eddyb's changes for DST coercions

+ lots of rebasing

src/librustc/metadata/common.rs

@@ -259,3 +259,5 @@ pub const tag_codemap_filemap: usize = 0xa2;
 pub const tag_item_super_predicates: usize = 0xa3;
 
 pub const tag_defaulted_trait: usize = 0xa4;
+
+pub const tag_impl_coerce_unsized_kind: usize = 0xa5;

src/librustc/metadata/csearch.rs

@@ -279,6 +279,14 @@ pub fn get_impl_polarity<'tcx>(tcx: &ty::ctxt<'tcx>,
     decoder::get_impl_polarity(&*cdata, def.node)
 }
 
+pub fn get_custom_coerce_unsized_kind<'tcx>(tcx: &ty::ctxt<'tcx>,
+                                            def: ast::DefId)
+                                            -> Option<ty::CustomCoerceUnsized> {
+    let cstore = &tcx.sess.cstore;
+    let cdata = cstore.get_crate_data(def.krate);
+    decoder::get_custom_coerce_unsized_kind(&*cdata, def.node)
+}
+
 // Given a def_id for an impl, return the trait it implements,
 // if there is one.
 pub fn get_impl_trait<'tcx>(tcx: &ty::ctxt<'tcx>,

src/librustc/metadata/decoder.rs

@@ -489,6 +489,16 @@ pub fn get_impl_polarity<'tcx>(cdata: Cmd,
     }
 }
 
+pub fn get_custom_coerce_unsized_kind<'tcx>(cdata: Cmd,
+                                            id: ast::NodeId)
+                                            -> Option<ty::CustomCoerceUnsized> {
+    let item_doc = lookup_item(id, cdata.data());
+    reader::maybe_get_doc(item_doc, tag_impl_coerce_unsized_kind).map(|kind_doc| {
+        let mut decoder = reader::Decoder::new(kind_doc);
+        Decodable::decode(&mut decoder).unwrap()
+    })
+}
+
 pub fn get_impl_trait<'tcx>(cdata: Cmd,
                             id: ast::NodeId,
                             tcx: &ty::ctxt<'tcx>)

src/librustc/metadata/encoder.rs

@@ -1219,6 +1219,16 @@ fn encode_info_for_item(ecx: &EncodeContext,
         encode_attributes(rbml_w, &item.attrs);
         encode_unsafety(rbml_w, unsafety);
         encode_polarity(rbml_w, polarity);
+
+        match tcx.custom_coerce_unsized_kinds.borrow().get(&local_def(item.id)) {
+            Some(&kind) => {
+                rbml_w.start_tag(tag_impl_coerce_unsized_kind);
+                kind.encode(rbml_w);
+                rbml_w.end_tag();
+            }
+            None => {}
+        }
+
         match ty.node {
             ast::TyPath(None, ref path) if path.segments.len() == 1 => {
                 let name = path.segments.last().unwrap().identifier.name;