Bug 10488 – Allow template this parameter to work with static functions

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 !()()

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.

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.

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/[email protected] Therefore I'm reopening this issue as an enhancement request.

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

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.

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

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

@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

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

@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 <[email protected]> Co-authored-by: Dennis <[email protected]> https://github.com/dlang/dmd/pull/14482

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