Using the same key to select completion and expand snippet

Hello, I have been trying to configure asyncomplete so that in the pop up menu `<CR>` will expand a snippet if one is selected, otherwise insert the completion. My best attempt has been
```
imap <expr><CR> pumvisible() ? neosnippet#expandable() ? "\<Plug>(neosnippet_expand)" : "<C-y>" : "\<CR>"
```
but this seems to always choose a snippet if one is listed.