Rollup merge of #62243 - petrochenkov:macrodoc, r=eddyb

Improve documentation for built-in macros

This is the `libcore` part of #62086.
Right now the only effect is improved documentation.

The changes in the last few commits are required to make the `libcore` change compile successfully.

src/libcore/lib.rs

@@ -75,6 +75,7 @@
 #![feature(const_fn)]
 #![feature(const_fn_union)]
 #![feature(custom_inner_attributes)]
+#![feature(decl_macro)]
 #![feature(doc_cfg)]
 #![feature(doc_spotlight)]
 #![feature(extern_types)]

src/librustc/hir/lowering.rs

@@ -4010,7 +4010,7 @@ impl<'a> LoweringContext<'a> {
         let attrs = self.lower_attrs(&i.attrs);
         if let ItemKind::MacroDef(ref def) = i.node {
             if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) ||
-                              attr::contains_name(&i.attrs, sym::rustc_doc_only_macro) {
+                              attr::contains_name(&i.attrs, sym::rustc_builtin_macro) {
                 let body = self.lower_token_stream(def.stream());
                 let hir_id = self.lower_node_id(i.id);
                 self.exported_macros.push(hir::MacroDef {

src/librustc_privacy/lib.rs

@@ -28,6 +28,7 @@ use rustc_data_structures::fx::FxHashSet;
 use syntax::ast::Ident;
 use syntax::attr;
 use syntax::symbol::{kw, sym};
+use syntax_pos::hygiene::Transparency;
 use syntax_pos::Span;
 
 use std::{cmp, fmt, mem};
@@ -743,7 +744,7 @@ impl Visitor<'tcx> for EmbargoVisitor<'tcx> {
     }
 
     fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
-        if md.legacy {
+        if attr::find_transparency(&md.attrs, md.legacy).0 != Transparency::Opaque {
             self.update(md.hir_id, Some(AccessLevel::Public));
             return
         }

src/librustc_resolve/build_reduced_graph.rs

@@ -770,27 +770,33 @@ impl<'a> Resolver<'a> {
     }
 
     pub fn get_macro(&mut self, res: Res) -> Lrc<SyntaxExtension> {
+        self.opt_get_macro(res).expect("expected `DefKind::Macro` or `Res::NonMacroAttr`")
+    }
+
+    crate fn opt_get_macro(&mut self, res: Res) -> Option<Lrc<SyntaxExtension>> {
         let def_id = match res {
+            Res::Def(DefKind::Macro(MacroKind::ProcMacroStub), _) =>
+                return Some(self.non_macro_attr(true)), // some dummy extension
             Res::Def(DefKind::Macro(..), def_id) => def_id,
             Res::NonMacroAttr(attr_kind) =>
-                return self.non_macro_attr(attr_kind == NonMacroAttrKind::Tool),
-            _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
+                return Some(self.non_macro_attr(attr_kind == NonMacroAttrKind::Tool)),
+            _ => return None,
         };
         if let Some(ext) = self.macro_map.get(&def_id) {
-            return ext.clone();
+            return Some(ext.clone());
         }
 
         let macro_def = match self.cstore.load_macro_untracked(def_id, &self.session) {
             LoadedMacro::MacroDef(macro_def) => macro_def,
-            LoadedMacro::ProcMacro(ext) => return ext,
+            LoadedMacro::ProcMacro(ext) => return Some(ext),
         };
 
         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
                                                &self.session.features_untracked(),
                                                &macro_def,
                                                self.cstore.crate_edition_untracked(def_id.krate)));
         self.macro_map.insert(def_id, ext.clone());
-        ext
+        Some(ext)
     }
 
     /// Ensures that the reduced graph rooted at the given external module

src/librustc_resolve/macros.rs

@@ -1106,6 +1106,19 @@ impl<'a> Resolver<'a> {
         });
     }
 
+    crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
+        // Reserve some names that are not quite covered by the general check
+        // performed on `Resolver::builtin_attrs`.
+        if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
+            let macro_kind = self.opt_get_macro(res).map(|ext| ext.macro_kind());
+            if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
+                self.session.span_err(
+                    ident.span, &format!("name `{}` is reserved in attribute namespace", ident)
+                );
+            }
+        }
+    }
+
     pub fn define_macro(&mut self,
                         item: &ast::Item,
                         expansion: Mark,
@@ -1117,13 +1130,14 @@ impl<'a> Resolver<'a> {
         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
                                                &self.session.features_untracked(),
                                                item, self.session.edition()));
+        let macro_kind = ext.macro_kind();
+        let res = Res::Def(DefKind::Macro(macro_kind), def_id);
         self.macro_map.insert(def_id, ext);
 
         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
         if def.legacy {
             let ident = ident.modern();
             self.macro_names.insert(ident);
-            let res = Res::Def(DefKind::Macro(MacroKind::Bang), def_id);
             let is_macro_export = attr::contains_name(&item.attrs, sym::macro_export);
             let vis = if is_macro_export {
                 ty::Visibility::Public
@@ -1142,14 +1156,11 @@ impl<'a> Resolver<'a> {
                 self.define(module, ident, MacroNS,
                             (res, vis, item.span, expansion, IsMacroExport));
             } else {
-                if !attr::contains_name(&item.attrs, sym::rustc_doc_only_macro) {
-                    self.check_reserved_macro_name(ident, MacroNS);
-                }
+                self.check_reserved_macro_name(ident, res);
                 self.unused_macros.insert(def_id);
             }
         } else {
             let module = self.current_module;
-            let res = Res::Def(DefKind::Macro(MacroKind::Bang), def_id);
             let vis = self.resolve_visibility(&item.vis);
             if vis != ty::Visibility::Public {
                 self.unused_macros.insert(def_id);

src/librustc_resolve/resolve_imports.rs

@@ -29,7 +29,7 @@ use rustc::{bug, span_bug};
 use syntax::ast::{self, Ident, Name, NodeId, CRATE_NODE_ID};
 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
 use syntax::ext::hygiene::Mark;
-use syntax::symbol::{kw, sym};
+use syntax::symbol::kw;
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::{struct_span_err, unwrap_or};
 use syntax_pos::{MultiSpan, Span};
@@ -492,35 +492,25 @@ impl<'a> Resolver<'a> {
         })
     }
 
-    crate fn check_reserved_macro_name(&self, ident: Ident, ns: Namespace) {
-        // Reserve some names that are not quite covered by the general check
-        // performed on `Resolver::builtin_attrs`.
-        if ns == MacroNS &&
-           (ident.name == sym::cfg || ident.name == sym::cfg_attr ||
-            ident.name == sym::derive) {
-            self.session.span_err(ident.span,
-                                  &format!("name `{}` is reserved in macro namespace", ident));
-        }
-    }
-
     // Define the name or return the existing binding if there is a collision.
     pub fn try_define(&mut self,
                       module: Module<'a>,
                       ident: Ident,
                       ns: Namespace,
                       binding: &'a NameBinding<'a>)
                       -> Result<(), &'a NameBinding<'a>> {
-        self.check_reserved_macro_name(ident, ns);
+        let res = binding.res();
+        self.check_reserved_macro_name(ident, res);
         self.set_binding_parent_module(binding, module);
         self.update_resolution(module, ident, ns, |this, resolution| {
             if let Some(old_binding) = resolution.binding {
-                if binding.res() == Res::Err {
+                if res == Res::Err {
                     // Do not override real bindings with `Res::Err`s from error recovery.
                     return Ok(());
                 }
                 match (old_binding.is_glob_import(), binding.is_glob_import()) {
                     (true, true) => {
-                        if binding.res() != old_binding.res() {
+                        if res != old_binding.res() {
                             resolution.binding = Some(this.ambiguity(AmbiguityKind::GlobVsGlob,
                                                                      old_binding, binding));
                         } else if !old_binding.vis.is_at_least(binding.vis, &*this) {

src/libstd/macros.rs

@@ -410,7 +410,7 @@ mod builtin {
     ///
     /// [`panic!`]: ../std/macro.panic.html
     #[stable(feature = "compile_error_macro", since = "1.20.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! compile_error {
         ($msg:expr) => ({ /* compiler built-in */ });
         ($msg:expr,) => ({ /* compiler built-in */ });
@@ -462,7 +462,7 @@ mod builtin {
     /// assert_eq!(s, format!("hello {}", "world"));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! format_args {
         ($fmt:expr) => ({ /* compiler built-in */ });
         ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ });
@@ -500,7 +500,7 @@ mod builtin {
     /// error: what's that?!
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! env {
         ($name:expr) => ({ /* compiler built-in */ });
         ($name:expr,) => ({ /* compiler built-in */ });
@@ -526,7 +526,7 @@ mod builtin {
     /// println!("the secret key might be: {:?}", key);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! option_env {
         ($name:expr) => ({ /* compiler built-in */ });
         ($name:expr,) => ({ /* compiler built-in */ });
@@ -557,7 +557,7 @@ mod builtin {
     /// # }
     /// ```
     #[unstable(feature = "concat_idents_macro", issue = "29599")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! concat_idents {
         ($($e:ident),+) => ({ /* compiler built-in */ });
         ($($e:ident,)+) => ({ /* compiler built-in */ });
@@ -579,7 +579,7 @@ mod builtin {
     /// assert_eq!(s, "test10btrue");
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! concat {
         ($($e:expr),*) => ({ /* compiler built-in */ });
         ($($e:expr,)*) => ({ /* compiler built-in */ });
@@ -607,7 +607,7 @@ mod builtin {
     /// println!("defined on line: {}", current_line);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! line { () => ({ /* compiler built-in */ }) }
 
     /// Expands to the column number at which it was invoked.
@@ -632,7 +632,7 @@ mod builtin {
     /// println!("defined on column: {}", current_col);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! column { () => ({ /* compiler built-in */ }) }
 
     /// Expands to the file name in which it was invoked.
@@ -656,7 +656,7 @@ mod builtin {
     /// println!("defined in file: {}", this_file);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! file { () => ({ /* compiler built-in */ }) }
 
     /// Stringifies its arguments.
@@ -675,7 +675,7 @@ mod builtin {
     /// assert_eq!(one_plus_one, "1 + 1");
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! stringify { ($($t:tt)*) => ({ /* compiler built-in */ }) }
 
     /// Includes a utf8-encoded file as a string.
@@ -709,7 +709,7 @@ mod builtin {
     ///
     /// Compiling 'main.rs' and running the resulting binary will print "adiós".
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! include_str {
         ($file:expr) => ({ /* compiler built-in */ });
         ($file:expr,) => ({ /* compiler built-in */ });
@@ -746,7 +746,7 @@ mod builtin {
     ///
     /// Compiling 'main.rs' and running the resulting binary will print "adiós".
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! include_bytes {
         ($file:expr) => ({ /* compiler built-in */ });
         ($file:expr,) => ({ /* compiler built-in */ });
@@ -770,7 +770,7 @@ mod builtin {
     /// test::foo();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! module_path { () => ({ /* compiler built-in */ }) }
 
     /// Evaluates boolean combinations of configuration flags at compile-time.
@@ -794,7 +794,7 @@ mod builtin {
     /// };
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! cfg { ($($cfg:tt)*) => ({ /* compiler built-in */ }) }
 
     /// Parses a file as an expression or an item according to the context.
@@ -837,7 +837,7 @@ mod builtin {
     /// Compiling 'main.rs' and running the resulting binary will print
     /// "🙈🙊🙉🙈🙊🙉".
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! include {
         ($file:expr) => ({ /* compiler built-in */ });
         ($file:expr,) => ({ /* compiler built-in */ });
@@ -889,7 +889,7 @@ mod builtin {
     /// assert!(a + b == 30, "a = {}, b = {}", a, b);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_doc_only_macro]
+    #[rustc_builtin_macro]
     macro_rules! assert {
         ($cond:expr) => ({ /* compiler built-in */ });
         ($cond:expr,) => ({ /* compiler built-in */ });

src/libsyntax/attr/builtin.rs

@@ -5,6 +5,7 @@ use crate::feature_gate::{Features, GatedCfg};
 use crate::parse::ParseSess;
 
 use errors::{Applicability, Handler};
+use syntax_pos::hygiene::Transparency;
 use syntax_pos::{symbol::Symbol, symbol::sym, Span};
 
 use super::{mark_used, MetaItemKind};
@@ -854,3 +855,35 @@ fn int_type_of_word(s: Symbol) -> Option<IntType> {
         _ => None
     }
 }
+
+pub enum TransparencyError {
+    UnknownTransparency(Symbol, Span),
+    MultipleTransparencyAttrs(Span, Span),
+}
+
+pub fn find_transparency(
+    attrs: &[Attribute], is_legacy: bool
+) -> (Transparency, Option<TransparencyError>) {
+    let mut transparency = None;
+    let mut error = None;
+    for attr in attrs {
+        if attr.check_name(sym::rustc_macro_transparency) {
+            if let Some((_, old_span)) = transparency {
+                error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
+                break;
+            } else if let Some(value) = attr.value_str() {
+                transparency = Some((match &*value.as_str() {
+                    "transparent" => Transparency::Transparent,
+                    "semitransparent" => Transparency::SemiTransparent,
+                    "opaque" => Transparency::Opaque,
+                    _ => {
+                        error = Some(TransparencyError::UnknownTransparency(value, attr.span));
+                        continue;
+                    }
+                }, attr.span));
+            }
+        }
+    }
+    let fallback = if is_legacy { Transparency::SemiTransparent } else { Transparency::Opaque };
+    (transparency.map_or(fallback, |t| t.0), error)
+}

src/libsyntax/attr/mod.rs

@@ -2,11 +2,7 @@
 
 mod builtin;
 
-pub use builtin::{
-    cfg_matches, contains_feature_attr, eval_condition, find_crate_name, find_deprecation,
-    find_repr_attrs, find_stability, find_unwind_attr, Deprecation, InlineAttr, OptimizeAttr,
-    IntType, ReprAttr, RustcDeprecation, Stability, StabilityLevel, UnwindAttr,
-};
+pub use builtin::*;
 pub use IntType::*;
 pub use ReprAttr::*;
 pub use StabilityLevel::*;