patch 8.2.0855: GUI tests fail because the test doesn't use a modifier

Problem:    GUI tests fail because the test doesn't use a modifier.
Solution:   Add "\{xxx}" to be able to encode a modifier.
diff --git a/src/gui_mac.c b/src/gui_mac.c
index b048375..1ca2d56 100644
--- a/src/gui_mac.c
+++ b/src/gui_mac.c
@@ -4755,8 +4755,7 @@
 	char_u	    *p_actext;
 
 	p_actext = menu->actext;
-	key = find_special_key(&p_actext, &modifiers, FALSE, FALSE, FALSE,
-								   TRUE, NULL);
+	key = find_special_key(&p_actext, &modifiers, FSK_SIMPLIFY, NULL);
 	if (*p_actext != 0)
 	    key = 0; // error: trailing text
 	// find_special_key() returns a keycode with as many of the
diff --git a/src/highlight.c b/src/highlight.c
index 7a7e537..9da87f2 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -1412,8 +1412,7 @@
 		 */
 		for (p = arg, off = 0; off < 100 - 6 && *p; )
 		{
-		    len = trans_special(&p, buf + off, FALSE, FALSE,
-								   TRUE, NULL);
+		    len = trans_special(&p, buf + off, FSK_SIMPLIFY, NULL);
 		    if (len > 0)	    // recognized special char
 			off += len;
 		    else		    // copy as normal char
diff --git a/src/misc2.c b/src/misc2.c
index 678b73c..61c997d 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -2703,20 +2703,17 @@
 trans_special(
     char_u	**srcp,
     char_u	*dst,
-    int		keycode,    // prefer key code, e.g. K_DEL instead of DEL
-    int		in_string,  // TRUE when inside a double quoted string
-    int		simplify,	// simplify <C-H> and <A-x>
-    int		*did_simplify)  // found <C-H> or <A-x>
+    int		flags,		// FSK_ values
+    int		*did_simplify)  // FSK_SIMPLIFY and found <C-H> or <A-x>
 {
     int		modifiers = 0;
     int		key;
 
-    key = find_special_key(srcp, &modifiers, keycode, FALSE, in_string,
-						       simplify, did_simplify);
+    key = find_special_key(srcp, &modifiers, flags, did_simplify);
     if (key == 0)
 	return 0;
 
-    return special_to_buf(key, modifiers, keycode, dst);
+    return special_to_buf(key, modifiers, flags & FSK_KEYCODE, dst);
 }
 
 /*
@@ -2764,24 +2761,23 @@
 find_special_key(
     char_u	**srcp,
     int		*modp,
-    int		keycode,	// prefer key code, e.g. K_DEL instead of DEL
-    int		keep_x_key,	// don't translate xHome to Home key
-    int		in_string,	// TRUE in string, double quote is escaped
-    int		simplify,	// simplify <C-H> and <A-x>
+    int		flags,		// FSK_ values
     int		*did_simplify)  // found <C-H> or <A-x>
 {
     char_u	*last_dash;
     char_u	*end_of_name;
     char_u	*src;
     char_u	*bp;
+    int		in_string = flags & FSK_IN_STRING;
     int		modifiers;
     int		bit;
     int		key;
+    int		endchar = (flags & FSK_CURLY) ? '}' : '>';
     uvarnumber_T	n;
     int		l;
 
     src = *srcp;
-    if (src[0] != '<')
+    if (src[0] != ((flags & FSK_CURLY) ? '{' : '<'))
 	return 0;
 
     // Find end of modifier list
@@ -2800,15 +2796,15 @@
 		// Anything accepted, like <C-?>.
 		// <C-"> or <M-"> are not special in strings as " is
 		// the string delimiter. With a backslash it works: <M-\">
-		if (!(in_string && bp[1] == '"') && bp[l + 1] == '>')
+		if (!(in_string && bp[1] == '"') && bp[l + 1] == endchar)
 		    bp += l;
 		else if (in_string && bp[1] == '\\' && bp[2] == '"'
-							       && bp[3] == '>')
+							   && bp[3] == endchar)
 		    bp += 2;
 	    }
 	}
 	if (bp[0] == 't' && bp[1] == '_' && bp[2] && bp[3])
-	    bp += 3;	// skip t_xx, xx may be '-' or '>'
+	    bp += 3;	// skip t_xx, xx may be '-' or '>'/'}'
 	else if (STRNICMP(bp, "char-", 5) == 0)
 	{
 	    vim_str2nr(bp + 5, NULL, &l, STR2NR_ALL, NULL, NULL, 0, TRUE);
@@ -2822,7 +2818,7 @@
 	}
     }
 
-    if (*bp == '>')	// found matching '>'
+    if (*bp == endchar)	// found matching '>' or '}'
     {
 	end_of_name = bp + 1;
 
@@ -2868,12 +2864,12 @@
 		    l = mb_ptr2len(last_dash + off);
 		else
 		    l = 1;
-		if (modifiers != 0 && last_dash[l + off] == '>')
+		if (modifiers != 0 && last_dash[l + off] == endchar)
 		    key = PTR2CHAR(last_dash + off);
 		else
 		{
 		    key = get_special_key_code(last_dash + off);
-		    if (!keep_x_key)
+		    if (!(flags & FSK_KEEP_X_KEY))
 			key = handle_x_keys(key);
 		}
 	    }
@@ -2890,7 +2886,7 @@
 		 */
 		key = simplify_key(key, &modifiers);
 
-		if (!keycode)
+		if (!(flags & FSK_KEYCODE))
 		{
 		    // don't want keycode, use single byte code
 		    if (key == K_BS)
@@ -2902,7 +2898,7 @@
 		// Normal Key with modifier: Try to make a single byte code.
 		if (!IS_SPECIAL(key))
 		    key = extract_modifiers(key, &modifiers,
-						       simplify, did_simplify);
+					   flags & FSK_SIMPLIFY, did_simplify);
 
 		*modp = modifiers;
 		*srcp = end_of_name;
diff --git a/src/option.c b/src/option.c
index 8574f7f..45a6231 100644
--- a/src/option.c
+++ b/src/option.c
@@ -4330,7 +4330,8 @@
     {
 	--arg;			    // put arg at the '<'
 	modifiers = 0;
-	key = find_special_key(&arg, &modifiers, TRUE, TRUE, FALSE, TRUE, NULL);
+	key = find_special_key(&arg, &modifiers,
+			    FSK_KEYCODE | FSK_KEEP_X_KEY | FSK_SIMPLIFY, NULL);
 	if (modifiers)		    // can't handle modifiers here
 	    key = 0;
     }
diff --git a/src/proto/misc2.pro b/src/proto/misc2.pro
index 592c7d1..44f22f2 100644
--- a/src/proto/misc2.pro
+++ b/src/proto/misc2.pro
@@ -68,9 +68,9 @@
 int simplify_key(int key, int *modifiers);
 int handle_x_keys(int key);
 char_u *get_special_key_name(int c, int modifiers);
-int trans_special(char_u **srcp, char_u *dst, int keycode, int in_string, int simplify, int *did_simplify);
+int trans_special(char_u **srcp, char_u *dst, int flags, int *did_simplify);
 int special_to_buf(int key, int modifiers, int keycode, char_u *dst);
-int find_special_key(char_u **srcp, int *modp, int keycode, int keep_x_key, int in_string, int simplify, int *did_simplify);
+int find_special_key(char_u **srcp, int *modp, int flags, int *did_simplify);
 int extract_modifiers(int key, int *modp, int simplify, int *did_simplify);
 int find_special_key_in_table(int c);
 int get_special_key_code(char_u *name);
diff --git a/src/term.c b/src/term.c
index 7c92f3e..f93fde8 100644
--- a/src/term.c
+++ b/src/term.c
@@ -5488,8 +5488,9 @@
 	    }
 #endif
 
-	    slen = trans_special(&src, result + dlen, TRUE, FALSE,
-			     (flags & REPTERM_NO_SIMPLIFY) == 0, did_simplify);
+	    slen = trans_special(&src, result + dlen, FSK_KEYCODE
+			  | ((flags & REPTERM_NO_SIMPLIFY) ? 0 : FSK_SIMPLIFY),
+								 did_simplify);
 	    if (slen)
 	    {
 		dlen += slen;
diff --git a/src/testdir/test_backspace_opt.vim b/src/testdir/test_backspace_opt.vim
index ad051cc..503643a 100644
--- a/src/testdir/test_backspace_opt.vim
+++ b/src/testdir/test_backspace_opt.vim
@@ -86,7 +86,7 @@
 
   set cpo-=<
   inoremap <c-u> <left><c-u>
-  exe "normal Avim3\<C-U>\<Esc>\<CR>"
+  exe "normal Avim3\{C-U}\<Esc>\<CR>"
   iunmap <c-u>
   exe "normal Avim4\<C-U>\<C-U>\<Esc>\<CR>"
 
@@ -96,7 +96,7 @@
   exe "normal A vim6\<Esc>Azwei\<C-G>u\<C-U>\<Esc>\<CR>"
 
   inoremap <c-u> <left><c-u>
-  exe "normal A vim7\<C-U>\<C-U>\<Esc>\<CR>"
+  exe "normal A vim7\{C-U}\{C-U}\<Esc>\<CR>"
 
   call assert_equal([
         \ "1 this shouldn't be deleted",
diff --git a/src/testdir/test_mapping.vim b/src/testdir/test_mapping.vim
index f6e7124..7eb6e34 100644
--- a/src/testdir/test_mapping.vim
+++ b/src/testdir/test_mapping.vim
@@ -76,7 +76,7 @@
   inoremap <c-c> <ctrl-c>
   cnoremap <c-c> dummy
   cunmap <c-c>
-  call feedkeys("GoTEST2: CTRL-C |\<C-C>A|\<Esc>", "xt")
+  call feedkeys("GoTEST2: CTRL-C |\{C-C}A|\<Esc>", "xt")
   call assert_equal('TEST2: CTRL-C |<ctrl-c>A|', getline('$'))
   unmap! <c-c>
   set nomodified
@@ -85,7 +85,7 @@
 func Test_map_ctrl_c_visual()
   " mapping of ctrl-c in Visual mode
   vnoremap <c-c> :<C-u>$put ='vmap works'
-  call feedkeys("GV\<C-C>\<CR>", "xt")
+  call feedkeys("GV\{C-C}\<CR>", "xt")
   call assert_equal('vmap works', getline('$'))
   vunmap <c-c>
   set nomodified
@@ -235,7 +235,7 @@
 
 func Test_map_meta_quotes()
   imap <M-"> foo
-  call feedkeys("Go-\<M-\">-\<Esc>", "xt")
+  call feedkeys("Go-\{M-\"}-\<Esc>", "xt")
   call assert_equal("-foo-", getline('$'))
   set nomodified
   iunmap <M-">
diff --git a/src/testdir/test_messages.vim b/src/testdir/test_messages.vim
index b74ad2c..832762a 100644
--- a/src/testdir/test_messages.vim
+++ b/src/testdir/test_messages.vim
@@ -309,7 +309,7 @@
 func Test_mapping_at_hit_return_prompt()
   nnoremap <C-B> :echo "hit ctrl-b"<CR>
   call feedkeys(":ls\<CR>", "xt")
-  call feedkeys("\<C-B>", "xt")
+  call feedkeys("\{C-B}", "xt")
   call assert_match('hit ctrl-b', Screenline(&lines - 1))
   nunmap <C-B>
 endfunc
diff --git a/src/typval.c b/src/typval.c
index cd2a862..95b2792 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -1285,15 +1285,24 @@
 			  ++name;
 			  break;
 
-			    // Special key, e.g.: "\<C-W>"
-		case '<': extra = trans_special(&p, name, TRUE, TRUE,
-								   TRUE, NULL);
-			  if (extra != 0)
+			  // Special key, e.g.: "\<C-W>" or "\{C-W}"
+		case '<':
+		case '{':
 			  {
-			      name += extra;
-			      if (name >= rettv->vval.v_string + len)
-				  iemsg("get_string_tv() used more space than allocated");
-			      break;
+			      int flags = FSK_KEYCODE | FSK_IN_STRING;
+
+			      if (*p == '<')
+				  flags |= FSK_SIMPLIFY;
+			      else
+				  flags |= FSK_CURLY;
+			      extra = trans_special(&p, name, flags, NULL);
+			      if (extra != 0)
+			      {
+				  name += extra;
+				  if (name >= rettv->vval.v_string + len)
+				      iemsg("get_string_tv() used more space than allocated");
+				  break;
+			      }
 			  }
 			  // FALLTHROUGH
 
diff --git a/src/version.c b/src/version.c
index 6fe96a3..b3aa840 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    855,
+/**/
     854,
 /**/
     853,
diff --git a/src/vim.h b/src/vim.h
index 68cf943..4fc982a 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2661,4 +2661,11 @@
 #define EVAL_EVALUATE	    1	    // when missing don't actually evaluate
 #define EVAL_CONSTANT	    2	    // when not a constant return FAIL
 
+// Flags for find_special_key()
+#define FSK_KEYCODE	0x01	// prefer key code, e.g. K_DEL instead of DEL
+#define FSK_KEEP_X_KEY	0x02	// don't translate xHome to Home key
+#define FSK_IN_STRING	0x04	// TRUE in string, double quote is escaped
+#define FSK_SIMPLIFY	0x08	// simplify <C-H> and <A-x>
+#define FSK_CURLY	0x10	// {C-x} instead of <C-x>
+
 #endif // VIM__H