Incompatibility of Array#[]=

[ksss]

a = []
a[3..4] = 1
p a
#=> CRuby: [nil, nil, nil, 1]
#=> mruby: []

a = []
a[-1..-1] = 1
#=> CRuby: RangeError: -1..-1 out of range
#=> mruby: return 1 and `a` is `[]`

I think, The cause is incompatibility of mruby's mrb_range_beg_len and CRuby's rb_range_beg_len

mruby/src/array.c

Line 803 in bd50273

if (mrb_range_beg_len(mrb, v1, &i, &len, RARRAY_LEN(self))) {

https://github.com/ruby/ruby/blob/78b95b49f8715a4782f5b9bdc4c163e445cdc303/array.c#L1740

I think, We'll need another function same as mrb_range_beg_len if we want to fix this issue and expect no break backward compatibility.

[matz]

The difference is not intended, so I will fix this (and break compatibility).

[ksss]

Thank you for big deciding ✨

[dabroz]

cc #3140