Edit the "Compiler Source Code" chapter

src/compiler-src.md

@@ -3,7 +3,10 @@
 <!-- toc -->
 
 Now that we have [seen what the compiler does](./overview.md), let's take a
-look at the structure of the contents of the rust-lang/rust repo.
+look at the structure of the [`rust-lang/rust`] repository, where the rustc
+source code lives.
+
+[`rust-lang/rust`]: https://github.com/rust-lang/rust
 
 ## Workspace structure
 
@@ -16,22 +19,11 @@ The repository consists of three main directories:
 
 - `compiler/` contains the source code for `rustc`. It consists of many crates
   that together make up the compiler.
-
 - `library/` contains the standard libraries (`core`, `alloc`, `std`,
   `proc_macro`, `test`), as well as the Rust runtime (`backtrace`, `rtstartup`,
   `lang_start`).
-
 - `src/` contains the source code for rustdoc, clippy, cargo, the build system,
-  language docs, etc.
-
-## Standard library
-
-The standard library crates are all in `library/`. They have intuitive names
-like `std`, `core`, `alloc`, etc.  There is also `proc_macro`, `test`, and
-other runtime libraries.
-
-This code is fairly similar to most other Rust crates except that it must be
-built in a special way because it can use unstable features.
+  compiler tests, language docs, etc.
 
 ## Compiler
 
@@ -87,7 +79,7 @@ explanation of these crates here.
 
 ### Big picture
 
-The dependency structure is influenced strongly by two main factors:
+The dependency structure is influenced by two main factors:
 
 1. Organization. The compiler is a _huge_ codebase; it would be an impossibly
    large crate. In part, the dependency structure reflects the code structure
@@ -101,12 +93,9 @@ At the very bottom of the dependency tree are a handful of crates that are used
 by the whole compiler (e.g. [`rustc_span`]). The very early parts of the
 compilation process (e.g. parsing and the AST) depend on only these.
 
-Pretty soon after the AST is constructed, the compiler's [query system][query]
-gets set up.  The query system is set up in a clever way using function
-pointers. This allows us to break dependencies between crates, allowing more
-parallel compilation.
-
-However, since the query system is defined in [`rustc_middle`], nearly all
+After the AST is constructed, the compiler's [query system][query]
+gets set up.[^query-setup]
+The query system is defined in [`rustc_middle`], so nearly all
 subsequent parts of the compiler depend on this crate. It is a really large
 crate, leading to long compile times. Some efforts have been made to move stuff
 out of it with limited success. Another unfortunate side effect is that sometimes
@@ -116,7 +105,7 @@ linting functionality is scattered across earlier parts of the crate,
 
 [`rustc_lint`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/index.html
 
-More generally, in an ideal world, it seems like there would be fewer, more
+Ideally there would be fewer, more
 cohesive crates, with incremental and parallel compilation making sure compile
 times stay reasonable. However, our incremental and parallel compilation haven't
 gotten good enough for that yet, so breaking things into separate crates has
@@ -134,6 +123,10 @@ compilation to completion.
 
 [orgch]: ./overview.md
 
+[^query-setup]: The query system is set up in a clever way using function
+pointers. This allows us to break dependencies between crates, allowing more
+parallel compilation.
+
 ## rustdoc
 
 The bulk of `rustdoc` is in [`librustdoc`]. However, the `rustdoc` binary