Conversion from int does not respect the JS safe range as documented

[okkero]

I am having some trouble working with this library. Conversion from int seems to break down for large numbers, even when the number is within the JS safe range.

Take a look at the following code: https://ellie-app.com/mMqXP4NnLsNa1
The value given to all of those operations is lower than MAX_SAFE_INTEGER, but the result is still not what was put in when going back to string through Int64.

The documentation for Int64.fromInt says it is guaranteed to work for integers in the safe JS range. Yet, this is not the behavior I'm seeing.

Or maybe toSignedString and/or toUnsignedString are broken? I don't know.