if True, () -> log "hello"
if! True, () => print! "hello"
# if True, () => print! "hello" # this should cause a type error
if True, do:
_x = "aaa" + input!() # this should cause an effect error
print! "hello" # this should cause an effect error
f x: Int = log x
g x: Int = print! x # this should cause an effect error
echo = print! # this should be an effect error
_echo = # this is OK
print! 1
log