Rollup merge of #80803 - jyn514:cleanup-fill-in, r=GuillaumeGomez
Rollup merge of #80803 - jyn514:cleanup-fill-in, r=GuillaumeGomez

Remove useless `fill_in` function

It was only used once, in a function that was otherwise trivial.

aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust