163a8fa
 
 It is useful for more metaprogramming, but this change may break existing codes
 that using std.traits.ParameterTypeTuple. See below sample code:
 
 void foo(int num, string name, int[int] map){}
 pragma(msg, ParameterTypeTuple!foo);
   // In 2.059,     prints (int, string, int[int])
   // In 2.060head, prints (int num, string name, int[int] map)
 
 void bar(ParameterTypeTuple!foo num) {}
 // Error: function test.bar parameter bar.num is already defined
 
 ====
 
 If we change the implementation of ParameterTypeTuple template like follows:
 
 template ParameterTypeTuple(func...)
     if (func.length == 1 && isCallable!func)
 {
     static if (is(FunctionTypeOf!(func) P == function))
     {
         //alias P ParameterTypeTuple;
 
         // Remove parameter names that original function has.
         template Id(T) { alias T Id; }
         alias staticMap!(Id, P) ParameterTypeTuple;
     }
     else
         static assert(0, "argument has no parameters");
 }
 
 We can get 'a tuple that contains only parameter types', but it also removes
 parameter storage class... breaking existing codes REVISITED!
 
 void foo(ref int x){}
 pragma(msg, ParameterTypeTuple!foo); // will prints (int), not (ref int)
 
 
 ====
 
 In current dmd, all of function parameters have names, written by user, or
 named by compiler internally (e.g. _param_0). Then we never get a tuple of
 'parameter type with storage class but unnamed'.
 Then, if we want to parameter type tuple with storage classes, we cannot remove
 parameter name informations from the tuple.
 As far as I know, there is no workaround. So I think we should revert the
 commit 65acb8ca.


Can the new behaviour be expressed with a new ParameterTuple! trait or
something?
ParameterTypeTuple! makes sense as just types, but it would be nice to see a
suite: ParameterTyple! with all details, ParameterNameTuple! just names,
ParameterDefaultArgTuple!, you get the idea... ?

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Jun 18 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8261


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com



17:16:17 PDT ---
You're right, it does break existing code. I thought it was a worthwhile
tradeoff to get the functionality Manu needed.

But perhaps Manu's idea to do this tuple with a __traits is a better idea.

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Jun 18 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8261






 You're right, it does break existing code. I thought it was a worthwhile
 tradeoff to get the functionality Manu needed.
 
 But perhaps Manu's idea to do this tuple with a __traits is a better idea.


See also the notes in github.
https://github.com/D-Programming-Language/dmd/commit/65acb8ca382f3cd2abea058552d78c147163a8fa#commitcomment-1473583

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Jun 18 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8261


Kenji Hara <k.hara.pg gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull, rejects-valid
           Severity|normal                      |regression



I think this is a regression in 2.060head.
https://github.com/D-Programming-Language/dmd/pull/1018


To support getting parameter names, there are two pulls.

1. Add new trait: __traits(parameterNames, func)
https://github.com/D-Programming-Language/dmd/pull/951

2. An implementation of my idea: __traits(identifier, typeof(func))
https://github.com/D-Programming-Language/dmd/pull/1017

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Jun 19 2012
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8261


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED



00:44:00 PDT ---
Done in an alternate way:

https://github.com/D-Programming-Language/dmd/commit/08811d7abbb6cd6eeabef041122e1673b2044251

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