Fix a latent bug in trait dispatch where we sometimes counted associated types

when constructing the vtable-index. Not good.

src/librustc/middle/astencode.rs

@@ -904,8 +904,8 @@ impl<'a, 'tcx> rbml_writer_helpers<'tcx> for Encoder<'a> {
                             try!(this.emit_struct_field("method_num", 0, |this| {
                                 this.emit_uint(o.method_num)
                             }));
-                            try!(this.emit_struct_field("real_index", 0, |this| {
-                                this.emit_uint(o.real_index)
+                            try!(this.emit_struct_field("vtable_index", 0, |this| {
+                                this.emit_uint(o.vtable_index)
                             }));
                             Ok(())
                         })
@@ -1492,8 +1492,8 @@ impl<'a, 'tcx> rbml_decoder_decoder_helpers<'tcx> for reader::Decoder<'a> {
                                             this.read_uint()
                                         }).unwrap()
                                     },
-                                    real_index: {
-                                        this.read_struct_field("real_index", 3, |this| {
+                                    vtable_index: {
+                                        this.read_struct_field("vtable_index", 3, |this| {
                                             this.read_uint()
                                         }).unwrap()
                                     },

src/librustc/middle/traits/select.rs

@@ -214,7 +214,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         self.closure_typer.param_env()
     }
 
-    pub fn closure_typer(&self) -> &'cx (ty::UnboxedClosureTyper<'tcx>+'cx) {
+    pub fn closure_typer(&self) -> &'cx (ty::ClosureTyper<'tcx>+'cx) {
         self.closure_typer
     }
 

src/librustc/middle/traits/util.rs

@@ -329,58 +329,67 @@ pub fn upcast<'tcx>(tcx: &ty::ctxt<'tcx>,
 pub fn get_vtable_index_of_object_method<'tcx>(tcx: &ty::ctxt<'tcx>,
                                                object_trait_ref: ty::PolyTraitRef<'tcx>,
                                                trait_def_id: ast::DefId,
-                                               method_index_in_trait: uint) -> uint {
+                                               method_offset_in_trait: uint) -> uint {
     // We need to figure the "real index" of the method in a
     // listing of all the methods of an object. We do this by
     // iterating down the supertraits of the object's trait until
     // we find the trait the method came from, counting up the
     // methods from them.
     let mut method_count = 0;
-    ty::each_bound_trait_and_supertraits(tcx, &[object_trait_ref], |bound_ref| {
+
+    for bound_ref in transitive_bounds(tcx, &[object_trait_ref]) {
         if bound_ref.def_id() == trait_def_id {
-            false
-        } else {
-            let trait_items = ty::trait_items(tcx, bound_ref.def_id());
-            for trait_item in trait_items.iter() {
-                match *trait_item {
-                    ty::MethodTraitItem(_) => method_count += 1,
-                    ty::TypeTraitItem(_) => {}
-                }
-            }
-            true
+            break;
         }
+
+        let trait_items = ty::trait_items(tcx, bound_ref.def_id());
+        for trait_item in trait_items.iter() {
+            match *trait_item {
+                ty::MethodTraitItem(_) => method_count += 1,
+                ty::TypeTraitItem(_) => {}
+            }
+        }
+    }
+
+    // count number of methods preceding the one we are selecting and
+    // add them to the total offset; skip over associated types.
+    let trait_items = ty::trait_items(tcx, trait_def_id);
+    for trait_item in trait_items.iter().take(method_offset_in_trait) {
+        match *trait_item {
+            ty::MethodTraitItem(_) => method_count += 1,
+            ty::TypeTraitItem(_) => {}
+        }
+    }
+
+    // the item at the offset we were given really ought to be a method
+    assert!(match trait_items[method_offset_in_trait] {
+        ty::MethodTraitItem(_) => true,
+        ty::TypeTraitItem(_) => false
     });
-    method_count + method_index_in_trait
+
+    method_count
 }
 
-pub fn unboxed_closure_trait_ref_and_return_type<'tcx>(
-    closure_typer: &ty::UnboxedClosureTyper<'tcx>,
+pub enum TupleArgumentsFlag { Yes, No }
+
+pub fn closure_trait_ref_and_return_type<'tcx>(
+    tcx: &ty::ctxt<'tcx>,
     fn_trait_def_id: ast::DefId,
     self_ty: Ty<'tcx>,
-    closure_def_id: ast::DefId,
-    substs: &Substs<'tcx>)
+    sig: &ty::PolyFnSig<'tcx>,
+    tuple_arguments: TupleArgumentsFlag)
     -> ty::Binder<(Rc<ty::TraitRef<'tcx>>, Ty<'tcx>)>
 {
-    let tcx = closure_typer.param_env().tcx;
-    let closure_type = closure_typer.unboxed_closure_type(closure_def_id, substs);
-
-    debug!("unboxed_closure_trait_ref: closure_def_id={} closure_type={}",
-           closure_def_id.repr(tcx),
-           closure_type.repr(tcx));
-
-    let closure_sig = &closure_type.sig;
-    let arguments_tuple = closure_sig.0.inputs[0];
-    let trait_substs =
-        Substs::new_trait(
-            vec![arguments_tuple],
-            vec![],
-            self_ty);
+    let arguments_tuple = match tuple_arguments {
+        TupleArgumentsFlag::No => sig.0.inputs[0],
+        TupleArgumentsFlag::Yes => ty::mk_tup(tcx, sig.0.inputs.to_vec()),
+    };
+    let trait_substs = Substs::new_trait(vec![arguments_tuple], vec![], self_ty);
     let trait_ref = Rc::new(ty::TraitRef {
         def_id: fn_trait_def_id,
         substs: tcx.mk_substs(trait_substs),
     });
-
-    ty::Binder((trait_ref, closure_sig.0.output.unwrap()))
+    ty::Binder((trait_ref, sig.0.output.unwrap()))
 }
 
 impl<'tcx,O:Repr<'tcx>> Repr<'tcx> for super::Obligation<'tcx, O> {

src/librustc/middle/ty.rs

@@ -452,7 +452,10 @@ pub struct MethodParam<'tcx> {
     // never contains bound regions; those regions should have been
     // instantiated with fresh variables at this point.
     pub trait_ref: Rc<ty::TraitRef<'tcx>>,
-    // index of uint in the list of methods for the trait
+
+    // index of uint in the list of trait items. Note that this is NOT
+    // the index into the vtable, because the list of trait items
+    // includes associated types.
     pub method_num: uint,
 
     /// The impl for the trait from which the method comes. This
@@ -471,14 +474,14 @@ pub struct MethodObject<'tcx> {
     // the actual base trait id of the object
     pub object_trait_id: ast::DefId,
 
-    // index of the method to be invoked amongst the trait's methods
+    // index of the method to be invoked amongst the trait's items
     pub method_num: uint,
 
     // index into the actual runtime vtable.
     // the vtable is formed by concatenating together the method lists of
-    // the base object trait and all supertraits;  this is the index into
+    // the base object trait and all supertraits; this is the index into
     // that vtable
-    pub real_index: uint,
+    pub vtable_index: uint,
 }
 
 #[derive(Clone)]

src/librustc/middle/ty_fold.rs

@@ -319,7 +319,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::MethodOrigin<'tcx> {
                     trait_ref: object.trait_ref.fold_with(folder),
                     object_trait_id: object.object_trait_id,
                     method_num: object.method_num,
-                    real_index: object.real_index
+                    vtable_index: object.vtable_index,
                 })
             }
         }

src/librustc/util/ppaux.rs

@@ -1061,7 +1061,7 @@ impl<'tcx> Repr<'tcx> for ty::MethodObject<'tcx> {
         format!("MethodObject({},{},{})",
                 self.trait_ref.repr(tcx),
                 self.method_num,
-                self.real_index)
+                self.vtable_index)
     }
 }