a = 3
b
[4, 5].filter(it < 5)
===output===
error: undefined ident: `a` (use `:=` to declare a variable)
    5 | import math
    6 | 
    7 | a = 3
      | ^
error: cannot assign to `a`: expected `void`, not `int literal`
    5 | import math
    6 | 
    7 | a = 3
      |     ^
error: undefined ident: `b`
    5 | import math
    6 | 
    7 | println(b)
      |         ^
error: `println` can not print void expressions
    5 | import math
    6 | 
    7 | println(b)
      | ~~~~~~~~~~
[4]
