bug#24749: Making sure syntax-propertize is called

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Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> It seems that the only(?) use case for a nil `parse-sexp-lookup-properties` 
>> is
>> to set it to nil dynamically in specialized lookup code for performance
>> reasons. Such code does let-bind it to nil already.
>
> I can't remember binding it to nil for performance reasons (tho maybe
> that's the reason behind yasnippet.el's case), but we do let-bind it
> temporarily to nil in a few cases as a hackish way to have a "different
> view" of the buffer which happens to fit our needs.  E.g. this is done
> in font-latex.el and sm-c-mode.el.

A "different view" of the buffer is the reason for yasnippet.el's use of
it too: it's parsing braces in "snippet syntax", which is not related to
the major mode's syntax.  (Really, parsing of the snippet syntax should
be done in a separate buffer to remove the need for this, but the
parsing code is intertwined with the evaluation of lisp in some snippet
constructs, so it's tricky to do that.)