visitor-oriented fmt

this makes a decode+format benchmark drop from 75s to 14s...

(decode is 5s)

1 files changed, 2 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 3afdd60..8e0c4a5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -48,6 +48,8 @@
 #![no_std]
 #![deny(missing_docs)]
 
+#[cfg(feature="alloc")]
+extern crate alloc;
 #[cfg(feature="use-serde")]
 #[macro_use] extern crate serde_derive;
 #[cfg(feature="use-serde")]