error[E0609]: no field `zz` on type `Foo`
  --> $DIR/issue-36798_unknown_field.rs:17:7
   |
LL |     f.zz; //~ ERROR no field
   |       ^^ unknown field
   |
   = note: available fields are: `bar`

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0609"