error: struct update has no effect, all the fields in the struct have already been specified
  --> $DIR/needless_update.rs:19:23
   |
LL |     S { a: 1, b: 1, ..base };
   |                       ^^^^
   |
   = note: `-D clippy::needless-update` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::needless_update)]`

error: aborting due to 1 previous error