From cfe3af284a26178f4838df7c7489b2a1edd4c3a1 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Thu, 30 Dec 2021 13:59:20 +0000
Subject: [PATCH] patch 8.2.3948: Vim9: failure with partial with unknown
 argument count

Problem:    Vim9: failure with partial with unknown argument count.
Solution:   Do not copy argument types if there aren't any.
---
 src/version.c  |  2 ++
 src/vim9type.c | 21 ++++++++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/src/version.c b/src/version.c
index 56825f547b565..a362dca9a7d3c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3948,
 /**/
     3947,
 /**/
diff --git a/src/vim9type.c b/src/vim9type.c
index a9fb5b0e7875c..c6e80e6777c92 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -369,19 +369,22 @@ typval2type_int(typval_T *tv, int copyID, garray_T *type_gap, int do_member)
 		    if (type == NULL)
 			return NULL;
 		    *type = *ufunc->uf_func_type;
-		    type->tt_argcount -= tv->vval.v_partial->pt_argc;
-		    type->tt_min_argcount -= tv->vval.v_partial->pt_argc;
-		    if (type->tt_argcount == 0)
-			type->tt_args = NULL;
-		    else
+		    if (type->tt_argcount >= 0)
 		    {
-			int i;
+			type->tt_argcount -= tv->vval.v_partial->pt_argc;
+			type->tt_min_argcount -= tv->vval.v_partial->pt_argc;
+			if (type->tt_argcount == 0)
+			    type->tt_args = NULL;
+			else
+			{
+			    int i;
 
-			func_type_add_arg_types(type, type->tt_argcount,
+			    func_type_add_arg_types(type, type->tt_argcount,
 								     type_gap);
-			for (i = 0; i < type->tt_argcount; ++i)
-			    type->tt_args[i] = ufunc->uf_func_type->tt_args[
+			    for (i = 0; i < type->tt_argcount; ++i)
+				type->tt_args[i] = ufunc->uf_func_type->tt_args[
 					      i + tv->vval.v_partial->pt_argc];
+			}
 		    }
 		    return type;
 		}