Allow template this parameter to work with static functions

[dlangBugzillaToGithub]

Jacob Carlborg (@jacob-carlborg) reported this on 2013-06-27T08:54:06Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=10488

CC List

• Orvid King
• Adam D. Ruppe
• Max Samukha
• Nick Treleaven (@ntrel)
• Marc Schütz

Description

This code compiled with 2.062:

class Foo
{
	static void instance (this T) ()
	{
	}
}

void main ()
{
	Foo.instance();
}

With 2.063 I get this error:

main.d(10): Error: template main.Foo.instance does not match any function template declaration. Candidates are:
main.d(3):        main.Foo.instance(this T)()
main.d(10): Error: template main.Foo.instance(this T)() cannot deduce template function from argument types !()()

[dlangBugzillaToGithub]

k.hara.pg commented on 2013-06-27T20:50:38Z

That was "accepts-invalid" bug.
Even with 2.062, it didn't work properly.

class Foo
{
    static void instance (this T) () {}
}
void main ()
{
    import std.typetuple;
    foreach (T; TypeTuple!(Foo, const Foo, immutable Foo))
    {
        pragma(msg, T);
        T.instance();  // fail to compile with const and immutable
    }
}

static member function does not have valid 'this' expression, so compiler cannot deduce TemplateThisParameter with IFTI.

[dlangBugzillaToGithub]

doob (@jacob-carlborg) commented on 2013-06-28T01:29:36Z

I thought that the whole point was to use it when "this" wasn't normally allowed. Just like typeof(this) can be used outside instance methods.

[dlangBugzillaToGithub]

schuetzm commented on 2015-10-25T12:02:53Z

IMO the fact that `typeof(this)` is allowed in static methods is a compelling argument to allow this. It has interesting applications when combined with inheritance, see this forum post:

http://forum.dlang.org/post/n0gl6m$1oms$1@digitalmars.com

Therefore I'm reopening this issue as an enhancement request.

[dlangBugzillaToGithub]

nick (@ntrel) commented on 2018-02-01T13:41:05Z

*** Issue 17713 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

nick (@ntrel) commented on 2018-02-01T13:42:25Z

The above duplicate has a nice test case and also a comment that template this should be allowed anywhere inside a class, not just static function templates.

[dlangBugzillaToGithub]

nick (@ntrel) commented on 2018-03-09T19:06:07Z

*** Issue 14191 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

nick (@ntrel) commented on 2022-09-14T13:26:32Z

*** Issue 20277 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

dlang-bot commented on 2022-09-16T13:24:34Z

@ntrel created dlang/dmd pull request #14446 "Infer template this parameter when calling static method on instance" mentioning this issue:

- Infer template this parameter when calling static method on instance
  
  Part of Issue 10488 - Allow template this parameter with static functions.
  
  Note: `tthis` is only used in `doHeaderInstantiation` for template this
  so assigning null when there's a static storage class is not needed for
  anything else.

https://github.com/dlang/dmd/pull/14446

[dlangBugzillaToGithub]

dlang-bot commented on 2022-09-26T02:35:02Z

dlang/dmd pull request #14446 "Infer template this parameter when calling static method on instance" was merged into master:

- 0121a59283ab9eb20b8fff646f90df7bd3fbfe13 by Nick Treleaven:
  Infer template this parameter when calling static method on instance
  
  Part of Issue 10488 - Allow template this parameter with static functions.

https://github.com/dlang/dmd/pull/14446

[dlangBugzillaToGithub]

dlang-bot commented on 2022-09-27T14:46:41Z

@maxhaton updated dlang/dmd pull request #14482 "Fix Issue 23368 - Don't segfault on throwing null exception" mentioning this issue:

- Infer template this parameter when calling static method on instance (#14446)
  
  * Infer template this parameter when calling static method on instance
  
  Part of Issue 10488 - Allow template this parameter with static functions.
  
  * Apply suggestions from code review
  
  Co-authored-by: Dennis <dkorpel@users.noreply.github.com>
  
  Co-authored-by: Dennis <dkorpel@users.noreply.github.com>

https://github.com/dlang/dmd/pull/14482