treestate: Allow serializing dynamically sized value

Summary: Used in {D99974194} to implement serialize for `[u8]`.

Reviewed By: diliop

Differential Revision: D100345293

fbshipit-source-id: 4b96ef48e65f2aa0c45c5f394efa9304edfe9ffb

Author: David Tolnay

eden/scm/lib/treestate/src/serialization.rs

@@ -42,15 +42,14 @@ use crate::tree::Node;
 use crate::tree::NodeEntry;
 use crate::tree::NodeEntryMap;
 
-pub trait Serializable
-where
-    Self: Sized,
-{
+pub trait Serializable {
     /// Serialize the storable data to a `Write` stream.
     fn serialize(&self, w: &mut dyn Write) -> Result<()>;
 
     /// Deserialize a new data item from a `Read` stream.
-    fn deserialize(r: &mut dyn Read) -> Result<Self>;
+    fn deserialize(r: &mut dyn Read) -> Result<Self>
+    where
+        Self: Sized;
 }
 
 impl Serializable for FileState {