Weird behavior of multiple assignment (a, b, *c = [])

[naclyhara]

While trying CRuby's basictest/test.rb with mruby (6c299a), I found this test fails on mruby:

a,b,*c = []; test_ok([a,b,c] == [nil,nil,[]]) 

Here is how to reproduce the issue.

p [1, 2, 3]  # Some random code

a,b,*c = []
p [a, b, c]
# cruby: [nil, nil, []]
# mruby: [[1, 2, 3], [[1, 2, 3]], []]    # a and b has unexpected value

These tests also fail:

a,b,*c = [1]; test_ok([a,b,c] == [1,nil,[]])
a,b,*c = [nil]; test_ok([a,b,c] == [nil,nil,[]])
a,b,*c = [[]]; test_ok([a,b,c] == [[],nil,[]])