From c7f7f6db3e9d3b6b723ed17d5244c83859583832 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Wed, 4 Nov 2020 13:38:28 +0100
Subject: [PATCH] patch 8.2.1952: Vim9: crash when using a NULL dict key

Problem:    Vim9: crash when using a NULL dict key.
Solution:   Use a NULL dict key like an empty string. (closes #7249)
---
 src/testdir/test_vim9_expr.vim | 2 ++
 src/version.c                  | 2 ++
 src/vim9execute.c              | 9 ++++++---
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 656718c49..2d741e495 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -1902,6 +1902,8 @@ def Test_expr7_dict()
   var dictdict: dict<dict<string>> = #{one: #{a: 'text'}, two: #{}}
   dictdict = #{one: #{}, two: #{a: 'text'}}
   dictdict = #{one: #{}, two: #{}}
+
+  assert_equal({'': 0}, {matchstr('string', 'wont match'): 0})
  
   CheckDefFailure(["var x = #{a:8}"], 'E1069:', 1)
   CheckDefFailure(["var x = #{a : 8}"], 'E1068:', 1)
diff --git a/src/version.c b/src/version.c
index d677744ee..98a3ab153 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1952,
 /**/
     1951,
 /**/
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 33027871a..eb0e1db63 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -1738,6 +1738,7 @@ call_def_function(
 		    int		count = iptr->isn_arg.number;
 		    dict_T	*dict = dict_alloc();
 		    dictitem_T	*item;
+		    char_u	*key;
 
 		    if (dict == NULL)
 			goto failed;
@@ -1746,15 +1747,17 @@ call_def_function(
 			// have already checked key type is VAR_STRING
 			tv = STACK_TV_BOT(2 * (idx - count));
 			// check key is unique
-			item = dict_find(dict, tv->vval.v_string, -1);
+			key = tv->vval.v_string == NULL
+					    ? (char_u *)"" : tv->vval.v_string;
+			item = dict_find(dict, key, -1);
 			if (item != NULL)
 			{
 			    SOURCING_LNUM = iptr->isn_lnum;
-			    semsg(_(e_duplicate_key), tv->vval.v_string);
+			    semsg(_(e_duplicate_key), key);
 			    dict_unref(dict);
 			    goto on_error;
 			}
-			item = dictitem_alloc(tv->vval.v_string);
+			item = dictitem_alloc(key);
 			clear_tv(tv);
 			if (item == NULL)
 			{
-- 
2.40.0