Merge pull request #30380 from zeertzjq/backport

Manual backport of #30377 to release-0.10

src/nvim/quickfix.c

@@ -6936,6 +6936,11 @@ bool set_ref_in_quickfix(int copyID)
       if (abort) {
         return abort;
       }
+
+      abort = mark_quickfix_user_data(win->w_llist_ref, copyID);
+      if (abort) {
+        return abort;
+      }
     }
   }
 

test/old/testdir/test_quickfix.vim

@@ -4072,11 +4072,23 @@ func Test_ll_window_ctx()
   enew | only
 endfunc
 
+" Similar to the problem above, but for user data.
+func Test_ll_window_user_data()
+  call setloclist(0, [#{bufnr: bufnr(), user_data: {}}])
+  lopen
+  wincmd t
+  close
+  call test_garbagecollect_now()
+  call feedkeys("\<CR>", 'tx')
+  call test_garbagecollect_now()
+  %bwipe!
+endfunc
+
 " The following test used to crash vim
 func Test_lfile_crash()
   sp Xtest
   au QuickFixCmdPre * bw
-  call assert_fails('lfile', 'E40')
+  call assert_fails('lfile', 'E40:')
   au! QuickFixCmdPre
 endfunc