fix a couple links

Author: mark-i-m

src/pat-exhaustive-checking.md

@@ -80,9 +80,9 @@ fn foo(Foo { x, y }: Foo) {
 
 ## The algorithm
 
-Exhaustiveness checking is implemented in [check_match].
-The core of the algorithm is in [_match].
+Exhaustiveness checking is implemented in [`check_match`].
+The core of the algorithm is in [`usefulness`].
 That file contains a detailed description of the algorithm.
 
-[check_match]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir_build/thir/pattern/check_match/index.html
-[_match]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir_build/thir/pattern/_match/index.html
+[`check_match`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir_build/thir/pattern/check_match/index.html
+[`usefulness`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir_build/thir/pattern/usefulness/index.html

src/traits/hrtb.md

@@ -42,7 +42,7 @@ subtyping, we recommend you read the paper). There are a few parts:
 
 [hrsubtype]: ./hrtb.md
 [placeholder]: ../appendix/glossary.html#placeholder
-[paper by SPJ]: http://research.microsoft.com/en-us/um/people/simonpj/papers/higher-rank/
+[paper by SPJ]: https://www.microsoft.com/en-us/research/publication/practical-type-inference-for-arbitrary-rank-types
 
 So let's work through our example.