From @AlexDaniel

Code​:
my @​c[2;2] .= new(​:shape(2, 2), <a b>, <c d>)'

Result (2015.12,2016.10)​:
[[1 a] [2 b]]
(1 a 2 b)

Result (2016.11,HEAD)​:
Cannot assign an array of shape 2 2 to an array of shape 2 2
  in block <unit> at /tmp/9MD__1ftfd line 1
«exit code = 1»

Bisectable points to two related commits​:
rakudo/rakudo@1293188
rakudo/rakudo@c5d33a2

Error appeared after the first one, but looked like this​:

Assignment to array with shape 2 2 must provide structured data
  in block <unit> at /tmp/jA3o34pAeI line 1

Actual nonsense in the error message was introduced after the second commit​:

Cannot assign an array of shape 2 2 to an array of shape 2 2
in block <unit> at /tmp/jA3o34pAeI line 1

From @AlexDaniel

Obviously, it is a wrong snippet. Here is the right one​:

my @​c[2;3] .= new(​:shape(2, 2), [1, "a"], [2, "b"])

On 2017-01-04 19​:52​:58, alex.jakimenko@​gmail.com wrote​:

Code​:
my @​c[2;2] .= new(​:shape(2, 2), <a b>, <c d>)'

Result (2015.12,2016.10)​:
[[1 a] [2 b]]
(1 a 2 b)

Result (2016.11,HEAD)​:
Cannot assign an array of shape 2 2 to an array of shape 2 2
in block <unit> at /tmp/9MD__1ftfd line 1
«exit code = 1»

Bisectable points to two related commits​:
rakudo/rakudo@1293188
rakudo/rakudo@c5d33a2

Error appeared after the first one, but looked like this​:

Assignment to array with shape 2 2 must provide structured data
in block <unit> at /tmp/jA3o34pAeI line 1

Actual nonsense in the error message was introduced after the second
commit​:

Cannot assign an array of shape 2 2 to an array of shape 2 2
in block <unit> at /tmp/jA3o34pAeI line 1

From @lizmat

Fixed with d77f9b8 , tests needed

On 5 Jan 2017, at 04​:52, Aleks-Daniel Jakimenko-Aleksejev (via RT) <perl6-bugs-followup@​perl.org> wrote​:

# New Ticket Created by Aleks-Daniel Jakimenko-Aleksejev
# Please include the string​: [perl #​130510]
# in the subject line of all future correspondence about this issue.
# <URL​: https://rt-archive.perl.org/perl6/Ticket/Display.html?id=130510 >

Code​:
my @​c[2;2] .= new(​:shape(2, 2), <a b>, <c d>)'

Result (2015.12,2016.10)​:
[[1 a] [2 b]]
(1 a 2 b)

Result (2016.11,HEAD)​:
Cannot assign an array of shape 2 2 to an array of shape 2 2
in block <unit> at /tmp/9MD__1ftfd line 1
«exit code = 1»

Bisectable points to two related commits​:
rakudo/rakudo@1293188
rakudo/rakudo@c5d33a2

Error appeared after the first one, but looked like this​:

Assignment to array with shape 2 2 must provide structured data
in block <unit> at /tmp/jA3o34pAeI line 1

Actual nonsense in the error message was introduced after the second commit​:

Cannot assign an array of shape 2 2 to an array of shape 2 2
in block <unit> at /tmp/jA3o34pAeI line 1

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

From @zoffixznet

Tests in Raku/roast@1f05be281e

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