Implement new inference algorithm.

src/rustc/metadata/astencode.rs

@@ -634,6 +634,7 @@ impl helpers for @e::encode_ctxt {
     fn ty_str_ctxt() -> @tyencode::ctxt {
         @{ds: e::def_to_str,
           tcx: self.ccx.tcx,
+          reachable: self.ccx.reachable,
           abbrevs: tyencode::ac_use_abbrevs(self.type_abbrevs)}
     }
 }