Self-referential objects break decoders

If an object is passed in that refers to itself (like the express req object), an infinite loop occurs.

Smallest reproducible example:

const { string } = require('decoders');

// Take any decoder and pass in some self-referential object
const req = {};
req.myself = req;

console.log(string(req)); // <--- RangeError: Maximum call stack size exceeded

[nvie]

Default error messages are kinda broken when this large anyways.

If you want more succinct error messages, try using guard(..., { style: 'simple' }) instead of just the default guard(...). That will not echo back the input object, and just describe where the error is. That won’t help you with this issue, but may help reduce your error messages in case of large objects.

[sfarthin]

Thanks for the good work on this library, its an essential tool when working with types in JS/TS.