http://d.puremagic.com/issues/show_bug.cgi?id=4639

           Summary: Built-in primitive types cannot be used as template
                    alias parameters
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: asitdepends@gmail.com


--- Comment #0 from Deokjae Lee <asitdepends@gmail.com> 2010-08-13 00:45:55 PDT ---
import std.stdio;

template T(alias X) {
}

void main() {
    writeln(typeid(typeof(T!int)));
}

dmd 2.048 on linux produces an error for the above code.

Error: template instance T!(int) does not match template declaration T(alias X)

Built-in primitive types cannot be used as template alias parameters. Structs and classes work well.

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |clugdbug@yahoo.com.au
         Resolution|                            |INVALID


--- Comment #1 from Don <clugdbug@yahoo.com.au> 2010-08-13 04:10:04 PDT ---
This is not a bug. From the spec:
"Alias parameters enable templates to be parameterized with any type of D
symbol, including global names, local names, typedef names, module names,
template names, and template instance names. Literals can also be used as
arguments to alias parameters."

Built-in types are not on that list.

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--- Comment #2 from Deokjae Lee <asitdepends@gmail.com> 2010-08-13 08:47:32 PDT ---
(In reply to comment #1)
> This is not a bug. From the spec:
> "Alias parameters enable templates to be parameterized with any type of D
> symbol, including global names, local names, typedef names, module names,
> template names, and template instance names. Literals can also be used as
> arguments to alias parameters."
> 
> Built-in types are not on that list.


Hmm.. I don't think so.

"parameterized with any type of D symbol, including ..."

Why are not built-in primitive types included in "any type of D symbol"?
Is there any particular reason that user defined type names (like struct names)
are allowed but built-in type names are not allowed? I think such a limitation
is not natural.
IMHO, If there is any good reason for the limitation, the phrase "any type of D
symbol" should be removed from the spec. If there are no such reasons, then
this should be considered as a bug.

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--- Comment #3 from Don <clugdbug@yahoo.com.au> 2010-08-13 12:02:20 PDT ---
(In reply to comment #2)
> (In reply to comment #1)
> > This is not a bug. From the spec:
> > "Alias parameters enable templates to be parameterized with any type of D
> > symbol, including global names, local names, typedef names, module names,
> > template names, and template instance names. Literals can also be used as
> > arguments to alias parameters."
> > 
> > Built-in types are not on that list.
> 
> 
> Hmm.. I don't think so.
> 
> "parameterized with any type of D symbol, including ..."
> 
> Why are not built-in primitive types included in "any type of D symbol"?
> Is there any particular reason that user defined type names (like struct names)
> are allowed but built-in type names are not allowed? I think such a limitation
> is not natural.

I basically agree with you, but syntactically, they are quite different, and it's an intentional decision by Walter. See for example bug 1341.

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--- Comment #4 from Deokjae Lee <asitdepends@gmail.com> 2010-08-13 21:06:48 PDT ---
Still I could not get the reason.
So, I posted a message to the mailing list to discuss this.

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nfxjfg@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |nfxjfg@gmail.com
            Version|D2                          |D1 & D2
         Resolution|INVALID                     |


--- Comment #5 from nfxjfg@gmail.com 2010-08-13 21:20:46 PDT ---
This spec is way to sh... I mean incomplete to interpret it literally. Also it is known that the spec is downright incorrect in many cases. I don't know why you would close this bug as invalid just because of the spec text. Also it's very inconsistent to exclude built-in types. About it being intentional by Walter: he actually fixed the mentioned bug 1341 and didn't close it as invalid. Finally, it's a D1 problem too.

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |INVALID


--- Comment #6 from Don <clugdbug@yahoo.com.au> 2010-08-13 22:33:12 PDT ---
>It's exactly the same issue as: typeof(int) is not legal.(In reply to comment #5)
> This spec is way to sh... I mean incomplete to interpret it literally. Also it is known that the spec is downright incorrect in many cases. I don't know why you would close this bug as invalid just because of the spec text.

NO. I requested Walter to make this change, and he rejected this before. It is definitely NOT a bug. A built-in type is not a D symbol.

> Also it's
> very inconsistent to exclude built-in types. About it being intentional by
> Walter: he actually fixed the mentioned bug 1341 and didn't close it as
> invalid.

No, *I* changed the description of the bug after discussion with Walter. It was originally "typeof(int) should probably be legal".

> Finally, it's a D1 problem too.

No it isn't. It's an enhancement which would break existing code.

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--- Comment #7 from nfxjfg@gmail.com 2010-08-13 22:55:26 PDT ---
(In reply to comment #6)
> NO. I requested Walter to make this change, and he rejected this before. It is definitely NOT a bug. A built-in type is not a D symbol.

That's seriously stupid. Just another un-orthogonal feature that causes programmers headaches?

> No it isn't. It's an enhancement which would break existing code.

How?

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Max Samukha <samukha@voliacable.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |samukha@voliacable.com


--- Comment #8 from Max Samukha <samukha@voliacable.com> 2010-08-14 01:45:44 PDT ---
I can't believe the limitation is deliberate. Please remove it if technically possible. Now the poor coder is forced to practice nonsense like:

template Foo(A...) if (A.length == 1) {}

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