compiler/rustc_infer/src/infer/higher_ranked/README.md

   1 To learn more about how Higher-ranked trait bounds work in the _old_ trait
   2 solver, see [this chapter][oldhrtb] of the rustc-dev-guide.
   3
   4 To learn more about how they work in the _new_ trait solver, see [this
   5 chapter][newhrtb].
   6
   7 [oldhrtb]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
   8 [newhrtb]: https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference.html#placeholders-and-universes