[perl #123776] Binding a variable at BEGIN time doesn't stick aruond for runtime

On Tue, 30 Jan 2018 15:08:38 -0800, [email protected] wrote:
> On Fri, 01 Dec 2017 12:09:05 -0800, [email protected] wrote:
> > Still reproducible (2017.11, HEAD(5929887)), but is supposed to work?
> 
> Don't see any reason why that'd be questionable.
> 
> > On 2015-02-09 17:43:52, [email protected] wrote:
> > > m: my $a; BEGIN { $a := 1; say $a; }; say $a;
> > > rakudo-{parrot,moar} 0cb22e: OUTPUT«1␤(Any)␤»
> > >
> > > m: my $a; BEGIN { $a = 1; say $a; }; say $a; # works with assignment
> > > rakudo-{parrot,moar} 0cb22e: OUTPUT«1␤1␤»
> 
> 
> Another manifestation of the same bug:
> 
> <Zoffix__> m: BEGIN { my $a1 := 42; say $a1; }
> <camelia> rakudo-moar deffe54b8: OUTPUT: «42␤»
> <Zoffix__> m: BEGIN { my $a1 = 42; say $a1; }
> <camelia> rakudo-moar deffe54b8: OUTPUT: «42␤»
> <Zoffix__> m: BEGIN my $a1 = 42; say $a1;
> <camelia> rakudo-moar deffe54b8: OUTPUT: «42␤»
> <Zoffix__> m: BEGIN my $a1 := 42; say $a1;
> <camelia> rakudo-moar deffe54b8: OUTPUT: «(Mu)␤»



Tracked this to Perl6::World.compile_in_context but leaving it there, as it's getting too hard.
Need to gain a few levels first.

The comment in the method reads:
   # Create outer lexical contexts with all symbols visible. Maybe
   # we can be a bit smarter here some day. But for now we just make a
   # single frame and copy all the visible things into it.

So I imagine the binding gets made to this faked out block and never propagates back to the source where all the lexicals were copied from.