Avoid unnecessary internings.

Most involving `Symbol::intern` on string literals.

6 files changed, 11 insertions, 20 deletions

diff --git a/src/libsyntax/ext/derive.rs b/src/libsyntax/ext/derive.rs
index 6e789c4c708..c47224ca0ce 100644
--- a/src/libsyntax/ext/derive.rs
+++ b/src/libsyntax/ext/derive.rs
@@ -58,10 +58,7 @@ pub fn add_derived_markers<T>(cx: &mut ExtCtxt<'_>, span: Span, traits: &[ast::P
         call_site: span,
         def_site: None,
         format: ExpnFormat::MacroAttribute(Symbol::intern(&pretty_name)),
-        allow_internal_unstable: Some(vec![
-            Symbol::intern("rustc_attrs"),
-            Symbol::intern("structural_match"),
-        ].into()),
+        allow_internal_unstable: Some(vec![sym::rustc_attrs, sym::structural_match].into()),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: cx.parse_sess.edition,
@@ -74,7 +71,7 @@ pub fn add_derived_markers<T>(cx: &mut ExtCtxt<'_>, span: Span, traits: &[ast::P
             attrs.push(cx.attribute(span, meta));
         }
         if names.contains(&Symbol::intern("Copy")) {
-            let meta = cx.meta_word(span, Symbol::intern("rustc_copy_clone_marker"));
+            let meta = cx.meta_word(span, sym::rustc_copy_clone_marker);
             attrs.push(cx.attribute(span, meta));
         }
     });
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index fbe052252a1..c2a73b662c6 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -938,7 +938,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             }
             BuiltinDerive(func) => {
                 expn_info.allow_internal_unstable = Some(vec![
-                    Symbol::intern("rustc_attrs"),
+                    sym::rustc_attrs,
                     Symbol::intern("derive_clone_copy"),
                     Symbol::intern("derive_eq"),
                     Symbol::intern("libstd_sys_internals"), // RustcDeserialize and RustcSerialize
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 2debd8f048b..285c88357a6 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -396,7 +396,7 @@ pub fn compile(
                         future this will become a hard error. Please use `allow_internal_unstable(\
                         foo, bar)` to only allow the `foo` and `bar` features",
                     );
-                    vec![Symbol::intern("allow_internal_unstable_backcompat_hack")].into()
+                    vec![sym::allow_internal_unstable_backcompat_hack].into()
                 })
             );
         let allow_internal_unsafe = attr::contains_name(&def.attrs, sym::allow_internal_unsafe);
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 6c29437362c..e0430ac5563 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -5787,7 +5787,7 @@ impl<'a> Parser<'a> {
             VisibilityKind::Inherited => {}
             _ => {
                 let is_macro_rules: bool = match self.token {
-                    token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
+                    token::Ident(sid, _) => sid.name == sym::macro_rules,
                     _ => false,
                 };
                 let mut err = if is_macro_rules {
diff --git a/src/libsyntax/std_inject.rs b/src/libsyntax/std_inject.rs
index 398705857bb..eea94f0d194 100644
--- a/src/libsyntax/std_inject.rs
+++ b/src/libsyntax/std_inject.rs
@@ -20,9 +20,7 @@ fn ignored_span(sp: Span, edition: Edition) -> Span {
         call_site: DUMMY_SP,
         def_site: None,
         format: MacroAttribute(Symbol::intern("std_inject")),
-        allow_internal_unstable: Some(vec![
-            Symbol::intern("prelude_import"),
-        ].into()),
+        allow_internal_unstable: Some(vec![sym::prelude_import].into()),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition,
@@ -98,7 +96,7 @@ pub fn maybe_inject_crates_ref(
     krate.module.items.insert(0, P(ast::Item {
         attrs: vec![ast::Attribute {
             style: ast::AttrStyle::Outer,
-            path: ast::Path::from_ident(ast::Ident::new(Symbol::intern("prelude_import"), span)),
+            path: ast::Path::from_ident(ast::Ident::new(sym::prelude_import, span)),
             tokens: TokenStream::empty(),
             id: attr::mk_attr_id(),
             is_sugared_doc: false,
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index d1e11da4e7c..1998ec19f13 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -283,12 +283,8 @@ fn generate_test_harness(sess: &ParseSess,
     mark.set_expn_info(ExpnInfo {
         call_site: DUMMY_SP,
         def_site: None,
-        format: MacroAttribute(Symbol::intern("test_case")),
-        allow_internal_unstable: Some(vec![
-            Symbol::intern("main"),
-            Symbol::intern("test"),
-            Symbol::intern("rustc_attrs"),
-        ].into()),
+        format: MacroAttribute(sym::test_case),
+        allow_internal_unstable: Some(vec![sym::main, sym::test, sym::rustc_attrs].into()),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: sess.edition,
@@ -347,14 +343,14 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     let call_test_main = ecx.stmt_expr(call_test_main);
 
     // #![main]
-    let main_meta = ecx.meta_word(sp, Symbol::intern("main"));
+    let main_meta = ecx.meta_word(sp, sym::main);
     let main_attr = ecx.attribute(sp, main_meta);
 
     // extern crate test as test_gensym
     let test_extern_stmt = ecx.stmt_item(sp, ecx.item(sp,
         test_id,
         vec![],
-        ast::ItemKind::ExternCrate(Some(Symbol::intern("test")))
+        ast::ItemKind::ExternCrate(Some(sym::test))
     ));
 
     // pub fn main() { ... }