__CLASS__ doesn't issue an experimental warning

[ikegami]

tags: 5.40.0 core class experimental warnings

__CLASS__ doesn't issue an warning identifying it as experimental like class, field, ADJUST, etc do.

$ perl -v | grep 'This is'
This is perl 5, version 40, subversion 0 (v5.40.0) built for x86_64-linux-thread-multi

$ perl -e'use feature qw( class ); class Foo { }'
class is experimental at -e line 1.

$ perl -e'use feature qw( class ); field'
field is experimental at -e line 1.
Cannot 'field' outside of a 'class' at -e line 1.

$ perl -e'use feature qw( class ); ADJUST { }'
ADJUST is experimental at -e line 1.
Cannot 'ADJUST' outside of a 'class' at -e line 1.

$ perl -e'use feature qw( class ); __CLASS__'
Cannot use __CLASS__ outside of a method or field initializer expression at -e line 1.

It's moot since it can't be used outside of class and using class does warn, but it's inconsistent with other such keywords, and it could become important if class stops being experimental before __CLASS__.

[rwp0]

I believe that's reasonable since method keyword also warns:

> perl -Mfeature=class -E "method {}"

method is experimental at -e line 1.

Cannot 'method' outside of a 'class' at -e line 1.

Searching I couldn't locate where to mark that as experimental, and that's not documented in:

https://github.com/Perl/perl5/blob/blead/pod/perldiag.pod

[jkeenan]

@leonerd, can you take a look at this ticket? Thanks.