patch 8.2.2693: Vim9: locked script variable can be changed

Problem:    Vim9: locked script variable can be changed.
Solution:   Check legacy script variable for being locked. (issue #8031)
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index c062052..867afaf 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -1355,7 +1355,17 @@
     enddef
     SetLocked()
   END
-  CheckScriptFailure(lines, 'E741: Value is locked: name')
+  CheckScriptFailure(lines, 'E741: Value is locked: name', 1)
+
+  lines =<< trim END
+    let s:legacy = 'one'
+    lockvar s:legacy
+    def SetLocked()
+      s:legacy = 'two'
+    enddef
+    call SetLocked()
+  END
+  CheckScriptFailure(lines, 'E741: Value is locked: s:legacy', 1)
 
   lines =<< trim END
     vim9script
@@ -1365,7 +1375,7 @@
     SetGlobalConst()
     g:globConst = 234
   END
-  CheckScriptFailure(lines, 'E741: Value is locked: globConst')
+  CheckScriptFailure(lines, 'E741: Value is locked: globConst', 1)
   unlet g:globConst
 
   lines =<< trim END
diff --git a/src/version.c b/src/version.c
index 1059585..760a0f4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2693,
+/**/
     2692,
 /**/
     2691,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 69254be..81041bb 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -1942,6 +1942,9 @@
 			store_var(name, STACK_TV_BOT(0));
 		    else
 		    {
+			SOURCING_LNUM = iptr->isn_lnum;
+			if (var_check_permission(di, name) == FAIL)
+			    goto on_error;
 			clear_tv(&di->di_tv);
 			di->di_tv = *STACK_TV_BOT(0);
 		    }