We will not accept floats because `123.123` is a float literal,
but `123 .123` is a int literal followed by a class called `123`.
This could be confusing so it will not be accepted.

Ints can have leading zeros, like `0123`, but this is not guarranteed by
the rust compiler to always work, which could cause future errors.
An example would be truncating `001` to `1`.

This outputs exactly what is written, which is the obvious behaviour

Previous verison was not using nightly, causing errors in the automated
test that are using nightly