library/compiler: add `PointeeSized` bounds

As core uses an extern type (`ptr::VTable`), the default `?Sized` to
`MetaSized` migration isn't sufficient, and some code that previously
accepted `VTable` needs relaxed to continue to accept extern types.

Similarly, the compiler uses many extern types in `rustc_codegen_llvm`
and in the `rustc_middle::ty::List` implementation (`OpaqueListContents`)
some bounds must be relaxed to continue to accept these types.

Unfortunately, due to the current inability to relax `Deref::Target`,
some of the bounds in the standard library are forced to be stricter than
they ideally would be.

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
index 1eefd76f92b..8940d10696d 100644
--- a/compiler/rustc_serialize/src/serialize.rs
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -142,7 +142,7 @@ pub trait Decoder {
 ///   `rustc_metadata::rmeta::Lazy`.
 /// * `TyEncodable` should be used for types that are only serialized in crate
 ///   metadata or the incremental cache. This is most types in `rustc_middle`.
-pub trait Encodable<S: Encoder> {
+pub trait Encodable<S: Encoder>: crate::PointeeSized {
     fn encode(&self, s: &mut S);
 }
 
@@ -198,7 +198,7 @@ direct_serialize_impls! {
     char emit_char read_char
 }
 
-impl<S: Encoder, T: ?Sized> Encodable<S> for &T
+impl<S: Encoder, T: ?Sized + crate::PointeeSized> Encodable<S> for &T
 where
     T: Encodable<S>,
 {