9ace0de26b
Prefer to use repeat_n over repeat().take()
More from https://github.com/rust-lang/rust/pull/147464, but batch processed with `ast-grep` to find and replace.
second commit add notes for library: affaf532f9
r? ``@RalfJung``
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.