:{ } sometimes constructs a Block

[zoffixznet]

Seems to me there's no ambiguity between object hash and Block constructor and so you should always get a Hash or syntax/odd-number-of-items errors instead:

https://irclog.perlgeek.de/perl6-dev/2018-02-23#i_15851491

18:48 	Zoffix 	m: dd :{:$_}
18:48 	camelia 	rakudo-moar 6006e2f63: OUTPUT: «-> ;; $_? is raw { #`(Block|59930128) ... }␤»
18:48 	Zoffix 	This is a bug, innit? That shouldn't ever be a Block
18:48 		m: dd :{;}
18:48 	camelia 	rakudo-moar 6006e2f63: OUTPUT: «-> ;; $_? is raw { #`(Block|63574576) ... }␤»

TimToady 	looks kinda like a bug to me; the $_ criterion was only supposed to be for disambiguating bare {} in cases where it's obviously intened as a block, like in: map { $_ => 1 }, ...

[kjkuan]

I happened to discover this bug last night and exploited it for my purpose:

multi sub val(Block:D $c, :$val-or-fail) { $c().flat>>.Str.Slip }

my @a = << arg2 "arg 3" >>;
dd <<arg1 :{@a} arg4>>;  # ("arg1", "arg2", "arg 3", "arg4")

The idea is to have something similar to how "${array[@]}" is expanded in Bash, which seems to be impossible without this bug + the above hack...