(global-set-key [remap write-file] (lambda () (interactive) 'rms))
    C-h f write-file RET

This yields in an error because help-fns--key-bindings expects
(command-remapping 'write-file) to be a symbol.

Here is a patch that abbreviates non-symbol remap targets with "??".
This is consistent with what describe-bindings displays.