casing: don’t assume letters are *either* upper- or lower-case (bug#24603)

A compatibility digraph characters, such as Dž, are neither upper- nor
lower-case.  At the moment however, those are reported as upper-case¹
despite the fact that they change when upper-cased.

Stop checking if a character is upper-case before trying to up-case it
so that title-case characters are handled correctly.  This fixes one of
the issues mentioned in bug#24603.

¹ Because they change when converted to lower-case.  Notice an asymmetry
  in that for a character to be considered lower-case it must not be
  upper-case (plus the usual condition of changing when upper-cased).

* src/buffer.h (upcase1): Delete.
(upcase): Change to upcase character unconditionally just like downcase
does it.  This is what upcase1 was.

* src/casefiddle.c (casify_object, casify_region): Use upcase instead
of upcase1 and don’t check !uppercasep(x) before calling upcase.

* src/keyboard.c (read_key_sequence): Don’t check if uppercase(x), just
downcase(x) and see if it changed.

* test/src/casefiddle-tests.el (casefiddle-tests--characters,
casefiddle-tests-casing): Update test cases which are now passing.

1 files changed, 9 insertions, 9 deletions

diff --git a/src/buffer.h b/src/buffer.h
index 4a23e4fdd2e..f53212e3120 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -1365,28 +1365,28 @@ downcase (int c)
   return NATNUMP (down) ? XFASTINT (down) : c;
 }
 
-/* True if C is upper case.  */
-INLINE bool uppercasep (int c) { return downcase (c) != c; }
-
-/* Upcase a character C known to be not upper case.  */
+/* Upcase a character C, or make no change if that cannot be done. */
 INLINE int
-upcase1 (int c)
+upcase (int c)
 {
   Lisp_Object upcase_table = BVAR (current_buffer, upcase_table);
   Lisp_Object up = CHAR_TABLE_REF (upcase_table, c);
   return NATNUMP (up) ? XFASTINT (up) : c;
 }
 
+/* True if C is upper case.  */
+INLINE bool uppercasep (int c)
+{
+  return downcase (c) != c;
+}
+
 /* True if C is lower case.  */
 INLINE bool
 lowercasep (int c)
 {
-  return !uppercasep (c) && upcase1 (c) != c;
+  return !uppercasep (c) && upcase (c) != c;
 }
 
-/* Upcase a character C, or make no change if that cannot be done.  */
-INLINE int upcase (int c) { return uppercasep (c) ? c : upcase1 (c); }
-
 INLINE_HEADER_END
 
 #endif /* EMACS_BUFFER_H */