From 0b642e7ae0fae6c2a2f60e241e2e79677e71dc93 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Mon, 10 Feb 2020 22:41:45 -0500
Subject: [PATCH] precompile: avoid a potential crash when adding methods

fixes #29859
---
 src/gf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/gf.c b/src/gf.c
index 97d4d50afd6b1..16aaf85bb4fae 100644
--- a/src/gf.c
+++ b/src/gf.c
@@ -1356,7 +1356,8 @@ static int check_ambiguous_visitor(jl_typemap_entry_t *oldentry, struct typemap_
 
     // ok: record that this method definition is being partially replaced
     // (either with a real definition, or an ambiguity error)
-    if (shadowed) {
+    // be careful not to try to scan something from the current dump-reload though
+    if (shadowed && oldentry->min_world != closure->newentry->min_world) {
         if (closure->shadowed == NULL) {
             closure->shadowed = (jl_value_t*)oldentry;
         }