List patterns incorrectly translated

[nordlander]

Acton Version

0.24.1.20250226.13.5.28

Steps to Reproduce and Observed Behavior

Compiling

def fun(x):
    [a, b] = x.split(":")

leads to a crash in the deactorizer pass, apparently because of a missing witness parameter in the type-checker output.

Expected Behavior

Should compile and be equivalent to

def fun(x):
    temp = x.split(":")
    a = temp[0]
    b = temp[1]