make UnixFSHAMTShard implement the ADL interface (#11)

* make UnixFSHAMTShard implement the ADL interface
* add checks that UnixFSBasicDir and PathedPBNode implement the ADL interface

Author: aschmahmann

Diff for: directory/basicdir.go

@@ -13,6 +13,7 @@ import (
 
 var _ ipld.Node = UnixFSBasicDir(nil)
 var _ schema.TypedNode = UnixFSBasicDir(nil)
+var _ ipld.ADL = UnixFSBasicDir(nil)
 
 type UnixFSBasicDir = *_UnixFSBasicDir
 

Diff for: hamt/shardeddir.go

@@ -19,6 +19,7 @@ const (
 
 var _ ipld.Node = UnixFSHAMTShard(nil)
 var _ schema.TypedNode = UnixFSHAMTShard(nil)
+var _ ipld.ADL = UnixFSHAMTShard(nil)
 
 // UnixFSHAMTShared is an IPLD Prime Node that provides a read interface
 // to a UnixFS HAMT
@@ -53,6 +54,10 @@ func NewUnixFSHAMTShard(ctx context.Context, substrate dagpb.PBNode, data data.U
 	}, nil
 }
 
+func (n UnixFSHAMTShard) Substrate() ipld.Node {
+	return n._substrate
+}
+
 func (n UnixFSHAMTShard) Kind() ipld.Kind {
 	return n._substrate.Kind()
 }

Diff for: pathpbnode.go

@@ -10,6 +10,7 @@ import (
 
 var _ ipld.Node = PathedPBNode(nil)
 var _ schema.TypedNode = PathedPBNode(nil)
+var _ ipld.ADL = PathedPBNode(nil)
 
 type PathedPBNode = *_PathedPBNode