Eliminate the SessionGlobals from librustc_ast.

By moving `{known,used}_attrs` from `SessionGlobals` to `Session`. This
means they are accessed via the `Session`, rather than via TLS. A few
`Attr` methods and `librustc_ast` functions are now methods of
`Session`.

All of this required passing a `Session` to lots of functions that didn't
already have one. Some of these functions also had arguments removed, because
those arguments could be accessed directly via the `Session` argument.

`contains_feature_attr()` was dead, and is removed.

Some functions were moved from `librustc_ast` elsewhere because they now need
to access `Session`, which isn't available in that crate.
- `entry_point_type()` --> `librustc_builtin_macros`
- `global_allocator_spans()` --> `librustc_metadata`
- `is_proc_macro_attr()` --> `Session`

Author: nnethercote

Cargo.lock

@@ -3195,7 +3195,6 @@ dependencies = [
  "rustc_macros",
  "rustc_serialize",
  "rustc_span",
- "scoped-tls",
  "smallvec 1.4.0",
  "tracing",
 ]
@@ -3467,6 +3466,7 @@ dependencies = [
  "rustc_index",
  "rustc_macros",
  "rustc_serialize",
+ "rustc_session",
  "rustc_span",
  "rustc_target",
  "smallvec 1.4.0",

src/librustc_ast/Cargo.toml

@@ -12,7 +12,6 @@ doctest = false
 [dependencies]
 rustc_serialize = { path = "../librustc_serialize" }
 log = { package = "tracing", version = "0.1" }
-scoped-tls = "1.0"
 rustc_span = { path = "../librustc_span" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_index = { path = "../librustc_index" }

src/librustc_ast/attr/mod.rs

@@ -10,72 +10,30 @@ use crate::ptr::P;
 use crate::token::{self, CommentKind, Token};
 use crate::tokenstream::{DelimSpan, TokenStream, TokenTree, TreeAndJoint};
 
-use rustc_data_structures::sync::Lock;
 use rustc_index::bit_set::GrowableBitSet;
-use rustc_span::edition::{Edition, DEFAULT_EDITION};
 use rustc_span::source_map::{BytePos, Spanned};
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::Span;
 
-use log::debug;
 use std::iter;
 use std::ops::DerefMut;
 
-// Per-session global variables: this struct is stored in thread-local storage
-// in such a way that it is accessible without any kind of handle to all
-// threads within the compilation session, but is not accessible outside the
-// session.
-pub struct SessionGlobals {
-    used_attrs: Lock<GrowableBitSet<AttrId>>,
-    known_attrs: Lock<GrowableBitSet<AttrId>>,
-    span_session_globals: rustc_span::SessionGlobals,
-}
+pub struct MarkedAttrs(GrowableBitSet<AttrId>);
 
-impl SessionGlobals {
-    fn new(edition: Edition) -> SessionGlobals {
-        SessionGlobals {
-            // We have no idea how many attributes there will be, so just
-            // initiate the vectors with 0 bits. We'll grow them as necessary.
-            used_attrs: Lock::new(GrowableBitSet::new_empty()),
-            known_attrs: Lock::new(GrowableBitSet::new_empty()),
-            span_session_globals: rustc_span::SessionGlobals::new(edition),
-        }
+impl MarkedAttrs {
+    // We have no idea how many attributes there will be, so just
+    // initiate the vectors with 0 bits. We'll grow them as necessary.
+    pub fn new() -> Self {
+        MarkedAttrs(GrowableBitSet::new_empty())
     }
-}
-
-pub fn with_session_globals<R>(edition: Edition, f: impl FnOnce() -> R) -> R {
-    let ast_session_globals = SessionGlobals::new(edition);
-    SESSION_GLOBALS.set(&ast_session_globals, || {
-        rustc_span::SESSION_GLOBALS.set(&ast_session_globals.span_session_globals, f)
-    })
-}
-
-pub fn with_default_session_globals<R>(f: impl FnOnce() -> R) -> R {
-    with_session_globals(DEFAULT_EDITION, f)
-}
 
-scoped_tls::scoped_thread_local!(pub static SESSION_GLOBALS: SessionGlobals);
-
-pub fn mark_used(attr: &Attribute) {
-    debug!("marking {:?} as used", attr);
-    SESSION_GLOBALS.with(|session_globals| {
-        session_globals.used_attrs.lock().insert(attr.id);
-    });
-}
-
-pub fn is_used(attr: &Attribute) -> bool {
-    SESSION_GLOBALS.with(|session_globals| session_globals.used_attrs.lock().contains(attr.id))
-}
-
-pub fn mark_known(attr: &Attribute) {
-    debug!("marking {:?} as known", attr);
-    SESSION_GLOBALS.with(|session_globals| {
-        session_globals.known_attrs.lock().insert(attr.id);
-    });
-}
+    pub fn mark(&mut self, attr: &Attribute) {
+        self.0.insert(attr.id);
+    }
 
-pub fn is_known(attr: &Attribute) -> bool {
-    SESSION_GLOBALS.with(|session_globals| session_globals.known_attrs.lock().contains(attr.id))
+    pub fn is_marked(&self, attr: &Attribute) -> bool {
+        self.0.contains(attr.id)
+    }
 }
 
 pub fn is_known_lint_tool(m_item: Ident) -> bool {
@@ -173,21 +131,6 @@ impl Attribute {
         }
     }
 
-    /// Returns `true` if the attribute's path matches the argument.
-    /// If it matches, then the attribute is marked as used.
-    /// Should only be used by rustc, other tools can use `has_name` instead,
-    /// because only rustc is supposed to report the `unused_attributes` lint.
-    /// `MetaItem` and `NestedMetaItem` are produced by "lowering" an `Attribute`
-    /// and don't have identity, so they only has the `has_name` method,
-    /// and you need to mark the original `Attribute` as used when necessary.
-    pub fn check_name(&self, name: Symbol) -> bool {
-        let matches = self.has_name(name);
-        if matches {
-            mark_used(self);
-        }
-        matches
-    }
-
     /// For a single-segment attribute, returns its name; otherwise, returns `None`.
     pub fn ident(&self) -> Option<Ident> {
         match self.kind {
@@ -418,22 +361,6 @@ pub fn list_contains_name(items: &[NestedMetaItem], name: Symbol) -> bool {
     items.iter().any(|item| item.has_name(name))
 }
 
-pub fn contains_name(attrs: &[Attribute], name: Symbol) -> bool {
-    attrs.iter().any(|item| item.check_name(name))
-}
-
-pub fn find_by_name(attrs: &[Attribute], name: Symbol) -> Option<&Attribute> {
-    attrs.iter().find(|attr| attr.check_name(name))
-}
-
-pub fn filter_by_name(attrs: &[Attribute], name: Symbol) -> impl Iterator<Item = &Attribute> {
-    attrs.iter().filter(move |attr| attr.check_name(name))
-}
-
-pub fn first_attr_value_str_by_name(attrs: &[Attribute], name: Symbol) -> Option<Symbol> {
-    attrs.iter().find(|at| at.check_name(name)).and_then(|at| at.value_str())
-}
-
 impl MetaItem {
     fn token_trees_and_joints(&self) -> Vec<TreeAndJoint> {
         let mut idents = vec![];

src/librustc_ast/entry.rs

@@ -1,35 +1,7 @@
-use crate::ast::{Item, ItemKind};
-use crate::attr;
-use rustc_span::symbol::sym;
-
 pub enum EntryPointType {
     None,
     MainNamed,
     MainAttr,
     Start,
     OtherMain, // Not an entry point, but some other function named main
 }
-
-// Beware, this is duplicated in librustc_middle/middle/entry.rs, make sure to keep
-// them in sync.
-pub fn entry_point_type(item: &Item, depth: usize) -> EntryPointType {
-    match item.kind {
-        ItemKind::Fn(..) => {
-            if attr::contains_name(&item.attrs, sym::start) {
-                EntryPointType::Start
-            } else if attr::contains_name(&item.attrs, sym::main) {
-                EntryPointType::MainAttr
-            } else if item.ident.name == sym::main {
-                if depth == 1 {
-                    // This is a top-level function so can be 'main'
-                    EntryPointType::MainNamed
-                } else {
-                    EntryPointType::OtherMain
-                }
-            } else {
-                EntryPointType::None
-            }
-        }
-        _ => EntryPointType::None,
-    }
-}

src/librustc_ast/expand/allocator.rs

@@ -1,6 +1,4 @@
-use crate::{ast, attr, visit};
 use rustc_span::symbol::{sym, Symbol};
-use rustc_span::Span;
 
 #[derive(Clone, Copy)]
 pub enum AllocatorKind {
@@ -53,25 +51,3 @@ pub static ALLOCATOR_METHODS: &[AllocatorMethod] = &[
         output: AllocatorTy::ResultPtr,
     },
 ];
-
-pub fn global_allocator_spans(krate: &ast::Crate) -> Vec<Span> {
-    struct Finder {
-        name: Symbol,
-        spans: Vec<Span>,
-    }
-    impl<'ast> visit::Visitor<'ast> for Finder {
-        fn visit_item(&mut self, item: &'ast ast::Item) {
-            if item.ident.name == self.name
-                && attr::contains_name(&item.attrs, sym::rustc_std_internal_symbol)
-            {
-                self.spans.push(item.span);
-            }
-            visit::walk_item(self, item)
-        }
-    }
-
-    let name = Symbol::intern(&AllocatorKind::Global.fn_name(sym::alloc));
-    let mut f = Finder { name, spans: Vec::new() };
-    visit::walk_crate(&mut f, krate);
-    f.spans
-}

src/librustc_ast/expand/mod.rs

@@ -1,12 +1,3 @@
 //! Definitions shared by macros / syntax extensions and e.g. librustc_middle.
 
-use crate::ast::Attribute;
-use rustc_span::symbol::sym;
-
 pub mod allocator;
-
-pub fn is_proc_macro_attr(attr: &Attribute) -> bool {
-    [sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
-        .iter()
-        .any(|kind| attr.check_name(*kind))
-}

src/librustc_ast/lib.rs

@@ -42,7 +42,6 @@ pub mod util {
 
 pub mod ast;
 pub mod attr;
-pub use attr::{with_default_session_globals, with_session_globals, SESSION_GLOBALS};
 pub mod crate_disambiguator;
 pub mod entry;
 pub mod expand;

src/librustc_ast/util/comments/tests.rs

@@ -1,5 +1,5 @@
 use super::*;
-use crate::with_default_session_globals;
+use rustc_span::with_default_session_globals;
 
 #[test]
 fn line_doc_comments() {

src/librustc_ast/util/lev_distance/tests.rs

@@ -21,7 +21,7 @@ fn test_lev_distance() {
 
 #[test]
 fn test_find_best_match_for_name() {
-    use crate::with_default_session_globals;
+    use rustc_span::with_default_session_globals;
     with_default_session_globals(|| {
         let input = vec![Symbol::intern("aaab"), Symbol::intern("aaabc")];
         assert_eq!(

src/librustc_ast_lowering/item.rs

@@ -3,7 +3,6 @@ use super::{ImplTraitContext, ImplTraitPosition};
 use crate::Arena;
 
 use rustc_ast::ast::*;
-use rustc_ast::attr;
 use rustc_ast::node_id::NodeMap;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::{self, AssocCtxt, Visitor};
@@ -205,7 +204,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let attrs = self.lower_attrs(&i.attrs);
 
         if let ItemKind::MacroDef(MacroDef { ref body, macro_rules }) = i.kind {
-            if !macro_rules || attr::contains_name(&i.attrs, sym::macro_export) {
+            if !macro_rules || self.sess.contains_name(&i.attrs, sym::macro_export) {
                 let hir_id = self.lower_node_id(i.id);
                 let body = P(self.lower_mac_args(body));
                 self.exported_macros.push(hir::MacroDef {