http://d.puremagic.com/issues/show_bug.cgi?id=5988

           Summary: Error when template is instantiated in a class
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Mac OS X
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: robert@octarineparrot.com


--- Comment #0 from Robert Clipsham <robert@octarineparrot.com> 2011-05-12 18:43:25 BST ---
The following code:
----
template Templ(alias T)
{
    alias T!int Templ;
}

class C(T)
{
    Templ!C foo;
}

// Uncomment this to make the error go away
//Templ!C foo;

void main()
{
    C!int a;
}
----
Gives the error:
----
test.d(3): Error: template instance T is not a template declaration, it is a
class
----
When uncommenting the line mentioned in the code the error goes away, presumably because the forward reference goes away.

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--- Comment #1 from Robert Clipsham <robert@octarineparrot.com> 2011-05-12 20:19:19 BST ---
This issue can be worked around using:
----
alias C Workaround;
class C(T)
{
    Templ!Workaround foo;
}
----
This shouldn't be needed though.

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kennytm@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kennytm@gmail.com


--- Comment #2 from kennytm@gmail.com 2011-05-12 19:35:48 PDT ---
This is because that class template is actually

    template C(T) {
      class C {
        <declarations>
      }
    }

so the C inside is referring to the class C, not the template C. This code works:

    class C(T) {
      Templ!(.C) foo;
    }

I don't know why uncomment the global instantiation makes the problem goes away.

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|rejects-valid               |accepts-invalid
                 CC|                            |andrej.mitrovich@gmail.com
         OS/Version|Mac OS X                    |All


--- Comment #3 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-02-09 06:06:21 PST ---
(In reply to comment #2)
> This is because that class template is actually
> 
>     template C(T) {
>       class C {
>         <declarations>
>       }
>     }
> 
> so the C inside is referring to the class C, not the template C. This code works:
> 
>     class C(T) {
>       Templ!(.C) foo;
>     }
> 
> I don't know why uncomment the global instantiation makes the problem goes away.

Yeah, this is an accepts-invalid for this test-case:

template Templ(alias T)
{
    alias T!int Templ;
}

class C(T)
{
    Templ!(C) foo;  // should be NG, must use Templ!(.C)
}

Templ!C foo;

void main()
{
    C!int a;
}

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--- Comment #4 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-02-09 06:08:43 PST ---
(In reply to comment #3)
> Yeah, this is an accepts-invalid for this test-case:
> 
> template Templ(alias T)
> {
>     alias T!int Templ;
> }
> 
> class C(T)
> {
>     Templ!(C) foo;  // should be NG, must use Templ!(.C)
> }
> 
> Templ!C foo;
> 
> void main()
> {
>     C!int a;
> }

I think the cause could perhaps be a mangling issue or the way the compiler searches for template instances. It finds a 'Templ!C' and decides to use that instead of instantiating a new 'Templ!C', where 'C' is something completely different.

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--- Comment #5 from Kenji Hara <k.hara.pg@gmail.com> 2013-05-18 03:11:11 PDT ---
(In reply to comment #3)
> Yeah, this is an accepts-invalid for this test-case:
> 
> template Templ(alias T)
> {
>     alias T!int Templ;
> }
> 
> class C(T)
> {
>     Templ!(C) foo;  // should be NG, must use Templ!(.C)
> }
> 
> Templ!C foo;
> 
> void main()
> {
>     C!int a;
> }

No. This is rejects-valid issue. Templ!(C) would capture class C (not template
C), BUT, inside Templ, T!int should be translated to the instantiation of
template C.

The behavior is consistent with the following:

class C(T) {
    void foo() {
        C!long c;
        // here 'C' points class (not template), but C!long will
        // automatically translated to the template C instantiation.
    }
}
C!int c;

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|accepts-invalid             |pull, rejects-valid
           Platform|Other                       |All


--- Comment #6 from Kenji Hara <k.hara.pg@gmail.com> 2013-05-18 03:11:54 PDT ---
https://github.com/D-Programming-Language/dmd/pull/2051

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--- Comment #7 from github-bugzilla@puremagic.com 2013-06-25 00:32:39 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/d683a052674722d5320a6de44cf2f7456e80b8f7
fix Issue 5988 - Template accepts instantiating an already-instantiated
template type

https://github.com/D-Programming-Language/dmd/commit/771c99c6ccf34032a8cc43f5462caa9e3457630e Merge pull request #2051 from 9rnsr/fix5988

Issue 5988 - Template accepts instantiating an already-instantiated template type

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


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