bug#15778: 24.3; cperl-mode causes emacs to lock up

[Nathan Trapuzzano]

Eli Zaretskii <eliz@gnu.org> writes:

> Is it safe to assume that a 'syntax-type' property will never cover
> exactly one buffer position?

I think the question is actually whether it's safe to assume that
font-lock-mode will never pass cperl's font-lock function a point (BEG)
on a line whose first position is the beginning of a `multiline'
`syntax-type' property.  (That's a mouth full.)

I can see why such an assumption might be made.  So far as I can tell,
the multiline property always begins at the position immediately
following certain operators.  Obviously, this can't ever be a position
satisfying (bolp), since newline is no such operator.

However, in this case, we're killing the line where the multiline
property begins, and so as cperl goes about refontifying, it appears
that the multiline property does in fact begin a line.

So in the end, no, I don't think it's a safe assumption, at least not
until _after_ fontification.

> (I have no idea why the defalias is needed to trigger the bug.)

Indeed.