Remove the `Option` in `TokenStream`.

It means an allocation is required to create an empty `TokenStream`, but
all other operations are simpler and marginally faster due to not having
to check for `None`. Overall it simplifies the code for a negligible
performance effect.

The commit also removes `TokenStream::empty` by implementing `Default`,
which is now possible.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsyntax/attr/mod.rs b/src/libsyntax/attr/mod.rs
index 7bef693a5be..c2c883fd20e 100644
--- a/src/libsyntax/attr/mod.rs
+++ b/src/libsyntax/attr/mod.rs
@@ -551,7 +551,7 @@ impl MetaItem {
 impl MetaItemKind {
     pub fn tokens(&self, span: Span) -> TokenStream {
         match *self {
-            MetaItemKind::Word => TokenStream::empty(),
+            MetaItemKind::Word => TokenStream::default(),
             MetaItemKind::NameValue(ref lit) => {
                 let mut vec = vec![TokenTree::token(token::Eq, span).into()];
                 lit.tokens().append_to_tree_and_joint_vec(&mut vec);