Auto merge of #37824 - jseyfried:symbols, r=eddyb

Clean up `ast::Attribute`, `ast::CrateConfig`, and string interning

This PR
 - removes `ast::Attribute_` (changing `Attribute` from `Spanned<Attribute_>` to a struct),
 - moves a `MetaItem`'s name from the `MetaItemKind` variants to a field of `MetaItem`,
 - avoids needlessly wrapping `ast::MetaItem` with `P`,
 - moves string interning into `syntax::symbol` (`ast::Name` is a reexport of `symbol::Symbol` for now),
 - replaces `InternedString` with `Symbol` in the AST, HIR, and various other places, and
 - refactors `ast::CrateConfig` from a `Vec` to a `HashSet`.

r? @eddyb

12 files changed, 76 insertions, 90 deletions

diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index d7bc2a6faee..d14b59d6c70 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -15,8 +15,8 @@ use syntax::ast::{self, Expr, Generics, ItemKind, MetaItem, VariantData};
 use syntax::attr;
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::{keywords, InternedString};
 use syntax::ptr::P;
+use syntax::symbol::{Symbol, keywords};
 use syntax_pos::Span;
 
 pub fn expand_deriving_clone(cx: &mut ExtCtxt,
@@ -74,7 +74,7 @@ pub fn expand_deriving_clone(cx: &mut ExtCtxt,
         _ => cx.span_bug(span, "#[derive(Clone)] on trait item or impl item"),
     }
 
-    let inline = cx.meta_word(span, InternedString::new("inline"));
+    let inline = cx.meta_word(span, Symbol::intern("inline"));
     let attrs = vec![cx.attribute(span, inline)];
     let trait_def = TraitDef {
         span: span,
diff --git a/src/libsyntax_ext/deriving/cmp/eq.rs b/src/libsyntax_ext/deriving/cmp/eq.rs
index fa0fb2492c5..6ab5987a159 100644
--- a/src/libsyntax_ext/deriving/cmp/eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/eq.rs
@@ -14,8 +14,8 @@ use deriving::generic::ty::*;
 use syntax::ast::{self, Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::InternedString;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_eq(cx: &mut ExtCtxt,
@@ -23,9 +23,9 @@ pub fn expand_deriving_eq(cx: &mut ExtCtxt,
                           mitem: &MetaItem,
                           item: &Annotatable,
                           push: &mut FnMut(Annotatable)) {
-    let inline = cx.meta_word(span, InternedString::new("inline"));
-    let hidden = cx.meta_list_item_word(span, InternedString::new("hidden"));
-    let doc = cx.meta_list(span, InternedString::new("doc"), vec![hidden]);
+    let inline = cx.meta_word(span, Symbol::intern("inline"));
+    let hidden = cx.meta_list_item_word(span, Symbol::intern("hidden"));
+    let doc = cx.meta_list(span, Symbol::intern("doc"), vec![hidden]);
     let attrs = vec![cx.attribute(span, inline), cx.attribute(span, doc)];
     let trait_def = TraitDef {
         span: span,
diff --git a/src/libsyntax_ext/deriving/cmp/ord.rs b/src/libsyntax_ext/deriving/cmp/ord.rs
index 6b2e36e63b6..9fc3d997585 100644
--- a/src/libsyntax_ext/deriving/cmp/ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/ord.rs
@@ -14,8 +14,8 @@ use deriving::generic::ty::*;
 use syntax::ast::{self, Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::InternedString;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_ord(cx: &mut ExtCtxt,
@@ -23,7 +23,7 @@ pub fn expand_deriving_ord(cx: &mut ExtCtxt,
                            mitem: &MetaItem,
                            item: &Annotatable,
                            push: &mut FnMut(Annotatable)) {
-    let inline = cx.meta_word(span, InternedString::new("inline"));
+    let inline = cx.meta_word(span, Symbol::intern("inline"));
     let attrs = vec![cx.attribute(span, inline)];
     let trait_def = TraitDef {
         span: span,
diff --git a/src/libsyntax_ext/deriving/cmp/partial_eq.rs b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
index c46d4b34173..f2a050ce971 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
@@ -14,8 +14,8 @@ use deriving::generic::ty::*;
 use syntax::ast::{BinOpKind, Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::InternedString;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt,
@@ -64,7 +64,7 @@ pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt,
 
     macro_rules! md {
         ($name:expr, $f:ident) => { {
-            let inline = cx.meta_word(span, InternedString::new("inline"));
+            let inline = cx.meta_word(span, Symbol::intern("inline"));
             let attrs = vec![cx.attribute(span, inline)];
             MethodDef {
                 name: $name,
diff --git a/src/libsyntax_ext/deriving/cmp/partial_ord.rs b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
index 597ff306b3d..ce4d549d696 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
@@ -16,8 +16,8 @@ use deriving::generic::ty::*;
 use syntax::ast::{self, BinOpKind, Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::InternedString;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
@@ -27,7 +27,7 @@ pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
                                    push: &mut FnMut(Annotatable)) {
     macro_rules! md {
         ($name:expr, $op:expr, $equal:expr) => { {
-            let inline = cx.meta_word(span, InternedString::new("inline"));
+            let inline = cx.meta_word(span, Symbol::intern("inline"));
             let attrs = vec![cx.attribute(span, inline)];
             MethodDef {
                 name: $name,
@@ -51,7 +51,7 @@ pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
                                     vec![Box::new(ordering_ty)],
                                     true));
 
-    let inline = cx.meta_word(span, InternedString::new("inline"));
+    let inline = cx.meta_word(span, Symbol::intern("inline"));
     let attrs = vec![cx.attribute(span, inline)];
 
     let partial_cmp_def = MethodDef {
diff --git a/src/libsyntax_ext/deriving/custom.rs b/src/libsyntax_ext/deriving/custom.rs
index e101757ad23..1076a6a6d63 100644
--- a/src/libsyntax_ext/deriving/custom.rs
+++ b/src/libsyntax_ext/deriving/custom.rs
@@ -17,10 +17,9 @@ use syntax::attr::{mark_used, mark_known};
 use syntax::codemap::Span;
 use syntax::ext::base::*;
 use syntax::fold::Folder;
-use syntax::parse::token::InternedString;
 use syntax::visit::Visitor;
 
-struct MarkAttrs<'a>(&'a [InternedString]);
+struct MarkAttrs<'a>(&'a [ast::Name]);
 
 impl<'a> Visitor for MarkAttrs<'a> {
     fn visit_attribute(&mut self, attr: &Attribute) {
@@ -33,13 +32,11 @@ impl<'a> Visitor for MarkAttrs<'a> {
 
 pub struct CustomDerive {
     inner: fn(TokenStream) -> TokenStream,
-    attrs: Vec<InternedString>,
+    attrs: Vec<ast::Name>,
 }
 
 impl CustomDerive {
-    pub fn new(inner: fn(TokenStream) -> TokenStream,
-               attrs: Vec<InternedString>)
-               -> CustomDerive {
+    pub fn new(inner: fn(TokenStream) -> TokenStream, attrs: Vec<ast::Name>) -> CustomDerive {
         CustomDerive { inner: inner, attrs: attrs }
     }
 }
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index f367fed9cc2..a767716466c 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -11,11 +11,10 @@
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
-use syntax::ast;
+use syntax::ast::{self, Ident};
 use syntax::ast::{Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token;
 use syntax::ptr::P;
 use syntax_pos::{DUMMY_SP, Span};
 
@@ -69,9 +68,8 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
 
     // We want to make sure we have the expn_id set so that we can use unstable methods
     let span = Span { expn_id: cx.backtrace(), ..span };
-    let name = cx.expr_lit(span,
-                           ast::LitKind::Str(ident.name.as_str(), ast::StrStyle::Cooked));
-    let builder = token::str_to_ident("builder");
+    let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
+    let builder = Ident::from_str("builder");
     let builder_expr = cx.expr_ident(span, builder.clone());
 
     let fmt = substr.nonself_args[0].clone();
@@ -83,7 +81,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
             if !is_struct {
                 // tuple struct/"normal" variant
                 let expr =
-                    cx.expr_method_call(span, fmt, token::str_to_ident("debug_tuple"), vec![name]);
+                    cx.expr_method_call(span, fmt, Ident::from_str("debug_tuple"), vec![name]);
                 stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
 
                 for field in fields {
@@ -93,7 +91,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
 
                     let expr = cx.expr_method_call(span,
                                                    builder_expr.clone(),
-                                                   token::str_to_ident("field"),
+                                                   Ident::from_str("field"),
                                                    vec![field]);
 
                     // Use `let _ = expr;` to avoid triggering the
@@ -103,12 +101,12 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
             } else {
                 // normal struct/struct variant
                 let expr =
-                    cx.expr_method_call(span, fmt, token::str_to_ident("debug_struct"), vec![name]);
+                    cx.expr_method_call(span, fmt, Ident::from_str("debug_struct"), vec![name]);
                 stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
 
                 for field in fields {
                     let name = cx.expr_lit(field.span,
-                                           ast::LitKind::Str(field.name.unwrap().name.as_str(),
+                                           ast::LitKind::Str(field.name.unwrap().name,
                                                              ast::StrStyle::Cooked));
 
                     // Use double indirection to make sure this works for unsized types
@@ -116,7 +114,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
                     let field = cx.expr_addr_of(field.span, field);
                     let expr = cx.expr_method_call(span,
                                                    builder_expr.clone(),
-                                                   token::str_to_ident("field"),
+                                                   Ident::from_str("field"),
                                                    vec![name, field]);
                     stmts.push(stmt_let_undescore(cx, span, expr));
                 }
@@ -126,7 +124,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
         _ => unreachable!(),
     };
 
-    let expr = cx.expr_method_call(span, builder_expr, token::str_to_ident("finish"), vec![]);
+    let expr = cx.expr_method_call(span, builder_expr, Ident::from_str("finish"), vec![]);
 
     stmts.push(cx.stmt_expr(expr));
     let block = cx.block(span, stmts);
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index dc1f7b4e620..e2634c60dca 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -18,9 +18,8 @@ use syntax::ast;
 use syntax::ast::{Expr, MetaItem, Mutability};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::InternedString;
-use syntax::parse::token;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_rustc_decodable(cx: &mut ExtCtxt,
@@ -131,7 +130,7 @@ fn decodable_substructure(cx: &mut ExtCtxt,
             cx.expr_method_call(trait_span,
                                 decoder,
                                 cx.ident_of("read_struct"),
-                                vec![cx.expr_str(trait_span, substr.type_ident.name.as_str()),
+                                vec![cx.expr_str(trait_span, substr.type_ident.name),
                                      cx.expr_usize(trait_span, nfields),
                                      cx.lambda1(trait_span, result, blkarg)])
         }
@@ -143,7 +142,7 @@ fn decodable_substructure(cx: &mut ExtCtxt,
             let rvariant_arg = cx.ident_of("read_enum_variant_arg");
 
             for (i, &(ident, v_span, ref parts)) in fields.iter().enumerate() {
-                variants.push(cx.expr_str(v_span, ident.name.as_str()));
+                variants.push(cx.expr_str(v_span, ident.name));
 
                 let path = cx.path(trait_span, vec![substr.type_ident, ident]);
                 let decoded = decode_static_fields(cx, v_span, path, parts, |cx, span, _, field| {
@@ -175,7 +174,7 @@ fn decodable_substructure(cx: &mut ExtCtxt,
             cx.expr_method_call(trait_span,
                                 decoder,
                                 cx.ident_of("read_enum"),
-                                vec![cx.expr_str(trait_span, substr.type_ident.name.as_str()),
+                                vec![cx.expr_str(trait_span, substr.type_ident.name),
                                      cx.lambda1(trait_span, result, blkarg)])
         }
         _ => cx.bug("expected StaticEnum or StaticStruct in derive(Decodable)"),
@@ -191,7 +190,7 @@ fn decode_static_fields<F>(cx: &mut ExtCtxt,
                            fields: &StaticFields,
                            mut getarg: F)
                            -> P<Expr>
-    where F: FnMut(&mut ExtCtxt, Span, InternedString, usize) -> P<Expr>
+    where F: FnMut(&mut ExtCtxt, Span, Symbol, usize) -> P<Expr>
 {
     match *fields {
         Unnamed(ref fields, is_tuple) => {
@@ -202,10 +201,7 @@ fn decode_static_fields<F>(cx: &mut ExtCtxt,
                 let fields = fields.iter()
                     .enumerate()
                     .map(|(i, &span)| {
-                        getarg(cx,
-                               span,
-                               token::intern_and_get_ident(&format!("_field{}", i)),
-                               i)
+                        getarg(cx, span, Symbol::intern(&format!("_field{}", i)), i)
                     })
                     .collect();
 
@@ -217,7 +213,7 @@ fn decode_static_fields<F>(cx: &mut ExtCtxt,
             let fields = fields.iter()
                 .enumerate()
                 .map(|(i, &(ident, span))| {
-                    let arg = getarg(cx, span, ident.name.as_str(), i);
+                    let arg = getarg(cx, span, ident.name, i);
                     cx.field_imm(span, ident, arg)
                 })
                 .collect();
diff --git a/src/libsyntax_ext/deriving/default.rs b/src/libsyntax_ext/deriving/default.rs
index b15fd2b49a6..69391f48c22 100644
--- a/src/libsyntax_ext/deriving/default.rs
+++ b/src/libsyntax_ext/deriving/default.rs
@@ -14,8 +14,8 @@ use deriving::generic::ty::*;
 use syntax::ast::{Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token::InternedString;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_default(cx: &mut ExtCtxt,
@@ -23,7 +23,7 @@ pub fn expand_deriving_default(cx: &mut ExtCtxt,
                                mitem: &MetaItem,
                                item: &Annotatable,
                                push: &mut FnMut(Annotatable)) {
-    let inline = cx.meta_word(span, InternedString::new("inline"));
+    let inline = cx.meta_word(span, Symbol::intern("inline"));
     let attrs = vec![cx.attribute(span, inline)];
     let trait_def = TraitDef {
         span: span,
diff --git a/src/libsyntax_ext/deriving/encodable.rs b/src/libsyntax_ext/deriving/encodable.rs
index ebbddc6e480..092738ab8a0 100644
--- a/src/libsyntax_ext/deriving/encodable.rs
+++ b/src/libsyntax_ext/deriving/encodable.rs
@@ -95,8 +95,8 @@ use deriving::generic::ty::*;
 use syntax::ast::{Expr, ExprKind, MetaItem, Mutability};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
-use syntax::parse::token;
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 pub fn expand_deriving_rustc_encodable(cx: &mut ExtCtxt,
@@ -192,8 +192,8 @@ fn encodable_substructure(cx: &mut ExtCtxt,
             let mut stmts = Vec::new();
             for (i, &FieldInfo { name, ref self_, span, .. }) in fields.iter().enumerate() {
                 let name = match name {
-                    Some(id) => id.name.as_str(),
-                    None => token::intern_and_get_ident(&format!("_field{}", i)),
+                    Some(id) => id.name,
+                    None => Symbol::intern(&format!("_field{}", i)),
                 };
                 let self_ref = cx.expr_addr_of(span, self_.clone());
                 let enc = cx.expr_call(span, fn_path.clone(), vec![self_ref, blkencoder.clone()]);
@@ -226,7 +226,7 @@ fn encodable_substructure(cx: &mut ExtCtxt,
             cx.expr_method_call(trait_span,
                                 encoder,
                                 cx.ident_of("emit_struct"),
-                                vec![cx.expr_str(trait_span, substr.type_ident.name.as_str()),
+                                vec![cx.expr_str(trait_span, substr.type_ident.name),
                                      cx.expr_usize(trait_span, fields.len()),
                                      blk])
         }
@@ -265,7 +265,7 @@ fn encodable_substructure(cx: &mut ExtCtxt,
             }
 
             let blk = cx.lambda_stmts_1(trait_span, stmts, blkarg);
-            let name = cx.expr_str(trait_span, variant.node.name.name.as_str());
+            let name = cx.expr_str(trait_span, variant.node.name.name);
             let call = cx.expr_method_call(trait_span,
                                            blkencoder,
                                            cx.ident_of("emit_enum_variant"),
@@ -277,8 +277,7 @@ fn encodable_substructure(cx: &mut ExtCtxt,
             let ret = cx.expr_method_call(trait_span,
                                           encoder,
                                           cx.ident_of("emit_enum"),
-                                          vec![cx.expr_str(trait_span,
-                                                           substr.type_ident.name.as_str()),
+                                          vec![cx.expr_str(trait_span ,substr.type_ident.name),
                                                blk]);
             cx.expr_block(cx.block(trait_span, vec![me, cx.stmt_expr(ret)]))
         }
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index e6b63be3efc..63cd7678321 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -198,8 +198,8 @@ use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
 use syntax::codemap::{self, dummy_spanned, respan};
 use syntax::util::move_map::MoveMap;
-use syntax::parse::token::{InternedString, keywords};
 use syntax::ptr::P;
+use syntax::symbol::{Symbol, keywords};
 use syntax_pos::{DUMMY_SP, Span};
 use errors::Handler;
 
@@ -442,7 +442,7 @@ impl<'a> TraitDef<'a> {
                 attrs.extend(item.attrs
                     .iter()
                     .filter(|a| {
-                        match &a.name()[..] {
+                        match &*a.name().as_str() {
                             "allow" | "warn" | "deny" | "forbid" | "stable" | "unstable" => true,
                             _ => false,
                         }
@@ -639,15 +639,15 @@ impl<'a> TraitDef<'a> {
 
         let attr = cx.attribute(self.span,
                                 cx.meta_word(self.span,
-                                             InternedString::new("automatically_derived")));
+                                             Symbol::intern("automatically_derived")));
         // Just mark it now since we know that it'll end up used downstream
         attr::mark_used(&attr);
         let opt_trait_ref = Some(trait_ref);
-        let unused_qual = cx.attribute(self.span,
-                                       cx.meta_list(self.span,
-                                                    InternedString::new("allow"),
-                                                    vec![cx.meta_list_item_word(self.span,
-                                           InternedString::new("unused_qualifications"))]));
+        let unused_qual = {
+            let word = cx.meta_list_item_word(self.span, Symbol::intern("unused_qualifications"));
+            cx.attribute(self.span, cx.meta_list(self.span, Symbol::intern("allow"), vec![word]))
+        };
+
         let mut a = vec![attr, unused_qual];
         a.extend(self.attributes.iter().cloned());
 
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index b1d473820f7..535d7de19e3 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -16,8 +16,8 @@ use syntax::codemap;
 use syntax::ext::base::{Annotatable, ExtCtxt, SyntaxExtension};
 use syntax::ext::build::AstBuilder;
 use syntax::feature_gate::{self, emit_feature_err};
-use syntax::parse::token::{intern, intern_and_get_ident};
 use syntax::ptr::P;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
 macro_rules! pathvec {
@@ -80,7 +80,7 @@ fn allow_unstable(cx: &mut ExtCtxt, span: Span, attr_name: &str) -> Span {
         expn_id: cx.codemap().record_expansion(codemap::ExpnInfo {
             call_site: span,
             callee: codemap::NameAndSpan {
-                format: codemap::MacroAttribute(intern(attr_name)),
+                format: codemap::MacroAttribute(Symbol::intern(attr_name)),
                 span: Some(span),
                 allow_internal_unstable: true,
             },
@@ -105,9 +105,10 @@ pub fn expand_derive(cx: &mut ExtCtxt,
         }
     };
 
+    let derive = Symbol::intern("derive");
     let mut derive_attrs = Vec::new();
     item = item.map_attrs(|attrs| {
-        let partition = attrs.into_iter().partition(|attr| &attr.name() == "derive");
+        let partition = attrs.into_iter().partition(|attr| attr.name() == derive);
         derive_attrs = partition.0;
         partition.1
     });
@@ -115,7 +116,7 @@ pub fn expand_derive(cx: &mut ExtCtxt,
     // Expand `#[derive]`s after other attribute macro invocations.
     if cx.resolver.find_attr_invoc(&mut item.attrs.clone()).is_some() {
         return vec![Annotatable::Item(item.map_attrs(|mut attrs| {
-            attrs.push(cx.attribute(span, P(mitem.clone())));
+            attrs.push(cx.attribute(span, mitem.clone()));
             attrs.extend(derive_attrs);
             attrs
         }))];
@@ -135,7 +136,7 @@ pub fn expand_derive(cx: &mut ExtCtxt,
 
     let mut traits = get_traits(mitem, cx);
     for derive_attr in derive_attrs {
-        traits.extend(get_traits(&derive_attr.node.value, cx));
+        traits.extend(get_traits(&derive_attr.value, cx));
     }
 
     // First, weed out malformed #[derive]
@@ -158,9 +159,8 @@ pub fn expand_derive(cx: &mut ExtCtxt,
         let tword = titem.word().unwrap();
         let tname = tword.name();
 
-        if is_builtin_trait(&tname) || {
-            let derive_mode =
-                ast::Path::from_ident(titem.span, ast::Ident::with_empty_ctxt(intern(&tname)));
+        if is_builtin_trait(tname) || {
+            let derive_mode = ast::Path::from_ident(titem.span, ast::Ident::with_empty_ctxt(tname));
             cx.resolver.resolve_macro(cx.current_expansion.mark, &derive_mode, false).map(|ext| {
                 if let SyntaxExtension::CustomDerive(_) = *ext { true } else { false }
             }).unwrap_or(false)
@@ -176,7 +176,7 @@ pub fn expand_derive(cx: &mut ExtCtxt,
                                            feature_gate::EXPLAIN_CUSTOM_DERIVE);
         } else {
             cx.span_warn(titem.span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
-            let name = intern_and_get_ident(&format!("derive_{}", tname));
+            let name = Symbol::intern(&format!("derive_{}", tname));
             let mitem = cx.meta_word(titem.span, name);
             new_attributes.push(cx.attribute(mitem.span, mitem));
         }
@@ -186,9 +186,7 @@ pub fn expand_derive(cx: &mut ExtCtxt,
         item = item.map(|mut i| {
             i.attrs.extend(new_attributes);
             if traits.len() > 0 {
-                let list = cx.meta_list(mitem.span,
-                                        intern_and_get_ident("derive"),
-                                        traits);
+                let list = cx.meta_list(mitem.span, derive, traits);
                 i.attrs.push(cx.attribute(mitem.span, list));
             }
             i
@@ -217,7 +215,7 @@ pub fn expand_derive(cx: &mut ExtCtxt,
     let macros_11_derive = traits.iter()
                                  .cloned()
                                  .enumerate()
-                                 .filter(|&(_, ref name)| !is_builtin_trait(&name.name().unwrap()))
+                                 .filter(|&(_, ref name)| !is_builtin_trait(name.name().unwrap()))
                                  .next();
     if let Some((i, titem)) = macros_11_derive {
         if !cx.ecfg.features.unwrap().proc_macro {
@@ -226,24 +224,20 @@ pub fn expand_derive(cx: &mut ExtCtxt,
             emit_feature_err(cx.parse_sess, "proc_macro", titem.span, issue, msg);
         }
 
-        let tname = ast::Ident::with_empty_ctxt(intern(&titem.name().unwrap()));
+        let tname = ast::Ident::with_empty_ctxt(titem.name().unwrap());
         let path = ast::Path::from_ident(titem.span, tname);
         let ext = cx.resolver.resolve_macro(cx.current_expansion.mark, &path, false).unwrap();
 
         traits.remove(i);
         if traits.len() > 0 {
             item = item.map(|mut i| {
-                let list = cx.meta_list(mitem.span,
-                                        intern_and_get_ident("derive"),
-                                        traits);
+                let list = cx.meta_list(mitem.span, derive, traits);
                 i.attrs.push(cx.attribute(mitem.span, list));
                 i
             });
         }
         let titem = cx.meta_list_item_word(titem.span, titem.name().unwrap());
-        let mitem = cx.meta_list(titem.span,
-                                 intern_and_get_ident("derive"),
-                                 vec![titem]);
+        let mitem = cx.meta_list(titem.span, derive, vec![titem]);
         let item = Annotatable::Item(item);
         if let SyntaxExtension::CustomDerive(ref ext) = *ext {
             return ext.expand(cx, mitem.span, &mitem, item);
@@ -257,9 +251,10 @@ pub fn expand_derive(cx: &mut ExtCtxt,
 
     // RFC #1445. `#[derive(PartialEq, Eq)]` adds a (trusted)
     // `#[structural_match]` attribute.
-    if traits.iter().filter_map(|t| t.name()).any(|t| t == "PartialEq") &&
-       traits.iter().filter_map(|t| t.name()).any(|t| t == "Eq") {
-        let structural_match = intern_and_get_ident("structural_match");
+    let (partial_eq, eq) = (Symbol::intern("PartialEq"), Symbol::intern("Eq"));
+    if traits.iter().any(|t| t.name() == Some(partial_eq)) &&
+       traits.iter().any(|t| t.name() == Some(eq)) {
+        let structural_match = Symbol::intern("structural_match");
         let span = allow_unstable(cx, span, "derive(PartialEq, Eq)");
         let meta = cx.meta_word(span, structural_match);
         item = item.map(|mut i| {
@@ -272,9 +267,10 @@ pub fn expand_derive(cx: &mut ExtCtxt,
     // the same as the copy implementation.
     //
     // Add a marker attribute here picked up during #[derive(Clone)]
-    if traits.iter().filter_map(|t| t.name()).any(|t| t == "Clone") &&
-       traits.iter().filter_map(|t| t.name()).any(|t| t == "Copy") {
-        let marker = intern_and_get_ident("rustc_copy_clone_marker");
+    let (copy, clone) = (Symbol::intern("Copy"), Symbol::intern("Clone"));
+    if traits.iter().any(|t| t.name() == Some(clone)) &&
+       traits.iter().any(|t| t.name() == Some(copy)) {
+        let marker = Symbol::intern("rustc_copy_clone_marker");
         let span = allow_unstable(cx, span, "derive(Copy, Clone)");
         let meta = cx.meta_word(span, marker);
         item = item.map(|mut i| {
@@ -286,14 +282,14 @@ pub fn expand_derive(cx: &mut ExtCtxt,
     let mut items = Vec::new();
     for titem in traits.iter() {
         let tname = titem.word().unwrap().name();
-        let name = intern_and_get_ident(&format!("derive({})", tname));
+        let name = Symbol::intern(&format!("derive({})", tname));
         let mitem = cx.meta_word(titem.span, name);
 
         let span = Span {
             expn_id: cx.codemap().record_expansion(codemap::ExpnInfo {
                 call_site: titem.span,
                 callee: codemap::NameAndSpan {
-                    format: codemap::MacroAttribute(intern(&format!("derive({})", tname))),
+                    format: codemap::MacroAttribute(Symbol::intern(&format!("derive({})", tname))),
                     span: Some(titem.span),
                     allow_internal_unstable: true,
                 },
@@ -302,7 +298,7 @@ pub fn expand_derive(cx: &mut ExtCtxt,
         };
 
         let my_item = Annotatable::Item(item);
-        expand_builtin(&tname, cx, span, &mitem, &my_item, &mut |a| {
+        expand_builtin(&tname.as_str(), cx, span, &mitem, &my_item, &mut |a| {
             items.push(a);
         });
         item = my_item.expect_item();
@@ -314,8 +310,8 @@ pub fn expand_derive(cx: &mut ExtCtxt,
 
 macro_rules! derive_traits {
     ($( $name:expr => $func:path, )+) => {
-        pub fn is_builtin_trait(name: &str) -> bool {
-            match name {
+        pub fn is_builtin_trait(name: ast::Name) -> bool {
+            match &*name.as_str() {
                 $( $name )|+ => true,
                 _ => false,
             }
@@ -412,7 +408,7 @@ fn call_intrinsic(cx: &ExtCtxt,
     span.expn_id = cx.codemap().record_expansion(codemap::ExpnInfo {
         call_site: span,
         callee: codemap::NameAndSpan {
-            format: codemap::MacroAttribute(intern("derive")),
+            format: codemap::MacroAttribute(Symbol::intern("derive")),
             span: Some(span),
             allow_internal_unstable: true,
         },