Auto merge of #40346 - jseyfried:path_and_tokenstream_attr, r=nrc

`TokenStream`-based attributes, paths in attribute and derive macro invocations

This PR
 - refactors `Attribute` to use  `Path` and `TokenStream` instead of `MetaItem`.
 - supports macro invocation paths for attribute procedural macros.
   - e.g. `#[::foo::attr_macro] struct S;`, `#[cfg_attr(all(), foo::attr_macro)] struct S;`
 - supports macro invocation paths for derive procedural macros.
   - e.g. `#[derive(foo::Bar, super::Baz)] struct S;`
 - supports arbitrary tokens as arguments to attribute procedural macros.
   - e.g. `#[foo::attr_macro arbitrary + tokens] struct S;`
 - supports using arbitrary tokens in "inert attributes" with derive procedural macros.
   - e.g. `#[derive(Foo)] struct S(#[inert arbitrary + tokens] i32);`
where `#[proc_macro_derive(Foo, attributes(inert))]`

r? @nrc

src/librustc/hir/check_attr.rs

@@ -120,11 +120,12 @@ impl<'a> CheckAttrVisitor<'a> {
     }
 
     fn check_attribute(&self, attr: &ast::Attribute, target: Target) {
-        let name: &str = &attr.name().as_str();
-        match name {
-            "inline" => self.check_inline(attr, target),
-            "repr" => self.check_repr(attr, target),
-            _ => (),
+        if let Some(name) = attr.name() {
+            match &*name.as_str() {
+                "inline" => self.check_inline(attr, target),
+                "repr" => self.check_repr(attr, target),
+                _ => (),
+            }
         }
     }
 }

src/librustc/hir/lowering.rs

@@ -1296,7 +1296,7 @@ impl<'a> LoweringContext<'a> {
         let attrs = self.lower_attrs(&i.attrs);
         let mut vis = self.lower_visibility(&i.vis);
         if let ItemKind::MacroDef(ref tts) = i.node {
-            if i.attrs.iter().any(|attr| attr.name() == "macro_export") {
+            if i.attrs.iter().any(|attr| attr.path == "macro_export") {
                 self.exported_macros.push(hir::MacroDef {
                     name: name, attrs: attrs, id: i.id, span: i.span, body: tts.clone().into(),
                 });

src/librustc/lint/context.rs

@@ -408,14 +408,14 @@ pub fn gather_attrs(attrs: &[ast::Attribute]) -> Vec<Result<(ast::Name, Level, S
 pub fn gather_attr(attr: &ast::Attribute) -> Vec<Result<(ast::Name, Level, Span), Span>> {
     let mut out = vec![];
 
-    let level = match Level::from_str(&attr.name().as_str()) {
+    let level = match attr.name().and_then(|name| Level::from_str(&name.as_str())) {
         None => return out,
         Some(lvl) => lvl,
     };
 
+    let meta = unwrap_or!(attr.meta(), return out);
     attr::mark_used(attr);
 
-    let meta = &attr.value;
     let metas = if let Some(metas) = meta.meta_item_list() {
         metas
     } else {

src/librustc/middle/stability.rs

@@ -197,7 +197,7 @@ impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
         } else {
             // Emit errors for non-staged-api crates.
             for attr in attrs {
-                let tag = attr.name();
+                let tag = unwrap_or!(attr.name(), continue);
                 if tag == "unstable" || tag == "stable" || tag == "rustc_deprecated" {
                     attr::mark_used(attr);
                     self.tcx.sess.span_err(attr.span(), "stability attributes may not be used \
@@ -402,7 +402,7 @@ impl<'a, 'tcx> Index<'tcx> {
 
         let mut is_staged_api = false;
         for attr in &krate.attrs {
-            if attr.name() == "stable" || attr.name() == "unstable" {
+            if attr.path == "stable" || attr.path == "unstable" {
                 is_staged_api = true;
                 break
             }

src/librustc/traits/error_reporting.rs

@@ -274,7 +274,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             .filter(|a| a.check_name("rustc_on_unimplemented"))
             .next()
         {
-            let err_sp = item.meta().span.substitute_dummy(span);
+            let err_sp = item.span.substitute_dummy(span);
             let trait_str = self.tcx.item_path_str(trait_ref.def_id);
             if let Some(istring) = item.value_str() {
                 let istring = &*istring.as_str();

src/librustc_incremental/calculate_svh/svh_visitor.rs

@@ -18,16 +18,15 @@ use syntax::abi::Abi;
 use syntax::ast::{self, Name, NodeId};
 use syntax::attr;
 use syntax::parse::token;
-use syntax::symbol::{Symbol, InternedString};
+use syntax::symbol::InternedString;
 use syntax_pos::{Span, NO_EXPANSION, COMMAND_LINE_EXPN, BytePos};
 use syntax::tokenstream;
 use rustc::hir;
 use rustc::hir::*;
 use rustc::hir::def::Def;
 use rustc::hir::def_id::DefId;
-use rustc::hir::intravisit as visit;
+use rustc::hir::intravisit::{self as visit, Visitor};
 use rustc::ty::TyCtxt;
-use rustc_data_structures::fnv;
 use std::hash::{Hash, Hasher};
 
 use super::def_path_hash::DefPathHashes;
@@ -559,7 +558,7 @@ macro_rules! hash_span {
     });
 }
 
-impl<'a, 'hash, 'tcx> visit::Visitor<'tcx> for StrictVersionHashVisitor<'a, 'hash, 'tcx> {
+impl<'a, 'hash, 'tcx> Visitor<'tcx> for StrictVersionHashVisitor<'a, 'hash, 'tcx> {
     fn nested_visit_map<'this>(&'this mut self) -> visit::NestedVisitorMap<'this, 'tcx> {
         if self.hash_bodies {
             visit::NestedVisitorMap::OnlyBodies(&self.tcx.hir)
@@ -960,50 +959,24 @@ impl<'a, 'hash, 'tcx> StrictVersionHashVisitor<'a, 'hash, 'tcx> {
         }
     }
 
-    fn hash_meta_item(&mut self, meta_item: &ast::MetaItem) {
-        debug!("hash_meta_item: st={:?}", self.st);
-
-        // ignoring span information, it doesn't matter here
-        self.hash_discriminant(&meta_item.node);
-        meta_item.name.as_str().len().hash(self.st);
-        meta_item.name.as_str().hash(self.st);
-
-        match meta_item.node {
-            ast::MetaItemKind::Word => {}
-            ast::MetaItemKind::NameValue(ref lit) => saw_lit(lit).hash(self.st),
-            ast::MetaItemKind::List(ref items) => {
-                // Sort subitems so the hash does not depend on their order
-                let indices = self.indices_sorted_by(&items, |p| {
-                    (p.name().map(Symbol::as_str), fnv::hash(&p.literal().map(saw_lit)))
-                });
-                items.len().hash(self.st);
-                for (index, &item_index) in indices.iter().enumerate() {
-                    index.hash(self.st);
-                    let nested_meta_item: &ast::NestedMetaItemKind = &items[item_index].node;
-                    self.hash_discriminant(nested_meta_item);
-                    match *nested_meta_item {
-                        ast::NestedMetaItemKind::MetaItem(ref meta_item) => {
-                            self.hash_meta_item(meta_item);
-                        }
-                        ast::NestedMetaItemKind::Literal(ref lit) => {
-                            saw_lit(lit).hash(self.st);
-                        }
-                    }
-                }
-            }
-        }
-    }
-
     pub fn hash_attributes(&mut self, attributes: &[ast::Attribute]) {
         debug!("hash_attributes: st={:?}", self.st);
         let indices = self.indices_sorted_by(attributes, |attr| attr.name());
 
         for i in indices {
             let attr = &attributes[i];
-            if !attr.is_sugared_doc &&
-               !IGNORED_ATTRIBUTES.contains(&&*attr.value.name().as_str()) {
+            match attr.name() {
+                Some(name) if IGNORED_ATTRIBUTES.contains(&&*name.as_str()) => continue,
+                _ => {}
+            };
+            if !attr.is_sugared_doc {
                 SawAttribute(attr.style).hash(self.st);
-                self.hash_meta_item(&attr.value);
+                for segment in &attr.path.segments {
+                    SawIdent(segment.identifier.name.as_str()).hash(self.st);
+                }
+                for tt in attr.tokens.trees() {
+                    self.hash_token_tree(&tt);
+                }
             }
         }
     }

src/librustc_incremental/persist/dirty_clean.rs

@@ -104,9 +104,9 @@ pub struct DirtyCleanVisitor<'a, 'tcx:'a> {
 
 impl<'a, 'tcx> DirtyCleanVisitor<'a, 'tcx> {
     fn dep_node(&self, attr: &Attribute, def_id: DefId) -> DepNode<DefId> {
-        for item in attr.meta_item_list().unwrap_or(&[]) {
+        for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
             if item.check_name(LABEL) {
-                let value = expect_associated_value(self.tcx, item);
+                let value = expect_associated_value(self.tcx, &item);
                 match DepNode::from_label_string(&value.as_str(), def_id) {
                     Ok(def_id) => return def_id,
                     Err(()) => {
@@ -331,9 +331,9 @@ fn check_config(tcx: TyCtxt, attr: &Attribute) -> bool {
     debug!("check_config(attr={:?})", attr);
     let config = &tcx.sess.parse_sess.config;
     debug!("check_config: config={:?}", config);
-    for item in attr.meta_item_list().unwrap_or(&[]) {
+    for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
         if item.check_name(CFG) {
-            let value = expect_associated_value(tcx, item);
+            let value = expect_associated_value(tcx, &item);
             debug!("check_config: searching for cfg {:?}", value);
             return config.contains(&(value, None));
         }

src/librustc_lint/builtin.rs

@@ -312,7 +312,7 @@ impl MissingDoc {
             }
         }
 
-        let has_doc = attrs.iter().any(|a| a.is_value_str() && a.name() == "doc");
+        let has_doc = attrs.iter().any(|a| a.is_value_str() && a.check_name("doc"));
         if !has_doc {
             cx.span_lint(MISSING_DOCS,
                          sp,
@@ -635,7 +635,7 @@ impl LintPass for DeprecatedAttr {
 
 impl EarlyLintPass for DeprecatedAttr {
     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
-        let name = attr.name();
+        let name = unwrap_or!(attr.name(), return);
         for &&(n, _, ref g) in &self.depr_attrs {
             if name == n {
                 if let &AttributeGate::Gated(Stability::Deprecated(link),
@@ -1121,8 +1121,8 @@ impl LintPass for UnstableFeatures {
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
     fn check_attribute(&mut self, ctx: &LateContext, attr: &ast::Attribute) {
-        if attr.meta().check_name("feature") {
-            if let Some(items) = attr.meta().meta_item_list() {
+        if attr.check_name("feature") {
+            if let Some(items) = attr.meta_item_list() {
                 for item in items {
                     ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
                 }

src/librustc_lint/lib.rs

@@ -38,6 +38,7 @@
 #![feature(slice_patterns)]
 #![feature(staged_api)]
 
+#[macro_use]
 extern crate syntax;
 #[macro_use]
 extern crate rustc;

src/librustc_lint/unused.rs

@@ -269,6 +269,7 @@ impl LintPass for UnusedAttributes {
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
     fn check_attribute(&mut self, cx: &LateContext, attr: &ast::Attribute) {
         debug!("checking attribute: {:?}", attr);
+        let name = unwrap_or!(attr.name(), return);
 
         // Note that check_name() marks the attribute as used if it matches.
         for &(ref name, ty, _) in BUILTIN_ATTRIBUTES {
@@ -294,13 +295,13 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
             cx.span_lint(UNUSED_ATTRIBUTES, attr.span, "unused attribute");
             // Is it a builtin attribute that must be used at the crate level?
             let known_crate = BUILTIN_ATTRIBUTES.iter()
-                .find(|&&(name, ty, _)| attr.name() == name && ty == AttributeType::CrateLevel)
+                .find(|&&(builtin, ty, _)| name == builtin && ty == AttributeType::CrateLevel)
                 .is_some();
 
             // Has a plugin registered this attribute as one which must be used at
             // the crate level?
             let plugin_crate = plugin_attributes.iter()
-                .find(|&&(ref x, t)| attr.name() == &**x && AttributeType::CrateLevel == t)
+                .find(|&&(ref x, t)| name == &**x && AttributeType::CrateLevel == t)
                 .is_some();
             if known_crate || plugin_crate {
                 let msg = match attr.style {

src/librustc_metadata/creader.rs

@@ -973,9 +973,11 @@ impl<'a> CrateLoader<'a> {
 
 impl<'a> CrateLoader<'a> {
     pub fn preprocess(&mut self, krate: &ast::Crate) {
-        for attr in krate.attrs.iter().filter(|m| m.name() == "link_args") {
-            if let Some(linkarg) = attr.value_str() {
-                self.cstore.add_used_link_args(&linkarg.as_str());
+        for attr in &krate.attrs {
+            if attr.path == "link_args" {
+                if let Some(linkarg) = attr.value_str() {
+                    self.cstore.add_used_link_args(&linkarg.as_str());
+                }
             }
         }
     }

src/librustc_metadata/cstore.rs

@@ -269,9 +269,12 @@ impl CrateMetadata {
     }
 
     pub fn is_staged_api(&self) -> bool {
-        self.get_item_attrs(CRATE_DEF_INDEX)
-            .iter()
-            .any(|attr| attr.name() == "stable" || attr.name() == "unstable")
+        for attr in self.get_item_attrs(CRATE_DEF_INDEX) {
+            if attr.path == "stable" || attr.path == "unstable" {
+                return true;
+            }
+        }
+        false
     }
 
     pub fn is_allocator(&self) -> bool {

src/librustc_passes/ast_validation.rs

@@ -241,12 +241,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             ItemKind::Mod(_) => {
                 // Ensure that `path` attributes on modules are recorded as used (c.f. #35584).
                 attr::first_attr_value_str_by_name(&item.attrs, "path");
-                if let Some(attr) =
-                        item.attrs.iter().find(|attr| attr.name() == "warn_directory_ownership") {
+                if item.attrs.iter().any(|attr| attr.check_name("warn_directory_ownership")) {
                     let lint = lint::builtin::LEGACY_DIRECTORY_OWNERSHIP;
                     let msg = "cannot declare a new module at this location";
                     self.session.add_lint(lint, item.id, item.span, msg.to_string());
-                    attr::mark_used(attr);
                 }
             }
             ItemKind::Union(ref vdata, _) => {

src/librustc_resolve/lib.rs

@@ -1165,6 +1165,7 @@ pub struct Resolver<'a> {
 
     privacy_errors: Vec<PrivacyError<'a>>,
     ambiguity_errors: Vec<AmbiguityError<'a>>,
+    gated_errors: FxHashSet<Span>,
     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
 
     arenas: &'a ResolverArenas<'a>,
@@ -1355,6 +1356,7 @@ impl<'a> Resolver<'a> {
 
             privacy_errors: Vec::new(),
             ambiguity_errors: Vec::new(),
+            gated_errors: FxHashSet(),
             disallowed_shadowing: Vec::new(),
 
             arenas: arenas,
@@ -3359,8 +3361,9 @@ impl<'a> Resolver<'a> {
         if self.proc_macro_enabled { return; }
 
         for attr in attrs {
-            let maybe_binding = self.builtin_macros.get(&attr.name()).cloned().or_else(|| {
-                let ident = Ident::with_empty_ctxt(attr.name());
+            let name = unwrap_or!(attr.name(), continue);
+            let maybe_binding = self.builtin_macros.get(&name).cloned().or_else(|| {
+                let ident = Ident::with_empty_ctxt(name);
                 self.resolve_lexical_macro_path_segment(ident, MacroNS, None).ok()
             });