attr/passes: comment -> doc comment

Change some regular comments into documentation comments.

Signed-off-by: David Wood <david.wood@huawei.com>

Author: davidtwco

compiler/rustc_attr/src/builtin.rs

@@ -135,9 +135,22 @@ impl ConstStability {
 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 #[derive(HashStable_Generic)]
 pub enum StabilityLevel {
-    // Reason for the current stability level and the relevant rust-lang issue
-    Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
-    Stable { since: Symbol, allowed_through_unstable_modules: bool },
+    /// `#[unstable]`
+    Unstable {
+        /// Reason for the current stability level.
+        reason: Option<Symbol>,
+        /// Relevant `rust-lang/rust` issue.
+        issue: Option<NonZeroU32>,
+        is_soft: bool,
+    },
+    /// `#[stable]`
+    Stable {
+        /// Rust release which stabilized this feature.
+        since: Symbol,
+        /// Is this item allowed to be referred to on stable, despite being contained in unstable
+        /// modules?
+        allowed_through_unstable_modules: bool,
+    },
 }
 
 impl StabilityLevel {

compiler/rustc_passes/src/lib_features.rs

@@ -1,8 +1,8 @@
-// Detecting lib features (i.e., features that are not lang features).
-//
-// These are declared using stability attributes (e.g., `#[stable (..)]`
-// and `#[unstable (..)]`), but are not declared in one single location
-// (unlike lang features), which means we need to collect them instead.
+//! Detecting lib features (i.e., features that are not lang features).
+//!
+//! These are declared using stability attributes (e.g., `#[stable (..)]` and `#[unstable (..)]`),
+//! but are not declared in one single location (unlike lang features), which means we need to
+//! collect them instead.
 
 use rustc_ast::{Attribute, MetaItemKind};
 use rustc_errors::struct_span_err;

compiler/rustc_passes/src/stability.rs

@@ -29,13 +29,13 @@ use std::num::NonZeroU32;
 
 #[derive(PartialEq)]
 enum AnnotationKind {
-    // Annotation is required if not inherited from unstable parents
+    /// Annotation is required if not inherited from unstable parents.
     Required,
-    // Annotation is useless, reject it
+    /// Annotation is useless, reject it.
     Prohibited,
-    // Deprecation annotation is useless, reject it. (Stability attribute is still required.)
+    /// Deprecation annotation is useless, reject it. (Stability attribute is still required.)
     DeprecationProhibited,
-    // Annotation itself is useless, but it can be propagated to children
+    /// Annotation itself is useless, but it can be propagated to children.
     Container,
 }
 
@@ -83,7 +83,7 @@ impl InheritStability {
     }
 }
 
-// A private tree-walker for producing an Index.
+/// A private tree-walker for producing an `Index`.
 struct Annotator<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     index: &'a mut Index,
@@ -94,9 +94,9 @@ struct Annotator<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Annotator<'a, 'tcx> {
-    // Determine the stability for a node based on its attributes and inherited
-    // stability. The stability is recorded in the index and used as the parent.
-    // If the node is a function, `fn_sig` is its signature
+    /// Determine the stability for a node based on its attributes and inherited stability. The
+    /// stability is recorded in the index and used as the parent. If the node is a function,
+    /// `fn_sig` is its signature.
     fn annotate<F>(
         &mut self,
         def_id: LocalDefId,