Auto merge of #50030 - flip1995:rfc2103, r=petrochenkov

Implement tool_attributes feature (RFC 2103)

cc #44690

This is currently just a rebased and compiling (hopefully) version of #47773.

Let's see if travis likes this. I will add the implementation for `tool_lints` this week.

src/doc/unstable-book/src/language-features/tool-attributes.md

@@ -0,0 +1,26 @@
+# `tool_attributes`
+
+The tracking issue for this feature is: [#44690]
+
+[#44690]: https://github.com/rust-lang/rust/issues/44690
+
+------------------------
+
+Tool attributes let you use scoped attributes to control the behavior
+of certain tools.
+
+Currently tool names which can be appear in scoped attributes are restricted to
+`clippy` and `rustfmt`.
+
+## An example
+
+```rust
+#![feature(tool_attributes)]
+
+#[rustfmt::skip]
+fn foo() { println!("hello, world"); }
+
+fn main() {
+    foo();
+}
+```

src/librustc/hir/check_attr.rs

@@ -153,10 +153,7 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
         // ```
         let hints: Vec<_> = item.attrs
             .iter()
-            .filter(|attr| match attr.name() {
-                Some(name) => name == "repr",
-                None => false,
-            })
+            .filter(|attr| attr.name() == "repr")
             .filter_map(|attr| attr.meta_item_list())
             .flat_map(|hints| hints)
             .collect();
@@ -311,7 +308,7 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
 
     fn check_used(&self, item: &hir::Item, target: Target) {
         for attr in &item.attrs {
-            if attr.name().map(|name| name == "used").unwrap_or(false) && target != Target::Static {
+            if attr.name() == "used" && target != Target::Static {
                 self.tcx.sess
                     .span_err(attr.span, "attribute must be applied to a `static` variable");
             }

src/librustc/ich/impls_syntax.rs

@@ -199,8 +199,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for [ast::Attribute] {
         let filtered: AccumulateVec<[&ast::Attribute; 8]> = self
             .iter()
             .filter(|attr| {
-                !attr.is_sugared_doc &&
-                attr.name().map(|name| !hcx.is_ignored_attr(name)).unwrap_or(true)
+                !attr.is_sugared_doc && !hcx.is_ignored_attr(attr.name())
             })
             .collect();
 
@@ -211,12 +210,23 @@ impl<'a> HashStable<StableHashingContext<'a>> for [ast::Attribute] {
     }
 }
 
+impl<'a> HashStable<StableHashingContext<'a>> for ast::Path {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        self.segments.len().hash_stable(hcx, hasher);
+        for segment in &self.segments {
+            segment.ident.name.hash_stable(hcx, hasher);
+        }
+    }
+}
+
 impl<'a> HashStable<StableHashingContext<'a>> for ast::Attribute {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a>,
                                           hasher: &mut StableHasher<W>) {
         // Make sure that these have been filtered out.
-        debug_assert!(self.name().map(|name| !hcx.is_ignored_attr(name)).unwrap_or(true));
+        debug_assert!(!hcx.is_ignored_attr(self.name()));
         debug_assert!(!self.is_sugared_doc);
 
         let ast::Attribute {
@@ -229,10 +239,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ast::Attribute {
         } = *self;
 
         style.hash_stable(hcx, hasher);
-        path.segments.len().hash_stable(hcx, hasher);
-        for segment in &path.segments {
-            segment.ident.name.hash_stable(hcx, hasher);
-        }
+        path.hash_stable(hcx, hasher);
         for tt in tokens.trees() {
             tt.hash_stable(hcx, hasher);
         }

src/librustc/lint/levels.rs

@@ -198,7 +198,7 @@ impl<'a> LintLevelsBuilder<'a> {
                       "malformed lint attribute");
         };
         for attr in attrs {
-            let level = match attr.name().and_then(|name| Level::from_str(&name.as_str())) {
+            let level = match Level::from_str(&attr.name().as_str()) {
                 None => continue,
                 Some(lvl) => lvl,
             };
@@ -221,7 +221,7 @@ impl<'a> LintLevelsBuilder<'a> {
                         continue
                     }
                 };
-                let name = word.ident.name;
+                let name = word.name();
                 match store.check_lint_name(&name.as_str()) {
                     CheckLintNameResult::Ok(ids) => {
                         let src = LintSource::Node(name, li.span);
@@ -260,7 +260,7 @@ impl<'a> LintLevelsBuilder<'a> {
                                                 Some(li.span.into()),
                                                 &msg);
                         if name.as_str().chars().any(|c| c.is_uppercase()) {
-                            let name_lower = name.as_str().to_lowercase();
+                            let name_lower = name.as_str().to_lowercase().to_string();
                             if let CheckLintNameResult::NoLint =
                                     store.check_lint_name(&name_lower) {
                                 db.emit();

src/librustc/middle/stability.rs

@@ -205,7 +205,7 @@ impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
         } else {
             // Emit errors for non-staged-api crates.
             for attr in attrs {
-                let tag = unwrap_or!(attr.name(), continue);
+                let tag = attr.name();
                 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 \

src/librustc/session/config.rs

@@ -1683,7 +1683,7 @@ pub fn parse_cfgspecs(cfgspecs: Vec<String>) -> ast::CrateConfig {
                 early_error(ErrorOutputType::default(), &msg)
             }
 
-            (meta_item.ident.name, meta_item.value_str())
+            (meta_item.name(), meta_item.value_str())
         })
         .collect::<ast::CrateConfig>()
 }

src/librustc/traits/on_unimplemented.rs

@@ -190,7 +190,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
         for command in self.subcommands.iter().chain(Some(self)).rev() {
             if let Some(ref condition) = command.condition {
                 if !attr::eval_condition(condition, &tcx.sess.parse_sess, &mut |c| {
-                    options.contains(&(c.ident.name.as_str().to_string(),
+                    options.contains(&(c.name().as_str().to_string(),
                                       match c.value_str().map(|s| s.as_str().to_string()) {
                                           Some(s) => Some(s),
                                           None => None

src/librustc_driver/lib.rs

@@ -1060,7 +1060,7 @@ impl RustcDefaultCalls {
                     let mut cfgs = Vec::new();
                     for &(name, ref value) in sess.parse_sess.config.iter() {
                         let gated_cfg = GatedCfg::gate(&ast::MetaItem {
-                            ident: ast::Ident::with_empty_ctxt(name),
+                            ident: ast::Path::from_ident(name.to_ident()),
                             node: ast::MetaItemKind::Word,
                             span: DUMMY_SP,
                         });

src/librustc_incremental/assert_dep_graph.rs

@@ -110,7 +110,7 @@ impl<'a, 'tcx> IfThisChanged<'a, 'tcx> {
         for list_item in attr.meta_item_list().unwrap_or_default() {
             match list_item.word() {
                 Some(word) if value.is_none() =>
-                    value = Some(word.ident.name),
+                    value = Some(word.name()),
                 _ =>
                     // FIXME better-encapsulate meta_item (don't directly access `node`)
                     span_bug!(list_item.span(), "unexpected meta-item {:?}", list_item.node),

src/librustc_lint/builtin.rs

@@ -675,9 +675,8 @@ impl LintPass for DeprecatedAttr {
 
 impl EarlyLintPass for DeprecatedAttr {
     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
-        let name = unwrap_or!(attr.name(), return);
         for &&(n, _, ref g) in &self.depr_attrs {
-            if name == n {
+            if attr.name() == n {
                 if let &AttributeGate::Gated(Stability::Deprecated(link),
                                              ref name,
                                              ref reason,

src/librustc_lint/lib.rs

@@ -30,7 +30,6 @@
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
 
-#[macro_use]
 extern crate syntax;
 #[macro_use]
 extern crate rustc;

src/librustc_lint/unused.rs

@@ -192,8 +192,6 @@ 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 {
             match ty {
@@ -213,6 +211,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
             }
         }
 
+        let name = attr.name();
         if !attr::is_used(attr) {
             debug!("Emitting warning for: {:?}", attr);
             cx.span_lint(UNUSED_ATTRIBUTES, attr.span, "unused attribute");

src/librustc_resolve/build_reduced_graph.rs

@@ -706,7 +706,7 @@ impl<'a> Resolver<'a> {
                 match attr.meta_item_list() {
                     Some(names) => for attr in names {
                         if let Some(word) = attr.word() {
-                            imports.imports.push((word.ident.name, attr.span()));
+                            imports.imports.push((word.name(), attr.span()));
                         } else {
                             span_err!(self.session, attr.span(), E0466, "bad macro import");
                         }

src/librustc_resolve/macros.rs

@@ -209,7 +209,7 @@ impl<'a> base::Resolver for Resolver<'a> {
     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>, allow_derive: bool)
                               -> Option<ast::Attribute> {
         for i in 0..attrs.len() {
-            let name = unwrap_or!(attrs[i].name(), continue);
+            let name = attrs[i].name();
 
             if self.session.plugin_attributes.borrow().iter()
                     .any(|&(ref attr_nm, _)| name == &**attr_nm) {
@@ -231,7 +231,7 @@ impl<'a> base::Resolver for Resolver<'a> {
 
         // Check for legacy derives
         for i in 0..attrs.len() {
-            let name = unwrap_or!(attrs[i].name(), continue);
+            let name = attrs[i].name();
 
             if name == "derive" {
                 let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {