Resolve type_repetition_in_bounds clippy lint

    error: this type has already been used as a bound predicate
       --> src/main.rs:311:5
        |
    311 |     T: rustc_serialize::Encodable,
        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = note: `-D clippy::type-repetition-in-bounds` implied by `-D clippy::pedantic`
        = help: consider combining the bounds: `T: Sized + rustc_serialize::Encodable`
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

Author: dtolnay

src/main.rs

@@ -302,13 +302,13 @@ where
     feature = "lib-rustc-serialize",
     any(feature = "stringify-dom", feature = "stringify-struct")
 ))]
-fn rustc_serialize_stringify<W, T: ?Sized>(
+fn rustc_serialize_stringify<W, T>(
     writer: W,
     value: &T,
 ) -> rustc_serialize::json::EncodeResult<()>
 where
     W: Write,
-    T: rustc_serialize::Encodable,
+    T: ?Sized + rustc_serialize::Encodable,
 {
     let mut writer = adapter::IoWriteAsFmtWrite::new(writer);
     let mut encoder = rustc_serialize::json::Encoder::new(&mut writer);