expand unused doc comment diagnostic

Report the diagnostic on macro expansions, and add a label indicating
why the comment is unused.

src/libcore/num/mod.rs

@@ -4515,7 +4515,7 @@ macro_rules! rev {
     )*}
 }
 
-/// intra-sign conversions
+// intra-sign conversions
 try_from_upper_bounded!(u16, u8);
 try_from_upper_bounded!(u32, u16, u8);
 try_from_upper_bounded!(u64, u32, u16, u8);

src/librustc/hir/mod.rs

@@ -122,6 +122,7 @@ impl fmt::Display for HirId {
 // hack to ensure that we don't try to access the private parts of `ItemLocalId` in this module
 mod item_local_id_inner {
     use rustc_data_structures::indexed_vec::Idx;
+    newtype_index! {
         /// An `ItemLocalId` uniquely identifies something within a given "item-like",
         /// that is within a hir::Item, hir::TraitItem, or hir::ImplItem. There is no
         /// guarantee that the numerical value of a given `ItemLocalId` corresponds to
@@ -130,7 +131,6 @@ mod item_local_id_inner {
         /// integers starting at zero, so a mapping that maps all or most nodes within
         /// an "item-like" to something else can be implement by a `Vec` instead of a
         /// tree or hash map.
-    newtype_index! {
         pub struct ItemLocalId { .. }
     }
 }

src/librustc/middle/region.rs

@@ -132,25 +132,24 @@ pub enum ScopeData {
     Remainder(FirstStatementIndex)
 }
 
-/// Represents a subscope of `block` for a binding that is introduced
-/// by `block.stmts[first_statement_index]`. Such subscopes represent
-/// a suffix of the block. Note that each subscope does not include
-/// the initializer expression, if any, for the statement indexed by
-/// `first_statement_index`.
-///
-/// For example, given `{ let (a, b) = EXPR_1; let c = EXPR_2; ... }`:
-///
-/// * The subscope with `first_statement_index == 0` is scope of both
-///   `a` and `b`; it does not include EXPR_1, but does include
-///   everything after that first `let`. (If you want a scope that
-///   includes EXPR_1 as well, then do not use `Scope::Remainder`,
-///   but instead another `Scope` that encompasses the whole block,
-///   e.g., `Scope::Node`.
-///
-/// * The subscope with `first_statement_index == 1` is scope of `c`,
-///   and thus does not include EXPR_2, but covers the `...`.
-
 newtype_index! {
+    /// Represents a subscope of `block` for a binding that is introduced
+    /// by `block.stmts[first_statement_index]`. Such subscopes represent
+    /// a suffix of the block. Note that each subscope does not include
+    /// the initializer expression, if any, for the statement indexed by
+    /// `first_statement_index`.
+    ///
+    /// For example, given `{ let (a, b) = EXPR_1; let c = EXPR_2; ... }`:
+    ///
+    /// * The subscope with `first_statement_index == 0` is scope of both
+    ///   `a` and `b`; it does not include EXPR_1, but does include
+    ///   everything after that first `let`. (If you want a scope that
+    ///   includes EXPR_1 as well, then do not use `Scope::Remainder`,
+    ///   but instead another `Scope` that encompasses the whole block,
+    ///   e.g., `Scope::Node`.
+    ///
+    /// * The subscope with `first_statement_index == 1` is scope of `c`,
+    ///   and thus does not include EXPR_2, but covers the `...`.
     pub struct FirstStatementIndex { .. }
 }
 

src/librustc/ty/context.rs

@@ -1892,9 +1892,11 @@ pub mod tls {
         rayon_core::tlv::get()
     }
 
-    /// A thread local variable which stores a pointer to the current ImplicitCtxt
     #[cfg(not(parallel_compiler))]
-    thread_local!(static TLV: Cell<usize> = Cell::new(0));
+    thread_local! {
+        /// A thread local variable which stores a pointer to the current ImplicitCtxt.
+        static TLV: Cell<usize> = Cell::new(0);
+    }
 
     /// Sets TLV to `value` during the call to `f`.
     /// It is restored to its previous value after.
@@ -2011,10 +2013,11 @@ pub mod tls {
         })
     }
 
+    scoped_thread_local! {
         /// Stores a pointer to the GlobalCtxt if one is available.
-    /// This is used to access the GlobalCtxt in the deadlock handler
+        /// This is used to access the GlobalCtxt in the deadlock handler given to Rayon.
-    /// given to Rayon.
+        pub static GCX_PTR: Lock<usize>
-    scoped_thread_local!(pub static GCX_PTR: Lock<usize>);
+    }
 
     /// Creates a TyCtxt and ImplicitCtxt based on the GCX_PTR thread local.
     /// This is used in the deadlock handler.

src/librustc/ty/mod.rs

@@ -1512,42 +1512,42 @@ impl<'tcx> InstantiatedPredicates<'tcx> {
     }
 }
 
-/// "Universes" are used during type- and trait-checking in the
-/// presence of `for<..>` binders to control what sets of names are
-/// visible. Universes are arranged into a tree: the root universe
-/// contains names that are always visible. Each child then adds a new
-/// set of names that are visible, in addition to those of its parent.
-/// We say that the child universe "extends" the parent universe with
-/// new names.
-///
-/// To make this more concrete, consider this program:
-///
-/// ```
-/// struct Foo { }
-/// fn bar<T>(x: T) {
-///   let y: for<'a> fn(&'a u8, Foo) = ...;
-/// }
-/// ```
-///
-/// The struct name `Foo` is in the root universe U0. But the type
-/// parameter `T`, introduced on `bar`, is in an extended universe U1
-/// -- i.e., within `bar`, we can name both `T` and `Foo`, but outside
-/// of `bar`, we cannot name `T`. Then, within the type of `y`, the
-/// region `'a` is in a universe U2 that extends U1, because we can
-/// name it inside the fn type but not outside.
-///
-/// Universes are used to do type- and trait-checking around these
-/// "forall" binders (also called **universal quantification**). The
-/// idea is that when, in the body of `bar`, we refer to `T` as a
-/// type, we aren't referring to any type in particular, but rather a
-/// kind of "fresh" type that is distinct from all other types we have
-/// actually declared. This is called a **placeholder** type, and we
-/// use universes to talk about this. In other words, a type name in
-/// universe 0 always corresponds to some "ground" type that the user
-/// declared, but a type name in a non-zero universe is a placeholder
-/// type -- an idealized representative of "types in general" that we
-/// use for checking generic functions.
 newtype_index! {
+    /// "Universes" are used during type- and trait-checking in the
+    /// presence of `for<..>` binders to control what sets of names are
+    /// visible. Universes are arranged into a tree: the root universe
+    /// contains names that are always visible. Each child then adds a new
+    /// set of names that are visible, in addition to those of its parent.
+    /// We say that the child universe "extends" the parent universe with
+    /// new names.
+    ///
+    /// To make this more concrete, consider this program:
+    ///
+    /// ```
+    /// struct Foo { }
+    /// fn bar<T>(x: T) {
+    ///   let y: for<'a> fn(&'a u8, Foo) = ...;
+    /// }
+    /// ```
+    ///
+    /// The struct name `Foo` is in the root universe U0. But the type
+    /// parameter `T`, introduced on `bar`, is in an extended universe U1
+    /// -- i.e., within `bar`, we can name both `T` and `Foo`, but outside
+    /// of `bar`, we cannot name `T`. Then, within the type of `y`, the
+    /// region `'a` is in a universe U2 that extends U1, because we can
+    /// name it inside the fn type but not outside.
+    ///
+    /// Universes are used to do type- and trait-checking around these
+    /// "forall" binders (also called **universal quantification**). The
+    /// idea is that when, in the body of `bar`, we refer to `T` as a
+    /// type, we aren't referring to any type in particular, but rather a
+    /// kind of "fresh" type that is distinct from all other types we have
+    /// actually declared. This is called a **placeholder** type, and we
+    /// use universes to talk about this. In other words, a type name in
+    /// universe 0 always corresponds to some "ground" type that the user
+    /// declared, but a type name in a non-zero universe is a placeholder
+    /// type -- an idealized representative of "types in general" that we
+    /// use for checking generic functions.
     pub struct UniverseIndex {
         DEBUG_FORMAT = "U{}",
     }

src/librustc/ty/sty.rs

@@ -1082,46 +1082,46 @@ impl<'a, 'gcx, 'tcx> ParamConst {
     }
 }
 
-/// A [De Bruijn index][dbi] is a standard means of representing
-/// regions (and perhaps later types) in a higher-ranked setting. In
-/// particular, imagine a type like this:
-///
-///     for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
-///     ^          ^            |        |         |
-///     |          |            |        |         |
-///     |          +------------+ 0      |         |
-///     |                                |         |
-///     +--------------------------------+ 1       |
-///     |                                          |
-///     +------------------------------------------+ 0
-///
-/// In this type, there are two binders (the outer fn and the inner
-/// fn). We need to be able to determine, for any given region, which
-/// fn type it is bound by, the inner or the outer one. There are
-/// various ways you can do this, but a De Bruijn index is one of the
-/// more convenient and has some nice properties. The basic idea is to
-/// count the number of binders, inside out. Some examples should help
-/// clarify what I mean.
-///
-/// Let's start with the reference type `&'b isize` that is the first
-/// argument to the inner function. This region `'b` is assigned a De
-/// Bruijn index of 0, meaning "the innermost binder" (in this case, a
-/// fn). The region `'a` that appears in the second argument type (`&'a
-/// isize`) would then be assigned a De Bruijn index of 1, meaning "the
-/// second-innermost binder". (These indices are written on the arrays
-/// in the diagram).
-///
-/// What is interesting is that De Bruijn index attached to a particular
-/// variable will vary depending on where it appears. For example,
-/// the final type `&'a char` also refers to the region `'a` declared on
-/// the outermost fn. But this time, this reference is not nested within
-/// any other binders (i.e., it is not an argument to the inner fn, but
-/// rather the outer one). Therefore, in this case, it is assigned a
-/// De Bruijn index of 0, because the innermost binder in that location
-/// is the outer fn.
-///
-/// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
 newtype_index! {
+    /// A [De Bruijn index][dbi] is a standard means of representing
+    /// regions (and perhaps later types) in a higher-ranked setting. In
+    /// particular, imagine a type like this:
+    ///
+    ///     for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
+    ///     ^          ^            |        |         |
+    ///     |          |            |        |         |
+    ///     |          +------------+ 0      |         |
+    ///     |                                |         |
+    ///     +--------------------------------+ 1       |
+    ///     |                                          |
+    ///     +------------------------------------------+ 0
+    ///
+    /// In this type, there are two binders (the outer fn and the inner
+    /// fn). We need to be able to determine, for any given region, which
+    /// fn type it is bound by, the inner or the outer one. There are
+    /// various ways you can do this, but a De Bruijn index is one of the
+    /// more convenient and has some nice properties. The basic idea is to
+    /// count the number of binders, inside out. Some examples should help
+    /// clarify what I mean.
+    ///
+    /// Let's start with the reference type `&'b isize` that is the first
+    /// argument to the inner function. This region `'b` is assigned a De
+    /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
+    /// fn). The region `'a` that appears in the second argument type (`&'a
+    /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
+    /// second-innermost binder". (These indices are written on the arrays
+    /// in the diagram).
+    ///
+    /// What is interesting is that De Bruijn index attached to a particular
+    /// variable will vary depending on where it appears. For example,
+    /// the final type `&'a char` also refers to the region `'a` declared on
+    /// the outermost fn. But this time, this reference is not nested within
+    /// any other binders (i.e., it is not an argument to the inner fn, but
+    /// rather the outer one). Therefore, in this case, it is assigned a
+    /// De Bruijn index of 0, because the innermost binder in that location
+    /// is the outer fn.
+    ///
+    /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
     pub struct DebruijnIndex {
         DEBUG_FORMAT = "DebruijnIndex({})",
         const INNERMOST = 0,

src/librustc_data_structures/indexed_vec.rs

@@ -58,9 +58,10 @@ macro_rules! newtype_index {
     // ---- public rules ----
 
     // Use default constants
-    ($v:vis struct $name:ident { .. }) => (
+    ($(#[$attrs:meta])* $v:vis struct $name:ident { .. }) => (
         newtype_index!(
             // Leave out derives marker so we can use its absence to ensure it comes first
+            @attrs        [$(#[$attrs])*]
             @type         [$name]
             // shave off 256 indices at the end to allow space for packing these indices into enums
             @max          [0xFFFF_FF00]
@@ -69,9 +70,10 @@ macro_rules! newtype_index {
     );
 
     // Define any constants
-    ($v:vis struct $name:ident { $($tokens:tt)+ }) => (
+    ($(#[$attrs:meta])* $v:vis struct $name:ident { $($tokens:tt)+ }) => (
         newtype_index!(
             // Leave out derives marker so we can use its absence to ensure it comes first
+            @attrs        [$(#[$attrs])*]
             @type         [$name]
             // shave off 256 indices at the end to allow space for packing these indices into enums
             @max          [0xFFFF_FF00]
@@ -84,10 +86,12 @@ macro_rules! newtype_index {
 
     // Base case, user-defined constants (if any) have already been defined
     (@derives      [$($derives:ident,)*]
+     @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]) => (
+        $(#[$attrs])*
         #[derive(Copy, PartialEq, Eq, Hash, PartialOrd, Ord, $($derives),*)]
         #[rustc_layout_scalar_valid_range_end($max)]
         $v struct $type {
@@ -317,7 +321,8 @@ macro_rules! newtype_index {
 
     // By not including the @derives marker in this list nor in the default args, we can force it
     // to come first if it exists. When encodable isn't custom, add serialization traits by default.
-    (@type         [$type:ident]
+    (@attrs        [$(#[$attrs:meta])*]
+     @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
@@ -325,6 +330,7 @@ macro_rules! newtype_index {
                    $($tokens:tt)*) => (
         newtype_index!(
             @derives      [$($derives,)+ RustcEncodable,]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -335,7 +341,8 @@ macro_rules! newtype_index {
 
     // The case where no derives are added, but encodable is overridden. Don't
     // derive serialization traits
-    (@type         [$type:ident]
+    (@attrs        [$(#[$attrs:meta])*]
+     @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
@@ -343,6 +350,7 @@ macro_rules! newtype_index {
                    $($tokens:tt)*) => (
         newtype_index!(
             @derives      []
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -351,13 +359,15 @@ macro_rules! newtype_index {
     );
 
     // The case where no derives are added, add serialization derives by default
-    (@type         [$type:ident]
+    (@attrs        [$(#[$attrs:meta])*]
+     @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    $($tokens:tt)*) => (
         newtype_index!(
             @derives      [RustcEncodable,]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -384,6 +394,7 @@ macro_rules! newtype_index {
 
     // Rewrite final without comma to one that includes comma
     (@derives      [$($derives:ident,)*]
+     @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
@@ -391,6 +402,7 @@ macro_rules! newtype_index {
                    $name:ident = $constant:expr) => (
         newtype_index!(
             @derives      [$($derives,)*]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -400,6 +412,7 @@ macro_rules! newtype_index {
 
     // Rewrite final const without comma to one that includes comma
     (@derives      [$($derives:ident,)*]
+     @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$_max:expr]
      @vis          [$v:vis]
@@ -408,6 +421,7 @@ macro_rules! newtype_index {
                    const $name:ident = $constant:expr) => (
         newtype_index!(
             @derives      [$($derives,)*]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -417,6 +431,7 @@ macro_rules! newtype_index {
 
     // Replace existing default for max
     (@derives      [$($derives:ident,)*]
+     @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$_max:expr]
      @vis          [$v:vis]
@@ -425,6 +440,7 @@ macro_rules! newtype_index {
                    $($tokens:tt)*) => (
         newtype_index!(
             @derives      [$($derives,)*]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -434,6 +450,7 @@ macro_rules! newtype_index {
 
     // Replace existing default for debug_format
     (@derives      [$($derives:ident,)*]
+     @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
@@ -442,6 +459,7 @@ macro_rules! newtype_index {
                    $($tokens:tt)*) => (
         newtype_index!(
             @derives      [$($derives,)*]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
@@ -451,6 +469,7 @@ macro_rules! newtype_index {
 
     // Assign a user-defined constant
     (@derives      [$($derives:ident,)*]
+     @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
@@ -462,6 +481,7 @@ macro_rules! newtype_index {
         pub const $name: $type = $type::from_u32_const($constant);
         newtype_index!(
             @derives      [$($derives,)*]
+            @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]

src/librustc_lint/builtin.rs

@@ -36,7 +36,7 @@ use syntax::tokenstream::{TokenTree, TokenStream};
 use syntax::ast;
 use syntax::ptr::P;
 use syntax::ast::Expr;
-use syntax::attr;
+use syntax::attr::{self, HasAttrs};
 use syntax::source_map::Spanned;
 use syntax::edition::Edition;
 use syntax::feature_gate::{AttributeGate, AttributeTemplate, AttributeType};
@@ -802,7 +802,14 @@ impl LintPass for UnusedDocComment {
 }
 
 impl UnusedDocComment {
-    fn warn_if_doc(&self, cx: &EarlyContext, attrs: &[ast::Attribute]) {
+    fn warn_if_doc(
+        &self,
+        cx: &EarlyContext<'_>,
+        node_span: Span,
+        node_kind: &str,
+        is_macro_expansion: bool,
+        attrs: &[ast::Attribute]
+    ) {
         let mut attrs = attrs.into_iter().peekable();
 
         // Accumulate a single span for sugared doc comments.
@@ -825,27 +832,51 @@ impl UnusedDocComment {
             let span = sugared_span.take().unwrap_or_else(|| attr.span);
 
             if attr.name() == "doc" {
-                cx.struct_span_lint(
+                let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
-                    UNUSED_DOC_COMMENTS,
+
-                    span,
+                err.span_label(
-                    "doc comment not used by rustdoc",
+                    node_span,
-                ).emit();
+                    format!("rustdoc does not generate documentation for {}", node_kind)
+                );
+
+                if is_macro_expansion {
+                    err.help("to document an item produced by a macro, \
+                              the macro must produce the documentation as part of its expansion");
+                }
+
+                err.emit();
             }
         }
     }
 }
 
 impl EarlyLintPass for UnusedDocComment {
-    fn check_local(&mut self, cx: &EarlyContext<'_>, decl: &ast::Local) {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
-        self.warn_if_doc(cx, &decl.attrs);
+        if let ast::ItemKind::Mac(..) = item.node {
+            self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
+        }
+    }
+
+    fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
+        let (kind, is_macro_expansion) = match stmt.node {
+            ast::StmtKind::Local(..) => ("statements", false),
+            ast::StmtKind::Item(..) => ("inner items", false),
+            ast::StmtKind::Mac(..) => ("macro expansions", true),
+            // expressions will be reported by `check_expr`.
+            ast::StmtKind::Semi(..) |
+            ast::StmtKind::Expr(..) => return,
+        };
+
+        self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.node.attrs());
     }
 
     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
-        self.warn_if_doc(cx, &arm.attrs);
+        let arm_span = arm.pats[0].span.with_hi(arm.body.span.hi());
+        self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
     }
 
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
-        self.warn_if_doc(cx, &expr.attrs);
+        self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
     }
 }
 

src/librustc_lint/lib.rs

@@ -66,6 +66,7 @@ macro_rules! pre_expansion_lint_passes {
     ($macro:path, $args:tt) => (
         $macro!($args, [
             KeywordIdents: KeywordIdents,
+            UnusedDocComment: UnusedDocComment,
         ]);
     )
 }
@@ -77,7 +78,6 @@ macro_rules! early_lint_passes {
             UnusedImportBraces: UnusedImportBraces,
             UnsafeCode: UnsafeCode,
             AnonymousParameters: AnonymousParameters,
-            UnusedDocComment: UnusedDocComment,
             EllipsisInclusiveRangePatterns: EllipsisInclusiveRangePatterns,
             NonCamelCaseTypes: NonCamelCaseTypes,
             DeprecatedAttr: DeprecatedAttr::new(),

src/librustc_mir/borrow_check/nll/region_infer/values.rs

@@ -116,14 +116,14 @@ impl RegionValueElements {
     }
 }
 
-/// A single integer representing a `Location` in the MIR control-flow
-/// graph. Constructed efficiently from `RegionValueElements`.
 newtype_index! {
+    /// A single integer representing a `Location` in the MIR control-flow
+    /// graph. Constructed efficiently from `RegionValueElements`.
     pub struct PointIndex { DEBUG_FORMAT = "PointIndex({})" }
 }
 
-/// A single integer representing a `ty::Placeholder`.
 newtype_index! {
+    /// A single integer representing a `ty::Placeholder`.
     pub struct PlaceholderIndex { DEBUG_FORMAT = "PlaceholderIndex({})" }
 }
 

src/librustc_mir/dataflow/move_paths/mod.rs

@@ -23,7 +23,7 @@ pub(crate) mod indexes {
     use rustc_data_structures::indexed_vec::Idx;
 
     macro_rules! new_index {
-        ($Index:ident, $debug_name:expr) => {
+        ($(#[$attrs:meta])* $Index:ident, $debug_name:expr) => {
             #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
             pub struct $Index(NonZeroUsize);
 
@@ -44,17 +44,29 @@ pub(crate) mod indexes {
         }
     }
 
+    new_index!(
         /// Index into MovePathData.move_paths
-    new_index!(MovePathIndex, "mp");
+        MovePathIndex,
+        "mp"
+    );
 
+    new_index!(
         /// Index into MoveData.moves.
-    new_index!(MoveOutIndex, "mo");
+        MoveOutIndex,
+        "mo"
+    );
 
+    new_index!(
         /// Index into MoveData.inits.
-    new_index!(InitIndex, "in");
+        InitIndex,
+        "in"
+    );
 
+    new_index!(
         /// Index into Borrows.locations
-    new_index!(BorrowIndex, "bw");
+        BorrowIndex,
+        "bw"
+    );
 }
 
 pub use self::indexes::MovePathIndex;

src/libstd/io/stdio.rs

@@ -11,15 +11,15 @@ use crate::sys::stdio;
 use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 use crate::thread::LocalKey;
 
-/// Stdout used by print! and println! macros
 thread_local! {
+    /// Stdout used by print! and println! macros
     static LOCAL_STDOUT: RefCell<Option<Box<dyn Write + Send>>> = {
         RefCell::new(None)
     }
 }
 
-/// Stderr used by eprint! and eprintln! macros, and panics
 thread_local! {
+    /// Stderr used by eprint! and eprintln! macros, and panics
     static LOCAL_STDERR: RefCell<Option<Box<dyn Write + Send>>> = {
         RefCell::new(None)
     }

src/test/ui/useless_comment.rs

@@ -1,24 +1,43 @@
+#![feature(stmt_expr_attributes)]
+
 #![deny(unused_doc_comments)]
 
+macro_rules! mac {
+    () => {}
+}
+
+/// foo //~ ERROR unused doc comment
+mac!();
+
 fn foo() {
-    /// a //~ ERROR doc comment not used by rustdoc
+    /// a //~ ERROR unused doc comment
     let x = 12;
 
-    /// multi-line //~ doc comment not used by rustdoc
+    /// multi-line //~ unused doc comment
     /// doc comment
     /// that is unused
     match x {
-        /// c //~ ERROR doc comment not used by rustdoc
+        /// c //~ ERROR unused doc comment
         1 => {},
         _ => {}
     }
 
-    /// foo //~ ERROR doc comment not used by rustdoc
+    /// foo //~ ERROR unused doc comment
     unsafe {}
 
-    #[doc = "foo"] //~ ERROR doc comment not used by rustdoc
+    #[doc = "foo"] //~ ERROR unused doc comment
-    #[doc = "bar"] //~ ERROR doc comment not used by rustdoc
+    #[doc = "bar"] //~ ERROR unused doc comment
     3;
+
+    /// bar //~ ERROR unused doc comment
+    mac!();
+
+    let x = /** comment */ 47; //~ ERROR unused doc comment
+
+    /// dox //~ ERROR unused doc comment
+    {
+
+    }
 }
 
 fn main() {

src/test/ui/useless_comment.stderr

@@ -1,46 +1,98 @@
-error: doc comment not used by rustdoc
+error: unused doc comment
-  --> $DIR/useless_comment.rs:4:5
+  --> $DIR/useless_comment.rs:9:1
    |
-LL |     /// a //~ ERROR doc comment not used by rustdoc
+LL | /// foo //~ ERROR unused doc comment
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | mac!();
+   | ------- rustdoc does not generate documentation for macro expansions
    |
 note: lint level defined here
-  --> $DIR/useless_comment.rs:1:9
+  --> $DIR/useless_comment.rs:3:9
    |
 LL | #![deny(unused_doc_comments)]
    |         ^^^^^^^^^^^^^^^^^^^
+   = help: to document an item produced by a macro, the macro must produce the documentation as part of its expansion
 
-error: doc comment not used by rustdoc
+error: unused doc comment
-  --> $DIR/useless_comment.rs:7:5
+  --> $DIR/useless_comment.rs:13:5
    |
-LL | /     /// multi-line //~ doc comment not used by rustdoc
+LL |     /// a //~ ERROR unused doc comment
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let x = 12;
+   |     ----------- rustdoc does not generate documentation for statements
+
+error: unused doc comment
+  --> $DIR/useless_comment.rs:16:5
+   |
+LL | /     /// multi-line //~ unused doc comment
 LL | |     /// doc comment
 LL | |     /// that is unused
    | |______________________^
+LL | /     match x {
+LL | |         /// c //~ ERROR unused doc comment
+LL | |         1 => {},
+LL | |         _ => {}
+LL | |     }
+   | |_____- rustdoc does not generate documentation for expressions
 
-error: doc comment not used by rustdoc
+error: unused doc comment
-  --> $DIR/useless_comment.rs:11:9
+  --> $DIR/useless_comment.rs:20:9
    |
-LL |         /// c //~ ERROR doc comment not used by rustdoc
+LL |         /// c //~ ERROR unused doc comment
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |         1 => {},
+   |         ------- rustdoc does not generate documentation for match arms
 
-error: doc comment not used by rustdoc
+error: unused doc comment
-  --> $DIR/useless_comment.rs:16:5
+  --> $DIR/useless_comment.rs:25:5
    |
-LL |     /// foo //~ ERROR doc comment not used by rustdoc
+LL |     /// foo //~ ERROR unused doc comment
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     unsafe {}
+   |     --------- rustdoc does not generate documentation for expressions
 
-error: doc comment not used by rustdoc
+error: unused doc comment
-  --> $DIR/useless_comment.rs:19:5
+  --> $DIR/useless_comment.rs:28:5
    |
-LL |     #[doc = "foo"] //~ ERROR doc comment not used by rustdoc
+LL |     #[doc = "foo"] //~ ERROR unused doc comment
    |     ^^^^^^^^^^^^^^
+LL |     #[doc = "bar"] //~ ERROR unused doc comment
+LL |     3;
+   |     - rustdoc does not generate documentation for expressions
 
-error: doc comment not used by rustdoc
+error: unused doc comment
-  --> $DIR/useless_comment.rs:20:5
+  --> $DIR/useless_comment.rs:29:5
    |
-LL |     #[doc = "bar"] //~ ERROR doc comment not used by rustdoc
+LL |     #[doc = "bar"] //~ ERROR unused doc comment
    |     ^^^^^^^^^^^^^^
+LL |     3;
+   |     - rustdoc does not generate documentation for expressions
 
-error: aborting due to 6 previous errors
+error: unused doc comment
+  --> $DIR/useless_comment.rs:32:5
+   |
+LL |     /// bar //~ ERROR unused doc comment
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     mac!();
+   |     ------- rustdoc does not generate documentation for macro expansions
+   |
+   = help: to document an item produced by a macro, the macro must produce the documentation as part of its expansion
+
+error: unused doc comment
+  --> $DIR/useless_comment.rs:35:13
+   |
+LL |     let x = /** comment */ 47; //~ ERROR unused doc comment
+   |             ^^^^^^^^^^^^^^ -- rustdoc does not generate documentation for expressions
+
+error: unused doc comment
+  --> $DIR/useless_comment.rs:37:5
+   |
+LL |       /// dox //~ ERROR unused doc comment
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | /     {
+LL | |
+LL | |     }
+   | |_____- rustdoc does not generate documentation for expressions
+
+error: aborting due to 10 previous errors