patch 8.2.0306: Vim9: :substitute(pat(repl does not work in Vim9 script

Problem:    Vim9: :substitute(pat(repl does not work in Vim9 script.
Solution:   Remember starting with a colon. (closes #5676)

src/ex_docmd.c

@@ -1647,6 +1647,9 @@ do_one_cmd(
     int		save_reg_executing = reg_executing;
     int		ni;			// set when Not Implemented
     char_u	*cmd;
+#ifdef FEAT_EVAL
+    int		starts_with_colon;
+#endif
 
     vim_memset(&ea, 0, sizeof(ea));
     ea.line1 = 1;
@@ -1689,6 +1692,7 @@ do_one_cmd(
     ea.cookie = cookie;
 #ifdef FEAT_EVAL
     ea.cstack = cstack;
+    starts_with_colon = *skipwhite(ea.cmd) == ':';
 #endif
     if (parse_command_modifiers(&ea, &errormsg, FALSE) == FAIL)
 	goto doend;
@@ -1713,7 +1717,7 @@ do_one_cmd(
 	ea.cmd = skipwhite(ea.cmd + 1);
 
 #ifdef FEAT_EVAL
-    if (current_sctx.sc_version == SCRIPT_VERSION_VIM9)
+    if (current_sctx.sc_version == SCRIPT_VERSION_VIM9 && !starts_with_colon)
 	p = find_ex_command(&ea, NULL, lookup_scriptvar, NULL);
     else
 #endif

src/testdir/test_vim9_script.vim

@@ -580,6 +580,21 @@ def Test_substitute_cmd()
   setline(1, 'something')
   :substitute(some(other(
   assert_equal('otherthing', getline(1))
+  bwipe!
+
+  " also when the context is Vim9 script
+  let lines =<< trim END
+    vim9script
+    new
+    setline(1, 'something')
+    :substitute(some(other(
+    assert_equal('otherthing', getline(1))
+    bwipe!
+  END
+  writefile(lines, 'Xvim9lines')
+  source Xvim9lines
+
+  delete('Xvim9lines')
 enddef
 
 

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    306,
 /**/
     305,
 /**/