Remove `LazyTokenStream`.

It's present within `Token::Interpolated` as an optimization, so that if
a nonterminal is converted to a `TokenStream` multiple times, the
first-computed value is saved and reused.

But in practice it's not needed. `interpolated_to_tokenstream()` is a
cold function: it's only called a few dozen times while compiling rustc
itself, and a few hundred times across the entire `rustc-perf` suite.
Furthermore, when it is called, it is almost always the first
conversion, so no benefit is gained from it.

So this commit removes `LazyTokenStream`, along with the now-unnecessary
`Token::interpolated()`.

As well as a significant simplification, the removal speeds things up
slightly, mostly due to not having to `drop` the `LazyTokenStream`
instances.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 0e48e3a5dff..dcf9815f6d1 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -257,7 +257,7 @@ pub fn token_to_string(tok: &Token) -> String {
         token::Comment              => "/* */".to_string(),
         token::Shebang(s)           => format!("/* shebang: {}*/", s),
 
-        token::Interpolated(ref nt) => nonterminal_to_string(&nt.0),
+        token::Interpolated(ref nt) => nonterminal_to_string(nt),
     }
 }