rustc: Instantiate trait refs for automatically-derived implementations. Should fix check-fast. rs=bustage

Author: pcwalton

src/rustc/metadata/encoder.rs

@@ -556,6 +556,9 @@ fn encode_info_for_item(ecx: @encode_ctxt, ebml_w: ebml::Serializer,
     }
     let add_to_index = |copy ebml_w| add_to_index_(item, ebml_w, index);
 
+    debug!("encoding info for item at %s",
+           syntax::codemap::span_to_str(item.span, ecx.tcx.sess.codemap));
+
     match item.node {
       item_const(_, _) => {
         add_to_index();
@@ -738,7 +741,7 @@ fn encode_info_for_item(ecx: @encode_ctxt, ebml_w: ebml::Serializer,
             }
         }
         do opt_trait.iter() |associated_trait| {
-           encode_trait_ref(ebml_w, ecx, *associated_trait)
+           encode_trait_ref(ebml_w, ecx, *associated_trait);
         }
         encode_path(ecx, ebml_w, path, ast_map::path_name(item.ident));
         ebml_w.end_tag();

src/rustc/middle/typeck/collect.rs

@@ -522,10 +522,20 @@ fn convert(ccx: @crate_ctxt, it: @ast::item) {
                            region_param: rp,
                            ty: selfty});
 
-        for ms_opt.each |ms| {
-            let cms = convert_methods(ccx, *ms, rp, i_bounds);
-            for trait_ref.each |t| {
-                check_methods_against_trait(ccx, tps, rp, selfty, *t, cms);
+        match ms_opt {
+            Some(ref ms) => {
+                let cms = convert_methods(ccx, *ms, rp, i_bounds);
+                for trait_ref.each |t| {
+                    check_methods_against_trait(ccx, tps, rp, selfty, *t,
+                                                cms);
+                }
+            }
+            None => {
+                // We still need to instantiate the trait ref here so that
+                // metadata encoding will find the type.
+                for trait_ref.each |trait_ref| {
+                    let _ = instantiate_trait_ref(ccx, *trait_ref, rp);
+                }
             }
         }
       }