$ set -x
$ c file
+ unalias c
+ alias c=crystal file
bash: alias: file: not found
$ set +x

alias usecrystal="alias c=crystal"
alias usecargo="alias c=cargo"

alias c="crystal"
alias crystal="alias c=crystal"
alias cargo="alias c=cargo"

alias c="command crystal"
alias crystal='alias c="command crystal"'
alias cargo='alias c="command cargo"'