Re: translation-type? vs. backend-type?

[Lukas-Fabian Moser]

Hi David,
> > Ok, so then I remain unclear as to why the original code seemingly
> > worked with 2.12. But at the end of the day, I don't care that much:
> > 'translation-type it is then, for what should be a \set'table context
> > property.
> I repeat:
>
> > > the change flagging the preexisting problem may possibly be
> > >
> > > commit e44bc2cc48f9fb714603bdb5f8db532d55374087
> > > Author: Neil Puttock <n.puttock@gmail.com>
> > > Date:   Thu Apr 30 20:29:09 2009 +0100
> > >
> > >       Add type-checking to \tweak.
> > >
> > > in version 2.13.1

Sorry for being thick - the use of the word \tweak confused me.

I do not have the old development versions available, so my manual 
bisecting is very much on the coarse side. But I can confirm that:

For the following (WRONG!) definition of a context property

#(set-object-property! 'myprop 'backend-type? integer?)
#(set-object-property! 'myprop 'backend-doc "test property")

(A) LilyPond 2.12.3 complains about \set Staff.myprop = 42 but executes 
it (the property can be retrieved afterwards).
(B) LilyPond 2.12.3 does NOT complain about
  \context Staff {
    \applyContext
    #(lambda (ctx)
       (ly:context-set-property! ctx 'myprop 84))
  }
(and executes it).

LilyPond 2.14.0 still behaves like 2.12.3

LilyPond 2.14.2 complains about (A) and (B), but executes the 
assignments nevertheless.

LilyPond 2.16.2 still behaves like 2.14.2

LilyPond 2.18.0 complains about (A) and (B) and refuses to execute the 
assignments.

And of course, using a correct definition (using 'translation-type?), 
nothing changes between 2.12.3 and 2.22.0.


Code used for testing:

\version "2.12"

#(set-object-property! 'myprop 'backend-type? integer?)
#(set-object-property! 'myprop 'backend-doc "test property")

#(define show_myprop
  (lambda (ctx)
     (let ((myprop-ctx (ly:context-property-where-defined ctx 'myprop)))
       (format #t "Context: ~a\n" myprop-ctx)
       (if (ly:context? myprop-ctx)
           (format #t "myprop value: ~a\n\n"
                   (ly:context-property myprop-ctx 'myprop))))))


{
  \set Staff.myprop = 42
  c'4
  \applyContext #show_myprop

  c'4
  \context Staff {
    \applyContext
    #(lambda (ctx)
       (ly:context-set-property! ctx 'myprop 84))
  }
  c'4
  \applyContext #show_myprop
}

Lukas