From @labster

labster​: r​: sub foo { X​::IO​::Dir.new(path=>'a', os-error=>'b').fail }; my
@​a = foo(); 1;
camelia​: rakudo b2072f​: ( no output )
labster​: r​: sub foo { X​::IO​::Dir.new(path=>'a', os-error=>'b').fail }; my
@​a := foo(); 1;
camelia​: rakudo b2072f​: OUTPUT«Failed to get the directory contents of 'a'​:
b␤ in method sink at src/gen/CORE.setting​:10169␤ in method BUILDALL at
src/gen/CORE.setting​:801␤ in method bless at src/gen/CORE.setting​:743␤ in
method new at src/gen/CORE.setting​:728␤ in method new at src/gen/CORE.…
labster​: r​: sub foo { X​::IO​::Dir.new(path=>'a', os-error=>'b').fail }; my
$a := foo(); 1;
camelia​: rakudo b2072f​: ( no output )

Unless someone tells me this is not a bug -- but it seems like this would
be the correct approach when loading a lazy list.

From @usev6

AFAIU this looks fine now​:

$ perl6 -e 'sub foo { X​::IO​::Dir.new(path=>"a", os-error=>"b").fail }; my @​a := foo(); 1'
Type check failed in binding; expected 'Positional' but got 'Failure'
  in any bind_error at src/vm/moar/Perl6/Ops.nqp​:224
  in block <unit> at -e​:1

The Failure X​::IO​::Dir is no longer thrown, but the code dies because @​a cannot be bound to a non Positional.

If I add a second element on the rhs of the binding, the code runs fine​:

$ ./perl6 -e 'sub foo { X​::IO​::Dir.new(path=>"a", os-error=>"b").fail }; my @​a := foo(), 42; say @​a.perl'
(Failure.new(exception => X​::IO​::Dir.new(path => "a", os-error => "b")), 42)

I'd vote for 'closable with tests'.

@usev6 - Status changed from 'new' to 'open'

From @zoffixznet

Tests​: Raku/roast@5cd8dff2292c1c4cab83f0b5

@zoffixznet - Status changed from 'open' to 'resolved'