patch 8.2.1352: Vim9: no error for shadowing a script-local function

Problem:    Vim9: no error for shadowing a script-local function by a nested
            function.
Solution:   Check for script-local function. (closes #6586)

src/testdir/test_vim9_func.vim

@@ -174,6 +174,20 @@ def Test_nested_global_function()
       Outer()
   END
   CheckScriptFailure(lines, "E122:")
+
+  lines =<< trim END
+      vim9script
+      def Func()
+        echo 'script'
+      enddef
+      def Outer()
+        def Func()
+          echo 'inner'
+        enddef
+      enddef
+      defcompile
+  END
+  CheckScriptFailure(lines, "E1073:")
 enddef
 
 def Test_global_local_function()

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1352,
 /**/
     1351,
 /**/

src/vim9compile.c

@@ -291,15 +291,21 @@ lookup_script(char_u *name, size_t len)
     int
 check_defined(char_u *p, size_t len, cctx_T *cctx)
 {
+    int c = p[len];
+
+    p[len] = NUL;
     if (lookup_script(p, len) == OK
 	    || (cctx != NULL
 		&& (lookup_local(p, len, cctx) != NULL
 		    || lookup_arg(p, len, NULL, NULL, NULL, cctx) == OK))
-	    || find_imported(p, len, cctx) != NULL)
+	    || find_imported(p, len, cctx) != NULL
+	    || find_func_even_dead(p, FALSE, cctx) != NULL)
     {
+	p[len] = c;
 	semsg(_(e_already_defined), p);
 	return FAIL;
     }
+    p[len] = c;
     return OK;
 }