Issue 4365: non-member unsmob<T> replaces T::unsmob and T::is_smob

Hide Smob_base<>::is_smob() to prevent the misleading situation of
D::is_smob(S) returning true when S represents an ancestor of D rather
than a D.  This issue was previously worked around by overriding
is_smob in several derived smob classes; that is no longer needed.

LY_ASSERT_SMOB() now returns a smob pointer.  This is not used yet,
but is available for future use to avoid unsmobbing twice.

Smob_base<>::smob_p() is hidden because there doesn't seem to be a
need for it to be public.

Files in lily/include were edited by hand.  Files in lily itself were
processed with the following sed script.

s/\([A-Za-z_]\+\)::derived_unsmob/unsmob<\1>/g
s/derived_unsmob *<\([A-Za-z_]\+\)>/unsmob<\1>/g
s/\([A-Za-z_]\+\)::unsmob/unsmob<\1>/g
s/\([A-Za-z_]\+\)::is_smob/unsmob<\1>/g
s/Input \*\([A-Za-z_]\+\) = unsmob /Input *\1 = unsmob<Input> /g
s/LY_ASSERT_SMOB (\([^)]*\))$/LY_ASSERT_SMOB (\1);/g

1 files changed, 3 insertions, 3 deletions

diff --git a/lily/item-scheme.cc b/lily/item-scheme.cc
index 24ccf5bf0d..48f3218f22 100644
--- a/lily/item-scheme.cc
+++ b/lily/item-scheme.cc
@@ -25,7 +25,7 @@ LY_DEFINE (ly_item_p, "ly:item?",
            1, 0, 0, (SCM g),
            "Is @var{g} an @code{Item} object?")
 {
-  Grob *me = Grob::unsmob (g);
+  Grob *me = unsmob<Grob> (g);
   bool b = dynamic_cast<Item *> (me);
   return ly_bool2scm (b);
 }
@@ -37,7 +37,7 @@ LY_DEFINE (ly_item_break_dir, "ly:item-break-dir",
            " @code{1}@tie{}beginning of line.")
 {
   LY_ASSERT_SMOB (Item, it, 1);
-  Item *me = Item::unsmob (it);
+  Item *me = unsmob<Item> (it);
   return scm_from_int (me->break_status_dir ());
 }
 
@@ -47,7 +47,7 @@ LY_DEFINE (ly_item_get_column, "ly:item-get-column",
            " associated with this @code{Item}.")
 {
   LY_ASSERT_SMOB (Item, it, 1);
-  Item *me = Item::unsmob (it);
+  Item *me = unsmob<Item> (it);
 
   if (Paper_column *col = me->get_column ())
     return col->self_scm ();