Double substitution issue

[William Entriken]

This behavior is different in zsh and bash, and maybe bash behavior is a
bug.

# Test case

touch 1 2 3
cat > script.sh <<EOL
from=1
to=3
ls {$from..$to}
EOL
chmod a+x script.sh

bash ./script.sh

zsh ./script.sh

# Expected

Both list files 1, 2, 3

# Actual

zsh passes.

Bash fails the chained substitution with:

ls: {1..3}: No such file or directory