Subset type used in Signatures fails with errors

[cono]

20:11 < moritz> it's a bug in the optimizer

The Problem

20:08 < cono> m: module A { my subset CAT is export of Code where { .arity == 2 } }; import A; sub xz(CAT :$c) { say $c(3, 5) }; xz(c => * <=> *)
20:08 <+camelia> rakudo-moar 1447f41: OUTPUT: «===SORRY!===␤Cannot look up attributes in a A::CAT type object␤»

Expected Behavior

subset type should work in signatures and class attributes.

Actual Behavior

fails with error: Cannot look up attributes in a CAT type object

Steps to Reproduce

20:12 < moritz> m: subset CAT of Code; sub xz(CAT $c) { };
20:12 <+camelia> rakudo-moar 1447f41: OUTPUT: «===SORRY!===␤Cannot look up attributes in a CAT type object␤»

Environment

• Operating system: Gentoo
• Compiler version (perl6 -v):
  perl6 -v
  This is Rakudo version 2018.04.1-37-g1447f41e6 built on MoarVM version 2018.04-39-gc702f4c66
  implementing Perl 6.c.

[moritz]

This is the backtrace I get with --ll-exception:

   at gen/moar/Perl6-Optimizer.nqp:2308  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:optimize-param-typecheck)
 from gen/moar/Perl6-Optimizer.nqp:2276  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_children)
 from gen/moar/Perl6-Optimizer.nqp:2040  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_var)
 from gen/moar/Perl6-Optimizer.nqp:2218  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_children)
 from gen/moar/Perl6-Optimizer.nqp:2230  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_children)
 from gen/moar/Perl6-Optimizer.nqp:946  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_block)
 from gen/moar/Perl6-Optimizer.nqp:2221  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_children)
 from gen/moar/Perl6-Optimizer.nqp:2230  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_children)
 from gen/moar/Perl6-Optimizer.nqp:2230  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_children)
 from gen/moar/Perl6-Optimizer.nqp:946  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:visit_block)
 from gen/moar/Perl6-Optimizer.nqp:920  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Optimizer.moarvm:optimize)
 from src/Perl6/Compiler.nqp:47  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Compiler.moarvm:optimize)
 from gen/moar/stage2/NQPHLL.nqp:1845  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:execute_stage)
 from gen/moar/stage2/NQPHLL.nqp:1878  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:run)
 from gen/moar/stage2/NQPHLL.nqp:1881  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:)
 from gen/moar/stage2/NQPHLL.nqp:1867  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:compile)
 from gen/moar/stage2/NQPHLL.nqp:1567  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:eval)
 from gen/moar/stage2/NQPHLL.nqp:1822  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:evalfiles)
 from gen/moar/stage2/NQPHLL.nqp:1747  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:command_eval)
 from src/Perl6/Compiler.nqp:42  (/home/moritz/p6/rakudo/install/share/nqp/lib/Perl6/Compiler.moarvm:command_eval)
 from gen/moar/stage2/NQPHLL.nqp:1673  (/home/moritz/p6/rakudo/install/share/nqp/lib/NQPHLL.moarvm:command_line)
 from gen/moar/main.nqp:47  (/home/moritz/p6/rakudo/install/share/perl6/runtime/perl6.moarvm:MAIN)
 from gen/moar/main.nqp:38  (/home/moritz/p6/rakudo/install/share/perl6/runtime/perl6.moarvm:<mainline>)
 from <unknown>:1  (/home/moritz/p6/rakudo/install/share/perl6/runtime/perl6.moarvm:<main>)
 from <unknown>:1  (/home/moritz/p6/rakudo/install/share/perl6/runtime/perl6.moarvm:<entry>)

[AlexDaniel]

Output on all releases: https://gist.github.com/8280e0a1953d48a3308d417ca3aeed69

Bisected to these commits:
43b9c82
f8c2b55 (merge commit)
426a39a
ae69708
d74010b (merge commit)

<moritz> the first one looks suspect
<moritz> it touches subsets and the optimizer

[moritz]

I suspect that this: 43b9c82#diff-deae5f68054ef8116f04d6cb78bc4395R8906 needs another condition that checks if $_ is definite.