patch 8.2.3475: expression register set by not executed put command Commit: https://github.com/vim/vim/commit/08d7b1c82866a61b61a55e55b6c190dba04e54ea Author: kuuote <znmxodq1@gmail.com> Date: Mon Oct 4 22:17:36 2021 +0100 patch 8.2.3475: expression register set by not executed put command Problem: Expression register set by not executed put command. Solution: Do not set the register if the command is skipped. (closes https://github.com/vim/vim/issues/8909)

--- a/src/testdir/test_excmd.vim
+++ b/src/testdir/test_excmd.vim
@@ -647,4 +647,12 @@ func Test_command_not_implemented_E319()
   endif
 endfunc
 
+func Test_not_break_expression_register()
+  call setreg('=', '1+1')
+  if 0
+    put =1
+  endif
+  call assert_equal('1+1', getreg('=', 1))
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab