Rollup of 7 pull requests

compiler/rustc_expand/src/proc_macro_server.rs

@@ -411,6 +411,10 @@ impl server::FreeFunctions for Rustc<'_> {
     fn track_env_var(&mut self, var: &str, value: Option<&str>) {
         self.sess.env_depinfo.borrow_mut().insert((Symbol::intern(var), value.map(Symbol::intern)));
     }
+
+    fn track_path(&mut self, path: &str) {
+        self.sess.file_depinfo.borrow_mut().insert(Symbol::intern(path));
+    }
 }
 
 impl server::TokenStream for Rustc<'_> {

compiler/rustc_interface/src/passes.rs

@@ -28,18 +28,18 @@ use rustc_passes::{self, hir_stats, layout_test};
 use rustc_plugin_impl as plugin;
 use rustc_query_impl::Queries as TcxQueries;
 use rustc_resolve::{Resolver, ResolverArenas};
+use rustc_serialize::json;
 use rustc_session::config::{CrateType, Input, OutputFilenames, OutputType, PpMode, PpSourceMode};
 use rustc_session::lint;
 use rustc_session::output::{filename_for_input, filename_for_metadata};
 use rustc_session::search_paths::PathKind;
 use rustc_session::Session;
 use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::FileName;
 use rustc_trait_selection::traits;
 use rustc_typeck as typeck;
-use tracing::{info, warn};
-
-use rustc_serialize::json;
 use tempfile::Builder as TempFileBuilder;
+use tracing::{info, warn};
 
 use std::any::Any;
 use std::cell::RefCell;
@@ -594,6 +594,16 @@ fn write_out_deps(
             .map(|fmap| escape_dep_filename(&fmap.name.prefer_local().to_string()))
             .collect();
 
+        // Account for explicitly marked-to-track files
+        // (e.g. accessed in proc macros).
+        let file_depinfo = sess.parse_sess.file_depinfo.borrow();
+        let extra_tracked_files = file_depinfo.iter().map(|path_sym| {
+            let path = PathBuf::from(&*path_sym.as_str());
+            let file = FileName::from(path);
+            escape_dep_filename(&file.prefer_local().to_string())
+        });
+        files.extend(extra_tracked_files);
+
         if let Some(ref backend) = sess.opts.debugging_opts.codegen_backend {
             files.push(backend.to_string());
         }

compiler/rustc_lint/src/builtin.rs

@@ -984,13 +984,16 @@ impl EarlyLintPass for DeprecatedAttr {
 }
 
 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
+    use rustc_ast::token::CommentKind;
+
     let mut attrs = attrs.iter().peekable();
 
     // Accumulate a single span for sugared doc comments.
     let mut sugared_span: Option<Span> = None;
 
     while let Some(attr) = attrs.next() {
-        if attr.is_doc_comment() {
+        let is_doc_comment = attr.is_doc_comment();
+        if is_doc_comment {
             sugared_span =
                 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
         }
@@ -1001,13 +1004,21 @@ fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &
 
         let span = sugared_span.take().unwrap_or(attr.span);
 
-        if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
+        if is_doc_comment || cx.sess().check_name(attr, sym::doc) {
             cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
                 let mut err = lint.build("unused doc comment");
                 err.span_label(
                     node_span,
                     format!("rustdoc does not generate documentation for {}", node_kind),
                 );
+                match attr.kind {
+                    AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
+                        err.help("use `//` for a plain comment");
+                    }
+                    AttrKind::DocComment(CommentKind::Block, _) => {
+                        err.help("use `/* */` for a plain comment");
+                    }
+                }
                 err.emit();
             });
         }

compiler/rustc_session/src/parse.rs

@@ -133,6 +133,8 @@ pub struct ParseSess {
     pub reached_eof: Lock<bool>,
     /// Environment variables accessed during the build and their values when they exist.
     pub env_depinfo: Lock<FxHashSet<(Symbol, Option<Symbol>)>>,
+    /// File paths accessed during the build.
+    pub file_depinfo: Lock<FxHashSet<Symbol>>,
     /// All the type ascriptions expressions that have had a suggestion for likely path typo.
     pub type_ascription_path_suggestions: Lock<FxHashSet<Span>>,
     /// Whether cfg(version) should treat the current release as incomplete
@@ -165,6 +167,7 @@ impl ParseSess {
             symbol_gallery: SymbolGallery::default(),
             reached_eof: Lock::new(false),
             env_depinfo: Default::default(),
+            file_depinfo: Default::default(),
             type_ascription_path_suggestions: Default::default(),
             assume_incomplete_release: false,
             proc_macro_quoted_spans: Default::default(),

compiler/rustc_typeck/src/check/intrinsic.rs

@@ -65,6 +65,10 @@ fn equate_intrinsic_type<'tcx>(
 /// Returns the unsafety of the given intrinsic.
 pub fn intrinsic_operation_unsafety(intrinsic: Symbol) -> hir::Unsafety {
     match intrinsic {
+        // When adding a new intrinsic to this list,
+        // it's usually worth updating that intrinsic's documentation
+        // to note that it's safe to call, since
+        // safe extern fns are otherwise unprecedented.
         sym::abort
         | sym::size_of
         | sym::min_align_of