commit https://github.com/vim/vim/commit/f5a39447a8ebe162ee62caa2ee502cd0e65eecaa Author: Bram Moolenaar <Bram@vim.org> Date: Tue Aug 16 21:04:41 2016 +0200 patch 7.4.2219 Problem: Recursive call to substitute gets stuck in sandbox. (Nikolai Pavlov) Solution: Handle the recursive call. (Christian Brabandt, closes https://github.com/vim/vim/issues/950) Add a test.

--- a/src/testdir/test_regexp_latin.vim
+++ b/src/testdir/test_regexp_latin.vim
@@ -30,3 +30,12 @@ func Test_equivalence_re2()
   set re=2
   call s:equivalence_test()
 endfunc
+
+func Test_recursive_substitute()
+  new
+  s/^/\=execute("s#^##gn")
+  " check we are now not in the sandbox
+  call setwinvar(1, 'myvar', 1)
+  bwipe!
+endfunc
+