edit: Lint some functions which are to be copied for symbolic tests

src/nvim/edit.c

@@ -6074,27 +6074,30 @@ void free_last_insert(void)
 
 #endif
 
-/*
+/// Add character "c" to buffer "s"
- * Add character "c" to buffer "s".  Escape the special meaning of K_SPECIAL
+///
- * and CSI.  Handle multi-byte characters.
+/// Escapes the special meaning of K_SPECIAL and CSI, handles multi-byte
- * Returns a pointer to after the added bytes.
+/// characters.
- */
+///
+/// @param[in]  c  Character to add.
+/// @param[out]  s  Buffer to add to. Must have at least MB_MAXBYTES + 1 bytes.
+///
+/// @return Pointer to after the added bytes.
 char_u *add_char2buf(int c, char_u *s)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
 {
   char_u temp[MB_MAXBYTES + 1];
-  int i;
+  const int len = utf_char2bytes(c, temp);
-  int len;
+  for (int i = 0; i < len; ++i) {
-
-  len = (*mb_char2bytes)(c, temp);
-  for (i = 0; i < len; ++i) {
     c = temp[i];
-    /* Need to escape K_SPECIAL and CSI like in the typeahead buffer. */
+    // Need to escape K_SPECIAL and CSI like in the typeahead buffer.
     if (c == K_SPECIAL) {
       *s++ = K_SPECIAL;
       *s++ = KS_SPECIAL;
       *s++ = KE_FILLER;
-    } else
+    } else {
       *s++ = c;
+    }
   }
   return s;
 }