don't normalize in astconv

We delay projection normalization to further stages in order to
register user type annotations before normalization in HIR typeck.

There are two consumers of astconv: ItemCtxt and FnCtxt.
The former already expects unnormalized types from astconv, see its
AstConv trait impl.
The latter needs `RawTy` for a cleaner interface.

Unfortunately astconv still needs the normalization machinery in
order to resolve enum variants that have projections in the self type,
e.g. `<<T as Trait>::Assoc>::StructVariant {}`.
This is why `AstConv::normalize_ty_2` is necessary.

compiler/rustc_traits/src/type_op.rs

@@ -91,6 +91,7 @@ pub fn type_op_ascribe_user_type_with_span<'tcx>(
     }
 
     if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
+        let self_ty = ocx.normalize(&cause, param_env, self_ty);
         let impl_self_ty = tcx.bound_type_of(impl_def_id).subst(tcx, substs);
         let impl_self_ty = ocx.normalize(&cause, param_env, impl_self_ty);