[perl #128054] [PARSER] In a string enclosed in parens, a {}-interpolation can't access the topic $_ of a statement modifier

On Tue, 03 Oct 2017 09:38:23 -0700, [email protected] wrote:
> On Mon, 02 Oct 2017 19:08:27 -0700, [email protected] wrote:
> > Also worth taking a look at
> > https://rt.perl.org/Ticket/Display.html?id=126569
> > 
> > On 2017-09-29 14:06:58, [email protected] wrote:
> > > On Sun, 28 May 2017 00:08:18 -0700, [email protected] wrote:
> > > > This bug is still present in
> > > >
> > > > This is Rakudo version 2017.05-134-g0c5fe56cc built on MoarVM
> > > > version
> > > > 2017.05-25-g62bc54e9
> > > > implementing Perl 6.c.
> > >
> > >
> > > OK, keeping in mind that I have entirely, absolutely no idea what I
> > > am
> > > doing...
> > >
> > > I figured out that the block inside the string inside the parens is
> > > being annotated
> > > to a statement ID one greater than that of the whole statement_mod,
> > > which means
> > > it doesn't get "migrated". I also figured out that it seems to be the
> > > case that
> > > no blocks from inside the predicate of the for/given appear in the
> > > list considered
> > > for migration. I don't know if the annotation is correct or not, and
> > > I don't know
> > > if there is some contorted syntax that could put a block in the list
> > > of considered
> > > items for migration which would be erroneously migrated, but simply
> > > changing
> > > make_topic_block_ref to also grab all in_stmt_mod blocks with a
> > > statement ID higher
> > > than the one it is handed seems to pass all spectests and "fix" this
> > > problem.
> > >
> > > Resulting in the following one-character patch (drumroll please):
> > >
> > > diff --git a/src/Perl6/Actions.nqp b/src/Perl6/Actions.nqp
> > > index 36fa59b2b..6576f61b7 100644
> > > --- a/src/Perl6/Actions.nqp
> > > +++ b/src/Perl6/Actions.nqp
> > > @@ -8953,7 +8953,7 @@ class Perl6::Actions is HLL::Actions does
> > > STDActions {
> > > $*W.pop_lexpad();
> > > if nqp::defined($migrate_stmt_id) {
> > > migrate_blocks($*W.cur_lexpad(), $block, -> $b {
> > > - !$b.ann('in_stmt_mod') && ($b.ann('statement_id') //
> > > -1) == $migrate_stmt_id
> > > + !$b.ann('in_stmt_mod') && ($b.ann('statement_id') //
> > > -1) >= $migrate_stmt_id
> > > });
> > > }
> > > ($*W.cur_lexpad())[0].push($block);
> > >
> > > Now, all that said, I cannot begin to properly emphasize the massive
> > > extent of the heck of which I do not know here.
> > >
> > > So, this is either the right fix, or a very wrong fix which might
> > > just
> > > break things in a way
> > > roast test writers are just not twisted and deviant enough to think
> > > of, or a fix that doesn't
> > > catch derivative cases, or...
> > >
> > > Other cases tested with this patch:
> > >
> > > $ perl6 -e 'say ("{$_}") given <aa bb>'
> > > aa bb
> > > $ perl6 -e 'say ("{$_}") if True given <aa bb>'
> > > aa bb
> > > $ perl6 -e 'say ("{$_}") if ({True}) given <aa bb>'
> > > aa bb
> > > $ perl6 -e 'say ("{$_}") if ("{True}") given <aa bb>'
> > > aa bb
> > > $ perl6 -e 'say ("{$_}") if "{True}" given <aa bb>'
> > > aa bb
> > > $ perl6 -e 'say ("{$_}") if "{so $_}" given <aa bb>'
> > > aa bb
> > > $ perl6 -e 'say ("{$_}") if ("{$_ ~~ /bb/ ?? q|1| !! q|| }") for <aa
> > > bb> '
> > > bb
> > > $ perl6 -e 'say ("{$_}") for ("{$_}" for <aa bb>)'
> > > aa
> > > bb
> > > $ perl6 -e 'my $a = 13; say ("{$_}") for {my $a = 42; ("{$a}" for <aa
> > > bb> )}()'
> > > 42
> > > 42
> 
> 
> I'm still running with that patch installed and yes, it does seem to
> help the example in 126569 to work.
> 


Thank you for the report. This is now fixed.

Fix:  https://github.com/rakudo/rakudo/commit/1ee89b54074e80c
Test: https://github.com/perl6/roast/commit/2f2998733a2d8132c