From af46699f8104ba5257d0da56d3d817bf8fc751cf Mon Sep 17 00:00:00 2001
From: Aaron Hill <aa1ronham@gmail.com>
Date: Thu, 29 Jul 2021 12:00:41 -0500
Subject: Remove `Session.used_attrs` and move logic to `CheckAttrVisitor`

Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).

`Session.check_name` is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
`Attribute.has_name`

Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in `CheckAttrVisitor` for a particular attribute.

We no longer emit unused attribute warnings for the `#[rustc_dummy]`
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.

With this commit, a large source of global untracked state is removed.
---
 compiler/rustc_resolve/src/build_reduced_graph.rs |  6 +++---
 compiler/rustc_resolve/src/late/lifetimes.rs      | 10 +++++++---
 compiler/rustc_resolve/src/lib.rs                 |  5 ++---
 3 files changed, 12 insertions(+), 9 deletions(-)

(limited to 'compiler/rustc_resolve/src')

diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 178d727418d..c06ef08e0a8 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -1059,7 +1059,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         let mut import_all = None;
         let mut single_imports = Vec::new();
         for attr in &item.attrs {
-            if self.r.session.check_name(attr, sym::macro_use) {
+            if attr.has_name(sym::macro_use) {
                 if self.parent_scope.module.parent.is_some() {
                     struct_span_err!(
                         self.r.session,
@@ -1165,7 +1165,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     /// Returns `true` if this attribute list contains `macro_use`.
     fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
         for attr in attrs {
-            if self.r.session.check_name(attr, sym::macro_escape) {
+            if attr.has_name(sym::macro_escape) {
                 let msg = "`#[macro_escape]` is a deprecated synonym for `#[macro_use]`";
                 let mut err = self.r.session.struct_span_warn(attr.span, msg);
                 if let ast::AttrStyle::Inner = attr.style {
@@ -1173,7 +1173,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 } else {
                     err.emit();
                 }
-            } else if !self.r.session.check_name(attr, sym::macro_use) {
+            } else if !attr.has_name(sym::macro_use) {
                 continue;
             }
 
diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs
index d79fd910b7e..882d15cf892 100644
--- a/compiler/rustc_resolve/src/late/lifetimes.rs
+++ b/compiler/rustc_resolve/src/late/lifetimes.rs
@@ -2057,9 +2057,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                             if let Some(def_id) = parent_def_id.as_local() {
                                 let parent_hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
                                 // lifetimes in `derive` expansions don't count (Issue #53738)
-                                if self.tcx.hir().attrs(parent_hir_id).iter().any(|attr| {
-                                    self.tcx.sess.check_name(attr, sym::automatically_derived)
-                                }) {
+                                if self
+                                    .tcx
+                                    .hir()
+                                    .attrs(parent_hir_id)
+                                    .iter()
+                                    .any(|attr| attr.has_name(sym::automatically_derived))
+                                {
                                     continue;
                                 }
                             }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 7114fd33188..438a109f967 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -3382,9 +3382,8 @@ impl<'a> Resolver<'a> {
 
                 let parse_attrs = || {
                     let attrs = self.cstore().item_attrs(def_id, self.session);
-                    let attr = attrs
-                        .iter()
-                        .find(|a| self.session.check_name(a, sym::rustc_legacy_const_generics))?;
+                    let attr =
+                        attrs.iter().find(|a| a.has_name(sym::rustc_legacy_const_generics))?;
                     let mut ret = vec![];
                     for meta in attr.meta_item_list()? {
                         match meta.literal()?.kind {
-- 
cgit 1.4.1-3-g733a5