From @smls

Calling .gist on the Sub objects on of built-in subroutines/operators, causes a strange warning to be printed (in Rakudo 2015.01-156-g5ba2c86 with MoarVM 2015.01-69-g5bbfd1a)​:

  > say &map.gist
  use of uninitialized value $name of type Any in string context in block <unit> at <unknown file>​:1
 
  sub map (Any |) { #`(Sub|44490920) ... }
  > say &postcircumfix​:<[ ]>.gist
  use of uninitialized value $name of type Any in string context in block <unit> at <unknown file>​:1
 
  sub postcircumfix​:<[ ]> (Any |) { #`(Sub|45073152) ... }

The problem does not occur with custom subs​:

  >say (sub foo {}).gist
  sub foo () { #`(Sub|56973008) ... }

From @Mouq

Fixed in Rakudo commit​:

commit bb3a3df1abe27ae53e8f299b579edfcd89710a76
Author​: Mouq <alexmoquin@​gmail.com>
Date​: Mon Feb 23 00​:35​:58 2015 -0500

  Don't warn when gisting &map, &grep, etc.; RT #​123895

  The issue was that these subs had signatures with an unnamed "|"
  parameter in them, and a check was never made to see if "|" or "\"
  parameters had names.

Tests added to S06-signature/introspection.t in Roast commit​:

commit 317b088b1920c6a90692de536a2f78cdb55ffdc7
Author​: Mouq <alexmoquin@​gmail.com>
Date​: Mon Feb 23 00​:58​:02 2015 -0500

  Add tests for RT #​123895

Closing as resolved :)

On Fri Feb 20 08​:10​:13 2015, smls75@​gmail.com wrote​:

Calling .gist on the Sub objects on of built-in subroutines/operators,
causes a strange warning to be printed (in Rakudo 2015.01-156-g5ba2c86
with MoarVM 2015.01-69-g5bbfd1a)​:

say &map.gist
use of uninitialized value $name of type Any in string context in
block <unit> at <unknown file>​:1

sub map (Any |) { #`(Sub|44490920) ... }

say &postcircumfix​:<[ ]>.gist
use of uninitialized value $name of type Any in string context in
block <unit> at <unknown file>​:1

sub postcircumfix​:<[ ]> (Any |) { #`(Sub|45073152) ... }

The problem does not occur with custom subs​:

say (sub foo {}).gist
sub foo () { #`(Sub|56973008) ... }

The RT System itself - Status changed from 'new' to 'open'

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