Fixed up a few comments.

Author: Alexander Regueiro

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;
         }