patch 8.2.2673: Vim9: script-local funcref can have lower case name

Problem:    Vim9: script-local funcref can have lower case name.
Solution:   Require an upper case name.

src/evalvars.c

@@ -3453,8 +3453,10 @@ var_wrong_func_name(
     char_u *name,    // points to start of variable name
     int    new_var)  // TRUE when creating the variable
 {
-    // Allow for w: b: s: and t:.
+    // Allow for w: b: s: and t:.  In Vim9 script s: is not allowed, because
-    if (!(vim_strchr((char_u *)"wbst", name[0]) != NULL && name[1] == ':')
+    // the name can be used without the s: prefix.
+    if (!((vim_strchr((char_u *)"wbt", name[0]) != NULL
+		    || (!in_vim9script() && name[0] == 's')) && name[1] == ':')
 	    && !ASCII_ISUPPER((name[0] != NUL && name[1] == ':')
 						     ? name[2] : name[0]))
     {

src/testdir/test_vim9_assign.vim

@@ -1654,5 +1654,31 @@ def Test_assign_command_modifier()
   CheckDefAndScriptSuccess(lines)
 enddef
 
+def Test_script_funcref_case()
+  var lines =<< trim END
+      var Len = (s: string): number => len(s) + 1
+      assert_equal(5, Len('asdf'))
+  END
+  CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
+      var len = (s: string): number => len(s) + 1
+  END
+  CheckDefAndScriptFailure(lines, 'E704:')
+
+  lines =<< trim END
+      vim9script
+      var s:Len = (s: string): number => len(s) + 2
+      assert_equal(6, Len('asdf'))
+  END
+  CheckScriptSuccess(lines)
+
+  lines =<< trim END
+      vim9script
+      var s:len = (s: string): number => len(s) + 1
+  END
+  CheckScriptFailure(lines, 'E704:')
+enddef
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2673,
 /**/
     2672,
 /**/