fish version 3.3.1.

Playing with set builtin I stumbled upon a sigsegv using set --show var

Example script.fish:

#!/usr/bin/env fish

set -l local_var 'on'
set --show local_var

sh -c 'env HOME=$(mktemp -d) fish'
chmod +x script.fish
./script.fish

gives:
terminated by signal SIGSEGV

Playing abit further I realized that it is dependant of the LANG variable (since it happens when setting it to fr_FR.utf8 although it is not reproductible with en_US.utf8 neither fr_FR)