2%int63
     : int
(2 + 2)%int63
     : int
2
     : int
9223372036854775807
     : int
2 + 2
     : int
2 + 2
     : int
     = 4
     : int
     = 37151199385380486
     : int
The command has indeed failed with message:
int63 are only non-negative numbers.
The command has indeed failed with message:
overflow in int63 literal: 9223372036854775808
2
     : nat
2%int63
     : int
t = 2%i63
     : int
t = 2%i63
     : int
2
     : nat
2
     : int