please 'use experimental :pack' even if code does exactly that

[AlexDaniel]

Originally reported by @thundergnat++, confirmed by @dogbert17++, golfed by @ugexe++:

$ perl6 -e 'package Foo { use experimental :pack; sub go() is export { "".encode.unpack("*") }; }; import Foo; go()'
Use of the 'unpack' method is experimental; please 'use experimental :pack'
  in sub go at -e line 1
  in block <unit> at -e line 1

Original report in a gist: https://gist.github.com/thundergnat/057aef48c0612905aa88b7553cc3323c

Was working fine on 2018.06:

<AlexDaniel> c: 2018.06,HEAD package Foo { use experimental :pack; sub go() is export { "".encode.unpack("*") }; }; import Foo; go()
<committable6> AlexDaniel, ¦2018.06: «» ¦HEAD(cb2ea93): «Use of the 'unpack' method is experimental; please 'use experimental :pack'␤ in sub go at /tmp/DtKIwcN2IU line 1␤ in block <unit> at /tmp/DtKIwcN2IU line 1␤␤ «exit code = 1»»

⚠⚠⚠ Bisected: (2018-07-18) a847abe

I assigned some people who should know more about it, but anyone please feel free to work on this.

[lizmat]

It appears it's the import that checks for whether unpack is allowed or not. So at least a workaround is the move the use experimental :pack to the scope of the import:

package Foo { sub go() is export { "".encode.unpack("*") }; }; use experimental :pack; import Foo; go()

Continuing ways of fixing this.

EDIT: just having it in the outer scope, is probably why this workaround works.

[jnthn]

Fixed the getlexcaller regression that caused this in MoarVM/MoarVM@ba906c4297

[lizmat]

Test added with Raku/roast@3129a4a708 , can be closed afaiac

[AlexDaniel]

@lizmat why a roast test for an experimental feature?

[lizmat]

FWIW, I just looked to "use experimental :pack' in t/spec and added the test there. It was not the only one. So, if this needs to be moved, many more will need to be moved.