Added links back to nrc's stupid-stats

Author: Michael-F-Bryan

src/appendix-stupid-stats.md

@@ -1,5 +1,10 @@
 # Appendix A: A tutorial on creating a drop-in replacement for rustc
 
+> **Note:** This is a copy of `@nrc`'s amazing [stupid-stats]. You should find
+> a copy of the code on the GitHub repository although due to the compiler's
+> constantly evolving nature, there is no guarantee it'll compile on the first
+> go. 
+
 Many tools benefit from being a drop-in replacement for a compiler. By this, I
 mean that any user of the tool can use `mytool` in all the ways they would
 normally use `rustc` - whether manually compiling a single file or as part of a
@@ -395,4 +400,6 @@ It'd be great to see Rustdoc converted to using these APIs, if that is possible
 analysis, rather than doing its own analysis). Other parts of the compiler
 (e.g., pretty printing, testing) could be refactored to use these APIs
 internally (I already changed save-analysis to use `CompilerController`). I've
-been experimenting with a prototype rustfmt which also uses these APIs.
+been experimenting with a prototype rustfmt which also uses these APIs.
+
+[stupid-stats]: https://github.com/nrc/stupid-stats

src/rustc-driver.md

@@ -39,6 +39,9 @@ compilation process
 The `CompileState`'s various `state_after_*()` constructors can be inspected to
 determine what bits of information are available to which callback.
 
+For a more detailed explanation on using `rustc_driver`, check out the 
+[stupid-stats] guide by `@nrc` (attached as [Appendix A]).
+
 > **Warning:** By its very nature, the internal compiler APIs are always going
 > to be unstable. That said, we do try not to break things unnecessarily.
 
@@ -68,4 +71,6 @@ thread-locals, although you should rarely need to touch it.
 [`CompileState`]: https://github.com/rust-lang/rust/blob/master/src/librustc_driver/driver.rs
 [`Session`]: https://github.com/rust-lang/rust/blob/master/src/librustc/session/mod.rs
 [`TyCtxt`]: https://github.com/rust-lang/rust/blob/master/src/librustc/ty/context.rs
-[`CodeMap`]: https://github.com/rust-lang/rust/blob/master/src/libsyntax/codemap.rs
+[`CodeMap`]: https://github.com/rust-lang/rust/blob/master/src/libsyntax/codemap.rs
+[stupid-stats]: https://github.com/nrc/stupid-stats
+[Appendix A]: appendix-stupid-stats.html