Fix some comment formatting.

compiler/rustc_expand/src/config.rs

@@ -99,10 +99,11 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
             // If the declared feature is unstable, record it.
             if let Some(f) = UNSTABLE_FEATURES.iter().find(|f| name == f.feature.name) {
                 (f.set_enabled)(&mut features);
-                // When the ICE comes from core, alloc or std (approximation of the standard library), there's a chance
+                // When the ICE comes from core, alloc or std (approximation of the standard
-                // that the person hitting the ICE may be using -Zbuild-std or similar with an untested target.
+                // library), there's a chance that the person hitting the ICE may be using
-                // The bug is probably in the standard library and not the compiler in that case, but that doesn't
+                // -Zbuild-std or similar with an untested target. The bug is probably in the
-                // really matter - we want a bug report.
+                // standard library and not the compiler in that case, but that doesn't really
+                // matter - we want a bug report.
                 if features.internal(name)
                     && ![sym::core, sym::alloc, sym::std].contains(&crate_name)
                 {

compiler/rustc_expand/src/expand.rs

@@ -505,8 +505,9 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
 
                     let (fragment, collected_invocations) =
                         self.collect_invocations(fragment, &derive_placeholders);
-                    // We choose to expand any derive invocations associated with this macro invocation
+                    // We choose to expand any derive invocations associated with this macro
-                    // *before* any macro invocations collected from the output fragment
+                    // invocation *before* any macro invocations collected from the output
+                    // fragment.
                     derive_invocations.extend(collected_invocations);
                     (fragment, derive_invocations)
                 }

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -28,7 +28,8 @@ pub(super) fn failed_to_match_macro<'cx>(
 ) -> Box<dyn MacResult + 'cx> {
     let psess = &cx.sess.psess;
 
-    // An error occurred, try the expansion again, tracking the expansion closely for better diagnostics.
+    // An error occurred, try the expansion again, tracking the expansion closely for better
+    // diagnostics.
     let mut tracker = CollectTrackerAndEmitter::new(cx, sp);
 
     let try_success_result = try_match_macro(psess, name, &arg, lhses, &mut tracker);

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -157,8 +157,8 @@ pub(super) trait Tracker<'matcher> {
     /// This is called before trying to match next MatcherLoc on the current token.
     fn before_match_loc(&mut self, _parser: &TtParser, _matcher: &'matcher MatcherLoc) {}
 
-    /// This is called after an arm has been parsed, either successfully or unsuccessfully. When this is called,
+    /// This is called after an arm has been parsed, either successfully or unsuccessfully. When
-    /// `before_match_loc` was called at least once (with a `MatcherLoc::Eof`).
+    /// this is called, `before_match_loc` was called at least once (with a `MatcherLoc::Eof`).
     fn after_arm(&mut self, _result: &NamedParseResult<Self::Failure>) {}
 
     /// For tracing.
@@ -169,7 +169,8 @@ pub(super) trait Tracker<'matcher> {
     }
 }
 
-/// A noop tracker that is used in the hot path of the expansion, has zero overhead thanks to monomorphization.
+/// A noop tracker that is used in the hot path of the expansion, has zero overhead thanks to
+/// monomorphization.
 pub(super) struct NoopTracker;
 
 impl<'matcher> Tracker<'matcher> for NoopTracker {
@@ -492,7 +493,7 @@ pub fn compile_declarative_macro(
                     .pop()
                     .unwrap();
                     // We don't handle errors here, the driver will abort
-                    // after parsing/expansion. we can report every error in every macro this way.
+                    // after parsing/expansion. We can report every error in every macro this way.
                     check_emission(check_lhs_nt_follows(sess, def, &tt));
                     return tt;
                 }
@@ -528,7 +529,7 @@ pub fn compile_declarative_macro(
         check_emission(check_rhs(sess, rhs));
     }
 
-    // don't abort iteration early, so that errors for multiple lhses can be reported
+    // Don't abort iteration early, so that errors for multiple lhses can be reported.
     for lhs in &lhses {
         check_emission(check_lhs_no_empty_seq(sess, slice::from_ref(lhs)));
     }