Pi : 3.1415  # Error: Cannot assign non-consumable to consumable constant.
pi : 3.1415  # Ok

Cident : Char<A-Za-z_> Char<A-Za-z0-9_>* $0
cident : Cident  # Error: Cannot assign consumable to non-consumable constant.
NewCident : Cident  # Ok

factorial : @n {
    if n <= 0 return 1
    n * factorial(n - 1)
}
Factorial : factorial  # Error: Cannot assign non-consumable to consumable constant.

IsOkay : @{
    Int if $1 > 100 && $1 < 1000 accept
}  # Ok, because the function is a parselet as it calls Cident

_ : "abc"

#---
#ERR:Line 1, column 1: Cannot assign to constant 'Pi', because it must be consumable. Use an identifier starting in lower-case, e.g. 'pi'
#ERR:Line 5, column 1: Cannot assign to constant 'cident' as consumable. Use an identifier starting in upper-case, e.g. 'Cident'
#ERR:Line 12, column 1: Cannot assign to constant 'Factorial', because it must be consumable. Use an identifier starting in lower-case, e.g. 'factorial'
#ERR:Line 18, column 1: Cannot assign to constant '_', because it must be consumable. Use an identifier not starting with '_'.