Array.splice insists on flattening the replacement

[DarthGandalf]

The Problem

I have a 2d array (array of arrays), and I want to insert a new row to it.

my @map = [[11, 12], [31,32]];
my @newrow = [21, 22];
@map.splice(1, 0, @newrow);

Expected Behavior

I want @map to look like this:

[
    [11, 12],
    [21, 22],
    [31, 32]
]

Actual Behavior

@map will now look like this:

[
    [11, 12],
    21,
    22,
    [31, 32]
]

I tried to pass [[[[@newrow]]]] to .splice(), tried to pass $@newrow, without any difference. The only workaround I found is this:

@map.splice(1, 0, 'dummy');
@map[1] = @newrow;

Environment

• Operating system: Gentoo Linux, amd64
• Compiler version (rakudo -v or raku -v): v2023.10

[ab5tract]

It took a minute (longer than it should have, in retrospect) but I think I have a way to resolve this without breaking any existing splice contracts.

my @a = [1, 2, 3];
@a.splice(1, 1, [2, 2]) :preserve;
dd @a; # [1, [2, 2], 3

Note that :preserve is just the best I've been able to come up with so far. Suggestions welcome.