bug#66912: With `require', the byte compiler reports the wrong file for errors.

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>> I understand that, but I don't think it explains why you think it's
>> a problem.  E.g. when you're in the debugger, you can see the stack
>> trace which tells you we're loading A, so you don't need to be told
>> "while loading A" in the error message.
> OK, I see what you mean.  I took it for granted that the message should
> be the same, regardless of whether it is reported by a debugger or by
> the error handler.

AFAIK the debugger does not emit the "error message" at all, it shows
the error object instead, so it's already different.

And the full info would readily be available from `Vloads_in_progress_at_error`.

>> I'm just describing the way I see it: I personally don't have a good
>> intuition of how/when it could misbehave nor how to work around such
>> cases, whereas I very much do for the approach I propose and AFAICT it's
>> not just because I proposed it but it's because it follows
>> a known pattern, so I expect the same will hold for other coders.
> Experience with byte-compile-form-stack suggests it won't misbehave.
> Its simplicity should make it easy to think through.

AFAICT

    (equal (error-message-string ERROR-OBJECT)
           (error-message-string ERROR-OBJECT))

will not always return t, which I'd consider as a misbehavior.

I don't mean that we need to fix it.  Just that that there *will* be
misbehaviors, because we use a low-tech approach which stashes the info
in a global variable.


        Stefan