struct: rework stype_handle change.

The change which allows stype_handle to recognize struct
instances, and obtain their type, has some possibly unwanted
ramifications, since the function is widely used.
Let's refactor things so that, for now, only the
struct_type_name function takes advantage of this flexibility.

* struct.c (stype_handle_impl): New static function, copy of
stype_handle, but taking an obj_ok Boolean argument to
indicate whether an object instance is an acceptable argument,
whose type should be fetched.
(stype_handle): Now a wrapper around stype_handle_impl passing
nil for the obj_ok argument.
(stype_handle_obj): New static function. Passes t for the
ok_obj argument of stype_handle_impl.
(struct_type_name): Call stype_handle_obj instead of
stype_handle.
(super): Take advantage of stype_handle_obj to reduce code.

* txr.1: Update documentation of struct-type-name, and improve
that of super.

1 files changed, 20 insertions, 17 deletions

diff --git a/txr.1 b/txr.1
index 9d5ae2b1..c36be80c 100644
--- a/txr.1
+++ b/txr.1
@@ -28993,39 +28993,42 @@ returned by
 
 .coNP Function @ struct-type-name
 .synb
-.mets (struct-type-name << type )
+.mets (struct-type-name << type-or-struct )
 .syne
 .desc
 The
 .code struct-type-name
-function returns the symbol which serves as the name of
-.metn type ,
-which must be either a struct type object (such as the return value of
+function determines a structure type from the
+.meta type-or-struct
+and returns that structure type's symbolic name.
+
+The
+.meta type-or-struct
+argument must be either a struct type object (such as the return value of
 a successful lookup via
 .codn find-struct-type ),
-or else a struct type name.
+a symbol which names a struct type,
+or else a struct instance.
 
 .coNP Function @ super
 .synb
-.mets (super << type )
+.mets (super >> [ type-or-struct ])
 .syne
 .desc
 The
 .code super
-function returns the struct type object which is the
-supertype of
-.metn type ,
-or returns
+function determines a structure type from the
+.meta type-or-struct
+and returns the struct type object which is
+the supertype of that type, or else
 .code nil
-if
-.meta type
-has no supertype.
+if that type has no supertype.
 
 The
-.meta type
-argument must be either a struct type object, a
-a symbol which names a struct type (which is resolved to that type),
-or else a structure instance (which is resolved to its structure type).
+.meta type-or-struct
+argument must be either a struct type object,
+a symbol which names a struct type,
+or else a struct instance.
 
 .coNP Function @ make-struct
 .synb