[Issue 13372] traits parent does not work on eponymous templates

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

Iain Buclaw  changed:

   What|Removed |Added

   Priority|P1  |P2

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[Issue 13372] traits parent does not work on eponymous templates

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

Adam D. Ruppe  changed:

   What|Removed |Added

 CC||destructiona...@gmail.com

--- Comment #5 from Adam D. Ruppe  ---
Here's something related I just came upon:

template wrap(string foo) {
enum wrap = foo;
}
pragma(msg, __traits(parent, wrap!"lol")); // says lol
pragma(msg, __traits(parent, __traits(parent, wrap!"lol"))); // says argument
"lol" has no parent


So in the first one, it appears it evaluates to the outer template which is
then instantly evaluated back to the enum literal. Then the second one sees the
literal and says literals have no parents.

Quite bizarre indeed.

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[Issue 13372] traits parent does not work on eponymous templates

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

Basile-z  changed:

   What|Removed |Added

 CC|b2.t...@gmx.com |

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[Issue 13372] traits parent does not work on eponymous templates

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

--- Comment #4 from Mike Franklin  ---
(In reply to Basile B. from comment #2)
> =
> import std.meta;
> 
> template Parent(T)
> {
> alias Parent = AliasSeq!(__traits(parent, T))[0];
> }
> 
> unittest
> {
> class A(T){}
> static assert(A!int.stringof != Parent!(A!int).stringof);
> }
> =
> 
> yields: Error: static assert  ("A!int" != "A!int") is false
> 
> 
> the longer form
> 
> =
> import std.meta;
> 
> template Parent(T)
> {
> alias Parent = AliasSeq!(__traits(parent, T))[0];
> }
> 
> unittest
> {
> template B(T){class B{}}
> alias T = B!int;
> static assert(is(T));
> static assert(T.stringof != Parent!T.stringof);
> }
> =
> 
> yields: Error: static assert  ("B!int" != "B!int") is false

These two tests now pass in v2.078.1

--

[Issue 13372] traits parent does not work on eponymous templates

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

Mike  changed:

   What|Removed |Added

   See Also||https://issues.dlang.org/sh
   ||ow_bug.cgi?id=12496

--

[Issue 13372] traits parent does not work on eponymous templates

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

--- Comment #3 from b2.t...@gmx.com ---
Strangely enough this bug can lead to think that we can detect an eponymous
template:

==
template isTemplateInstance(alias T : Base!Args, alias Base, Args...)
{
enum isTemplateInstance = is(typeof(T));
}

template isTemplateInstance(T : Base!Args, alias Base, Args...)
{
enum isTemplateInstance = is(T);
}

template isTemplateInstance(T)
{
enum isTemplateInstance = false;
}

template isTemplateInstance(alias T)
{
enum isTemplateInstance = isTemplateInstance!(typeof(T));
}

template isEponymousTemplate(T)
{
static if (is(T == class) || is(T == interface) || is(T == struct) || is(T
== union))
{
enum p = __traits(parent, T).stringof == T.stringof;
enum isEponymousTemplate = p && isTemplateInstance!T;
}
else
enum isEponymousTemplate = false;
}

unittest
{
class A(T){}
struct B(T){}
static assert(isEponymousTemplate!(A!int));
static assert(isEponymousTemplate!(B!int));
static assert(!isEponymousTemplate!int);
template C(T)
{
class C{}
}
static assert(isEponymousTemplate!(C!int));
}

unittest
{
template A(T)
{
class A{}
}
static assert(isEponymousTemplate!(A!int));

template B(T)
{
class A{}
}
static assert(!isEponymousTemplate!(B!int.A));

class C(T){}
static assert(!isEponymousTemplate!int);

A!int a;
static assert(isEponymousTemplate!a);
}
==

Indeed we can detect it but we can't get the parent !
What's happen is that "isEponymousTemplate" yield true for an eponymous
template because the template itself points to its argument !

--

[Issue 13372] traits parent does not work on eponymous templates

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

b2.t...@gmx.com changed:

   What|Removed |Added

   Hardware|x86_64  |All
 OS|Linux   |All

--

[Issue 13372] traits parent does not work on eponymous templates

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13372

b2.t...@gmx.com changed:

   What|Removed |Added

 CC||b2.t...@gmx.com
Summary|traits parent shows |traits parent does not work
   |template function as its|on eponymous templates
   |own parent  |
   Severity|normal  |major

--- Comment #2 from b2.t...@gmx.com ---
=
import std.meta;

template Parent(T)
{
alias Parent = AliasSeq!(__traits(parent, T))[0];
}

unittest
{
class A(T){}
static assert(A!int.stringof != Parent!(A!int).stringof);
=

yields: Error: static assert  ("A!int" != "A!int") is false


the longer form

=
import std.meta;

template Parent(T)
{
alias Parent = AliasSeq!(__traits(parent, T))[0];
}

unittest
{
template B(T){class B{}}
alias T = B!int;
static assert(is(T));
static assert(T.stringof != Parent!T.stringof);
}
=

yields: Error: static assert  ("B!int" != "B!int") is false


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