Bad enumeration of script errors

[roconnor-blockstream]

elements/src/script/script_error.h

Line 87 in 20c5630

// ELEMENTS:

has incorrectly inserted new Elements errors into this enumeration. All the new elements errors need to go before SCRIPT_ERR_ERROR_COUNT, which isn't actually a real error. Then SCRIPT_ERR_LAST needs to be reset to SCRIPT_ERR_ERROR_COUNT, as it originally was.

AFAICT the only consequences of this error are for the fuzzer.

I'm not sure that having both SCRIPT_ERR_LAST and SCRIPT_ERR_ERROR_COUNT makes sense, but that is how it is in Bitcoin at the moment.

cc @uncomputable

[uncomputable]

The error exists on master: https://github.com/ElementsProject/elements/blob/master/src/script/script_error.h#L85

[uncomputable]

This fuzz test is the only place where SCRIPT_ERR_ERROR_COUNT is used. SCRIPT_ERR_LAST is not used at all.

I think it is safest to keep both errors in case Bitcoin Core starts using either in the future.