Fixed up a few comments.

src/bootstrap/lib.rs

@@ -197,11 +197,11 @@ pub struct Compiler {
 
 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
 pub enum DocTests {
- // Default, run normal tests and doc tests.
+ /// Run normal tests and doc tests (default).
  Yes,
- // Do not run any doc tests.
+ /// Do not run any doc tests.
  No,
- // Only run doc tests.
+ /// Only run doc tests.
  Only,
 }
 
@@ -221,10 +221,10 @@ pub enum GitRepo {
 /// methods specifically on this structure itself (to make it easier to
 /// organize).
 pub struct Build {
- // User-specified configuration via config.toml
+ /// User-specified configuration from `config.toml`.
  config: Config,
 
- // Derived properties from the above two configurations
+ // Properties derived from the above configuration
  src: PathBuf,
  out: PathBuf,
  rust_info: channel::GitInfo,
@@ -240,12 +240,12 @@ pub struct Build {
  doc_tests: DocTests,
  verbosity: usize,
 
- // Targets for which to build.
+ // Targets for which to build
  build: Interned<String>,
  hosts: Vec<Interned<String>>,
  targets: Vec<Interned<String>>,
 
- // Stage 0 (downloaded) compiler and cargo or their local rust equivalents.
+ // Stage 0 (downloaded) compiler and cargo or their local rust equivalents
  initial_rustc: PathBuf,
  initial_cargo: PathBuf,
 
@@ -255,7 +255,7 @@ pub struct Build {
  cxx: HashMap<Interned<String>, cc::Tool>,
  ar: HashMap<Interned<String>, PathBuf>,
  ranlib: HashMap<Interned<String>, PathBuf>,
- // Misc
+ // Miscellaneous
  crates: HashMap<Interned<String>, Crate>,
  is_sudo: bool,
  ci_env: CiEnv,

src/librustc_typeck/check/mod.rs

@@ -4458,7 +4458,7 @@ pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, t
  return;
  }
 
- // Make a vector of booleans initially false, set to true when used.
+ // Make a vector of booleans initially `false`; set to `true` when used.
  let mut types_used = vec![false; own_counts.types];
 
  for leaf_ty in ty.walk() {
@@ -4467,7 +4467,7 @@ pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, t
  types_used[index as usize - own_counts.lifetimes] = true;
  } else if let ty::Error = leaf_ty.sty {
  // If there is already another error, do not emit
- // an error for not using a type Parameter.
+ // an error for not using a type parameter.
  assert!(tcx.sess.has_errors());
  return;
  }