source-properties versus set-source-properties!

[Kevin Ryde]

In guile 1.6.3 built on a recent i386 debian, it seems
source-properties and set-source-properties! don't really cooperate.

For instance a file foo.scm,

        (define x '(1 2 3))
        (define y '(4 5 6))

        (set-source-properties! y (source-properties x))

        (display (source-properties x)) (newline)
        (display (source-properties y)) (newline)

run with "guile --debug -s foo.scm" prints

   ((breakpoint . #f) (line . 0) (column . 11) (filename . foo.scm))
   ()

whereas I hoped it would print two lines the same, having copied the
properties from x onto y.


Nosing around srcprops.c, I guess set-source-properties! will put an
alist in the hash table, but source-properties won't return that,
instead always returning '() for anything except an srcprops object.

If source-property and set-source-property! are to be believed then I
guess either an srcprops or an alist is allowed in the hash, perhaps
on that basis source-properties should simply return verbatim what it
finds in the hash if it's not an srcprops.  Ie. "return SCM_EOL" would
become "return p".