From 673bcb10ebe87ccf6954dd342d0143eb88cdfbcb Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Tue, 8 Mar 2022 16:52:24 +0000
Subject: patch 8.2.4528: crash when using null_function for a partial

Problem:    Crash when using null_function for a partial.
Solution:   Don't call fname_trans_sid() with NULL. (closes #9908)
---
 src/testdir/test_vim9_func.vim |  9 +++++++++
 src/userfunc.c                 | 17 +++++++++++------
 src/version.c                  |  2 ++
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index a47dbae27..131413b16 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -3337,6 +3337,15 @@ def Test_partial_double_nested()
   assert_equal(123, RefRef())
 enddef
 
+def Test_partial_null_function()
+  var lines =<< trim END
+      var d: dict<func> = {f: null_function}
+      var Ref = d.f
+      assert_equal('func', typename(Ref))
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+enddef
+
 " Using "idx" from a legacy global function does not work.
 " This caused a crash when called from legacy context.
 func Test_partial_call_fails()
diff --git a/src/userfunc.c b/src/userfunc.c
index 63bb3140a..f0abaee5f 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -5730,7 +5730,6 @@ func_has_abort(
 make_partial(dict_T *selfdict_in, typval_T *rettv)
 {
     char_u	*fname;
-    char_u	*tofree = NULL;
     ufunc_T	*fp;
     char_u	fname_buf[FLEN_FIXED + 1];
     int		error;
@@ -5742,13 +5741,19 @@ make_partial(dict_T *selfdict_in, typval_T *rettv)
     {
 	fname = rettv->v_type == VAR_FUNC ? rettv->vval.v_string
 					      : rettv->vval.v_partial->pt_name;
-	// Translate "s:func" to the stored function name.
-	fname = fname_trans_sid(fname, fname_buf, &tofree, &error);
-	fp = find_func(fname, FALSE);
-	vim_free(tofree);
+	if (fname != NULL)
+	{
+	    char_u	*tofree = NULL;
+
+	    // Translate "s:func" to the stored function name.
+	    fname = fname_trans_sid(fname, fname_buf, &tofree, &error);
+	    fp = find_func(fname, FALSE);
+	    vim_free(tofree);
+	}
     }
 
-    if (fp != NULL && (fp->uf_flags & FC_DICT))
+    if ((fp != NULL && (fp->uf_flags & FC_DICT))
+		|| (rettv->v_type == VAR_FUNC && rettv->vval.v_string == NULL))
     {
 	partial_T	*pt = ALLOC_CLEAR_ONE(partial_T);
 
diff --git a/src/version.c b/src/version.c
index 794591003..f6aaa7955 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 */
+/**/
+    4528,
 /**/
     4527,
 /**/
-- 
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