resolve instances to ty::Instance directly

This removes the duplication between collector, callee, and (eventually)
MIRI.

15 files changed, 389 insertions, 495 deletions

diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 7e7d06e4b81..c71fc28b4d6 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -40,7 +40,7 @@ pub use self::select::{EvaluationCache, SelectionContext, SelectionCache};
 pub use self::select::{MethodMatchResult, MethodMatched, MethodAmbiguous, MethodDidNotMatch};
 pub use self::select::{MethodMatchedData}; // intentionally don't export variants
 pub use self::specialize::{OverlapError, specialization_graph, specializes, translate_substs};
-pub use self::specialize::{SpecializesCache, find_method};
+pub use self::specialize::{SpecializesCache, find_associated_item};
 pub use self::util::elaborate_predicates;
 pub use self::util::supertraits;
 pub use self::util::Supertraits;
diff --git a/src/librustc/traits/specialize/mod.rs b/src/librustc/traits/specialize/mod.rs
index 2c99ee21b0f..50a4d982832 100644
--- a/src/librustc/traits/specialize/mod.rs
+++ b/src/librustc/traits/specialize/mod.rs
@@ -29,8 +29,6 @@ use traits::{self, Reveal, ObligationCause};
 use ty::{self, TyCtxt, TypeFoldable};
 use syntax_pos::DUMMY_SP;
 
-use syntax::ast;
-
 pub mod specialization_graph;
 
 /// Information pertinent to an overlapping impl error.
@@ -106,22 +104,23 @@ pub fn translate_substs<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
 }
 
 /// Given a selected impl described by `impl_data`, returns the
-/// definition and substitions for the method with the name `name`,
-/// and trait method substitutions `substs`, in that impl, a less
-/// specialized impl, or the trait default, whichever applies.
-pub fn find_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                             name: ast::Name,
-                             substs: &'tcx Substs<'tcx>,
-                             impl_data: &super::VtableImplData<'tcx, ()>)
-                             -> (DefId, &'tcx Substs<'tcx>)
-{
+/// definition and substitions for the method with the name `name`
+/// the kind `kind`, and trait method substitutions `substs`, in
+/// that impl, a less specialized impl, or the trait default,
+/// whichever applies.
+pub fn find_associated_item<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    item: &ty::AssociatedItem,
+    substs: &'tcx Substs<'tcx>,
+    impl_data: &super::VtableImplData<'tcx, ()>,
+) -> (DefId, &'tcx Substs<'tcx>) {
     assert!(!substs.needs_infer());
 
     let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
     let trait_def = tcx.lookup_trait_def(trait_def_id);
 
     let ancestors = trait_def.ancestors(impl_data.impl_def_id);
-    match ancestors.defs(tcx, name, ty::AssociatedKind::Method).next() {
+    match ancestors.defs(tcx, item.name, item.kind).next() {
         Some(node_item) => {
             let substs = tcx.infer_ctxt((), Reveal::All).enter(|infcx| {
                 let substs = substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
@@ -137,7 +136,7 @@ pub fn find_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             (node_item.item.def_id, substs)
         }
         None => {
-            bug!("method {:?} not found in {:?}", name, impl_data.impl_def_id)
+            bug!("{:?} not found in {:?}", item, impl_data.impl_def_id)
         }
     }
 }
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index a0aeb4107c1..5543223105b 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -1469,6 +1469,15 @@ impl<T, R> InternIteratorElement<T, R> for T {
     }
 }
 
+impl<'a, T, R> InternIteratorElement<T, R> for &'a T
+    where T: Clone + 'a
+{
+    type Output = R;
+    fn intern_with<I: Iterator<Item=Self>, F: FnOnce(&[T]) -> R>(iter: I, f: F) -> Self::Output {
+        f(&iter.cloned().collect::<AccumulateVec<[_; 8]>>())
+    }
+}
+
 impl<T, R, E> InternIteratorElement<T, R> for Result<T, E> {
     type Output = Result<R, E>;
     fn intern_with<I: Iterator<Item=Self>, F: FnOnce(&[T]) -> R>(iter: I, f: F) -> Self::Output {
diff --git a/src/librustc/ty/instance.rs b/src/librustc/ty/instance.rs
index fdcfb3ebd3c..d93482acbcb 100644
--- a/src/librustc/ty/instance.rs
+++ b/src/librustc/ty/instance.rs
@@ -27,8 +27,17 @@ pub struct Instance<'tcx> {
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub enum InstanceDef<'tcx> {
     Item(DefId),
+    Intrinsic(DefId),
     // <fn() as FnTrait>::call_*
+    // def-id is FnTrait::call_*
     FnPtrShim(DefId, Ty<'tcx>),
+    // <Trait as Trait>::fn
+    Virtual(DefId, usize),
+    // <[mut closure] as FnOnce>::call_once
+    ClosureOnceShim {
+        call_once: DefId,
+        closure_did: DefId
+    },
 }
 
 impl<'tcx> InstanceDef<'tcx> {
@@ -36,8 +45,12 @@ impl<'tcx> InstanceDef<'tcx> {
     pub fn def_id(&self) -> DefId {
         match *self {
             InstanceDef::Item(def_id) |
-            InstanceDef::FnPtrShim(def_id, _)
-                => def_id
+            InstanceDef::FnPtrShim(def_id, _) |
+            InstanceDef::Virtual(def_id, _) |
+            InstanceDef::Intrinsic(def_id, ) |
+            InstanceDef::ClosureOnceShim {
+                call_once: def_id, closure_did: _
+            } => def_id
         }
     }
 
@@ -73,14 +86,23 @@ impl<'tcx> InstanceDef<'tcx> {
 
 impl<'tcx> fmt::Display for Instance<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        ppaux::parameterized(f, self.substs, self.def_id(), &[])?;
         match self.def {
-            InstanceDef::Item(def) => {
-                ppaux::parameterized(f, self.substs, def, &[])
+            InstanceDef::Item(_) => Ok(()),
+            InstanceDef::Intrinsic(_) => {
+                write!(f, " - intrinsic")
             }
-            InstanceDef::FnPtrShim(def, ty) => {
-                ppaux::parameterized(f, self.substs, def, &[])?;
+            InstanceDef::Virtual(_, num) => {
+                write!(f, " - shim(#{})", num)
+            }
+            InstanceDef::FnPtrShim(_, ty) => {
                 write!(f, " - shim({:?})", ty)
             }
+            InstanceDef::ClosureOnceShim {
+                call_once: _, closure_did
+            } => {
+                write!(f, " - shim({:?})", closure_did)
+            }
         }
     }
 }
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index 2344305fa9a..1d816d342c4 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -408,8 +408,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
         })
     }
-
-
 }
 
 pub struct TypeIdHasher<'a, 'gcx: 'a+'tcx, 'tcx: 'a, W> {
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index bf0b1796dff..2a053535e7e 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -41,6 +41,7 @@ fn make_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
         ty::InstanceDef::FnPtrShim(_, ty) => {
             build_fn_ptr_shim(tcx, ty, instance.def_ty(tcx))
         }
+        _ => bug!("unknown shim kind")
     };
     debug!("make_shim({:?}) = {:?}", instance, result);
 
diff --git a/src/librustc_trans/base.rs b/src/librustc_trans/base.rs
index ce767468c01..10ab199671f 100644
--- a/src/librustc_trans/base.rs
+++ b/src/librustc_trans/base.rs
@@ -36,9 +36,7 @@ use llvm::{Linkage, ValueRef, Vector, get_param};
 use llvm;
 use rustc::hir::def_id::LOCAL_CRATE;
 use middle::lang_items::StartFnLangItem;
-use rustc::traits;
 use rustc::ty::{self, Ty, TyCtxt};
-use rustc::ty::adjustment::CustomCoerceUnsized;
 use rustc::dep_graph::{AssertDepGraphSafe, DepNode, WorkProduct};
 use rustc::hir::map as hir_map;
 use rustc::util::common::time;
@@ -54,7 +52,6 @@ use common::{C_bool, C_bytes_in_context, C_i32, C_uint};
 use collector::{self, TransItemCollectionMode};
 use common::{C_struct_in_context, C_u64, C_undef};
 use common::CrateContext;
-use common::{fulfill_obligation};
 use common::{type_is_zero_size, val_ty};
 use common;
 use consts;
@@ -80,7 +77,7 @@ use std::ffi::{CStr, CString};
 use std::rc::Rc;
 use std::str;
 use std::i32;
-use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::Span;
 use syntax::attr;
 use rustc::hir;
 use rustc::ty::layout::{self, Layout};
@@ -313,25 +310,6 @@ pub fn coerce_unsized_into<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
     }
 }
 
-pub fn custom_coerce_unsize_info<'scx, 'tcx>(scx: &SharedCrateContext<'scx, 'tcx>,
-                                             source_ty: Ty<'tcx>,
-                                             target_ty: Ty<'tcx>)
-                                             -> CustomCoerceUnsized {
-    let trait_ref = ty::Binder(ty::TraitRef {
-        def_id: scx.tcx().lang_items.coerce_unsized_trait().unwrap(),
-        substs: scx.tcx().mk_substs_trait(source_ty, &[target_ty])
-    });
-
-    match fulfill_obligation(scx, DUMMY_SP, trait_ref) {
-        traits::VtableImpl(traits::VtableImplData { impl_def_id, .. }) => {
-            scx.tcx().custom_coerce_unsized_kind(impl_def_id)
-        }
-        vtable => {
-            bug!("invalid CoerceUnsized vtable: {:?}", vtable);
-        }
-    }
-}
-
 pub fn cast_shift_expr_rhs(
     cx: &Builder, op: hir::BinOp_, lhs: ValueRef, rhs: ValueRef
 ) -> ValueRef {
diff --git a/src/librustc_trans/callee.rs b/src/librustc_trans/callee.rs
index 2294e8a0002..70da2a69ef4 100644
--- a/src/librustc_trans/callee.rs
+++ b/src/librustc_trans/callee.rs
@@ -19,13 +19,13 @@ pub use self::CalleeData::*;
 use llvm::{self, ValueRef, get_params};
 use rustc::hir::def_id::DefId;
 use rustc::ty::subst::{Substs, Subst};
-use rustc::traits;
 use abi::{Abi, FnType};
 use attributes;
 use builder::Builder;
 use common::{self, CrateContext};
 use cleanup::CleanupScope;
 use mir::lvalue::LvalueRef;
+use monomorphize;
 use consts;
 use common::instance_ty;
 use declare;
@@ -38,8 +38,6 @@ use type_of;
 use rustc::ty::{self, Ty, TypeFoldable};
 use std::iter;
 
-use syntax_pos::DUMMY_SP;
-
 use mir::lvalue::Alignment;
 
 #[derive(Debug)]
@@ -60,94 +58,39 @@ pub struct Callee<'tcx> {
 }
 
 impl<'tcx> Callee<'tcx> {
-    /// Function pointer.
-    pub fn ptr(llfn: ValueRef, ty: Ty<'tcx>) -> Callee<'tcx> {
-        Callee {
-            data: Fn(llfn),
-            ty: ty
-        }
-    }
-
     /// Function or method definition.
     pub fn def<'a>(ccx: &CrateContext<'a, 'tcx>, def_id: DefId, substs: &'tcx Substs<'tcx>)
                    -> Callee<'tcx> {
-        let tcx = ccx.tcx();
-
-        if let Some(trait_id) = tcx.trait_of_item(def_id) {
-            return Callee::trait_method(ccx, trait_id, def_id, substs);
-        }
-
-        let instance = ty::Instance::new(def_id, substs);
-        let fn_ty = instance_ty(ccx.shared(), &instance);
-        if let ty::TyFnDef(.., f) = fn_ty.sty {
-            if f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic {
-                return Callee {
-                    data: Intrinsic,
-                    ty: fn_ty
+        let instance = monomorphize::resolve(ccx.shared(), def_id, substs);
+        let ty = instance_ty(ccx.shared(), &instance);
+        let data = match instance.def {
+            ty::InstanceDef::Intrinsic(_) => Intrinsic,
+            ty::InstanceDef::ClosureOnceShim { .. } => {
+                let closure_ty = instance.substs.type_at(0);
+                let (closure_def_id, closure_substs) = match closure_ty.sty {
+                    ty::TyClosure(def_id, substs) => (def_id, substs),
+                    _ => bug!("bad closure instance {:?}", instance)
                 };
-            }
-        }
-
-        let (llfn, ty) = get_fn(ccx, instance);
-        Callee::ptr(llfn, ty)
-    }
 
-    /// Trait method, which has to be resolved to an impl method.
-    pub fn trait_method<'a>(ccx: &CrateContext<'a, 'tcx>,
-                            trait_id: DefId,
-                            def_id: DefId,
-                            substs: &'tcx Substs<'tcx>)
-                            -> Callee<'tcx> {
-        let tcx = ccx.tcx();
-
-        let trait_ref = ty::TraitRef::from_method(tcx, trait_id, substs);
-        let trait_ref = tcx.normalize_associated_type(&ty::Binder(trait_ref));
-        match common::fulfill_obligation(ccx.shared(), DUMMY_SP, trait_ref) {
-            traits::VtableImpl(vtable_impl) => {
-                let name = tcx.item_name(def_id);
-                let instance = common::find_method(tcx, name, substs, &vtable_impl);
-
-                // Translate the function, bypassing Callee::def.
-                // That is because default methods have the same ID as the
-                // trait method used to look up the impl method that ended
-                // up here, so calling Callee::def would infinitely recurse.
-                let (llfn, ty) = get_fn(ccx, instance);
-                Callee::ptr(llfn, ty)
-            }
-            traits::VtableClosure(vtable_closure) => {
-                // The substitutions should have no type parameters remaining
-                // after passing through fulfill_obligation
-                let trait_closure_kind = tcx.lang_items.fn_trait_kind(trait_id).unwrap();
-                let instance = Instance::new(def_id, substs);
-                let llfn = trans_closure_method(
+                Fn(trans_fn_once_adapter_shim(
                     ccx,
-                    vtable_closure.closure_def_id,
-                    vtable_closure.substs,
+                    closure_def_id,
+                    closure_substs,
                     instance,
-                    trait_closure_kind);
-
-                let method_ty = instance_ty(ccx.shared(), &instance);
-                Callee::ptr(llfn, method_ty)
-            }
-            traits::VtableFnPointer(data) => {
-                let instance = ty::Instance {
-                    def: ty::InstanceDef::FnPtrShim(def_id, data.fn_ty),
-                    substs: substs,
-                };
-
-                let (llfn, ty) = get_fn(ccx, instance);
-                Callee::ptr(llfn, ty)
+                    get_fn(
+                        ccx,
+                        Instance::new(closure_def_id, closure_substs.substs)
+                    )
+                ))
             }
-            traits::VtableObject(ref data) => {
-                Callee {
-                    data: Virtual(tcx.get_vtable_index_of_object_method(data, def_id)),
-                    ty: instance_ty(ccx.shared(), &Instance::new(def_id, substs))
-                }
+            ty::InstanceDef::Virtual(_, n) => Virtual(n),
+            ty::InstanceDef::FnPtrShim(..) |
+            ty::InstanceDef::Item(..) => {
+                Fn(get_fn(ccx, instance))
             }
-            vtable => {
-                bug!("resolved vtable bad vtable {:?} in trans", vtable);
-            }
-        }
+        };
+
+        Callee { data, ty }
     }
 
     /// Get the abi::FnType for a direct call. Mainly deals with the fact
@@ -155,7 +98,8 @@ impl<'tcx> Callee<'tcx> {
     /// The extra argument types are for variadic (extern "C") functions.
     pub fn direct_fn_type<'a>(&self, ccx: &CrateContext<'a, 'tcx>,
                               extra_args: &[Ty<'tcx>]) -> FnType {
-        let sig = ccx.tcx().erase_late_bound_regions_and_normalize(&self.ty.fn_sig());
+        let sig = common::ty_fn_sig(ccx, self.ty);
+        let sig = ccx.tcx().erase_late_bound_regions_and_normalize(&sig);
         let mut fn_ty = FnType::unadjusted(ccx, sig, extra_args);
         if let Virtual(_) = self.data {
             // Don't pass the vtable, it's not an argument of the virtual fn.
@@ -175,72 +119,6 @@ impl<'tcx> Callee<'tcx> {
     }
 }
 
-fn trans_closure_method<'a, 'tcx>(ccx: &'a CrateContext<'a, 'tcx>,
-                                  def_id: DefId,
-                                  substs: ty::ClosureSubsts<'tcx>,
-                                  method_instance: Instance<'tcx>,
-                                  trait_closure_kind: ty::ClosureKind)
-                                  -> ValueRef
-{
-    // If this is a closure, redirect to it.
-    let (llfn, _) = get_fn(ccx, Instance::new(def_id, substs.substs));
-
-    // If the closure is a Fn closure, but a FnOnce is needed (etc),
-    // then adapt the self type
-    let llfn_closure_kind = ccx.tcx().closure_kind(def_id);
-
-    debug!("trans_closure_adapter_shim(llfn_closure_kind={:?}, \
-           trait_closure_kind={:?}, llfn={:?})",
-           llfn_closure_kind, trait_closure_kind, Value(llfn));
-
-    match needs_fn_once_adapter_shim(llfn_closure_kind, trait_closure_kind) {
-        Ok(true) => trans_fn_once_adapter_shim(ccx,
-                                               def_id,
-                                               substs,
-                                               method_instance,
-                                               llfn),
-        Ok(false) => llfn,
-        Err(()) => {
-            bug!("trans_closure_adapter_shim: cannot convert {:?} to {:?}",
-                 llfn_closure_kind,
-                 trait_closure_kind);
-        }
-    }
-}
-
-pub fn needs_fn_once_adapter_shim(actual_closure_kind: ty::ClosureKind,
-                                  trait_closure_kind: ty::ClosureKind)
-                                  -> Result<bool, ()>
-{
-    match (actual_closure_kind, trait_closure_kind) {
-        (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
-        (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
-        (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
-            // No adapter needed.
-           Ok(false)
-        }
-        (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
-            // The closure fn `llfn` is a `fn(&self, ...)`.  We want a
-            // `fn(&mut self, ...)`. In fact, at trans time, these are
-            // basically the same thing, so we can just return llfn.
-            Ok(false)
-        }
-        (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
-        (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
-            // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
-            // self, ...)`.  We want a `fn(self, ...)`. We can produce
-            // this by doing something like:
-            //
-            //     fn call_once(self, ...) { call_mut(&self, ...) }
-            //     fn call_once(mut self, ...) { call_mut(&mut self, ...) }
-            //
-            // These are both the same at trans time.
-            Ok(true)
-        }
-        _ => Err(()),
-    }
-}
-
 fn trans_fn_once_adapter_shim<'a, 'tcx>(
     ccx: &'a CrateContext<'a, 'tcx>,
     def_id: DefId,
@@ -307,7 +185,6 @@ fn trans_fn_once_adapter_shim<'a, 'tcx>(
     // the first argument (`self`) will be the (by value) closure env.
 
     let mut llargs = get_params(lloncefn);
-    let fn_ret = callee.ty.fn_ret();
     let fn_ty = callee.direct_fn_type(bcx.ccx, &[]);
     let self_idx = fn_ty.ret.is_indirect() as usize;
     let env_arg = &orig_fn_ty.args[0];
@@ -344,7 +221,7 @@ fn trans_fn_once_adapter_shim<'a, 'tcx>(
     }
     fn_ty.apply_attrs_callsite(llret);
 
-    if fn_ret.0.is_never() {
+    if sig.output().is_never() {
         bcx.unreachable();
     } else {
         self_scope.trans(&bcx);
@@ -372,7 +249,8 @@ fn trans_fn_once_adapter_shim<'a, 'tcx>(
 /// - `substs`: values for each of the fn/method's parameters
 fn get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
                     instance: Instance<'tcx>)
-                    -> (ValueRef, Ty<'tcx>) {
+                    -> ValueRef
+{
     let tcx = ccx.tcx();
 
     debug!("get_fn(instance={:?})", instance);
@@ -383,7 +261,7 @@ fn get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 
     let fn_ty = common::instance_ty(ccx.shared(), &instance);
     if let Some(&llfn) = ccx.instances().borrow().get(&instance) {
-        return (llfn, fn_ty);
+        return llfn;
     }
 
     let sym = ccx.symbol_map().get_or_compute(ccx.shared(),
@@ -455,5 +333,5 @@ fn get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 
     ccx.instances().borrow_mut().insert(instance, llfn);
 
-    (llfn, fn_ty)
+    llfn
 }
diff --git a/src/librustc_trans/collector.rs b/src/librustc_trans/collector.rs
index c4239fa2ae6..9476ffc9444 100644
--- a/src/librustc_trans/collector.rs
+++ b/src/librustc_trans/collector.rs
@@ -203,11 +203,8 @@ use rustc::mir::visit as mir_visit;
 use rustc::mir::visit::Visitor as MirVisitor;
 
 use syntax::abi::Abi;
-use syntax_pos::DUMMY_SP;
-use base::custom_coerce_unsize_info;
-use callee::needs_fn_once_adapter_shim;
 use context::SharedCrateContext;
-use common::{def_ty, find_method, instance_ty, fulfill_obligation};
+use common::{def_ty, instance_ty};
 use glue::{self, DropGlueKind};
 use monomorphize::{self, Instance};
 use util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
@@ -555,7 +552,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                         let substs = monomorphize::apply_param_substs(self.scx,
                                                                       self.param_substs,
                                                                       &substs);
-                        let instance = monomorphize::resolve_const(self.scx, def_id, substs);
+                        let instance = monomorphize::resolve(self.scx, def_id, substs);
                         collect_neighbours(self.scx, instance, self.output);
                     }
 
@@ -580,32 +577,23 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
             let callee_substs = monomorphize::apply_param_substs(self.scx,
                                                                  self.param_substs,
                                                                  &callee_substs);
-            let dispatched = do_static_dispatch(self.scx,
-                                                callee_def_id,
-                                                callee_substs);
-
-            if let StaticDispatchResult::Dispatched {
-                instance, fn_once_adjustment
-            } = dispatched {
-                // if we have a concrete impl (which we might not have
-                // in the case of something compiler generated like an
-                // object shim or a closure that is handled differently),
-                // we check if the callee is something that will actually
-                // result in a translation item ...
-                if should_trans_locally(self.scx.tcx(), &instance) {
-                    self.output.push(create_fn_trans_item(instance));
-
-                    // This call will instantiate an FnOnce adapter, which drops
-                    // the closure environment. Therefore we need to make sure
-                    // that we collect the drop-glue for the environment type.
-                    if let Some(env_ty) = fn_once_adjustment {
-                        let env_ty = glue::get_drop_glue_type(self.scx, env_ty);
-                        if self.scx.type_needs_drop(env_ty) {
-                            let dg = DropGlueKind::Ty(env_ty);
-                            self.output.push(TransItem::DropGlue(dg));
-                        }
+            let instance =
+                monomorphize::resolve(self.scx, callee_def_id, callee_substs);
+            if should_trans_locally(self.scx.tcx(), &instance) {
+                if let ty::InstanceDef::ClosureOnceShim { .. } = instance.def {
+                    // This call will instantiate an FnOnce adapter, which
+                    // drops the closure environment. Therefore we need to
+                    // make sure that we collect the drop-glue for the
+                    // environment type.
+
+                    let env_ty = instance.substs.type_at(0);
+                    let env_ty = glue::get_drop_glue_type(self.scx, env_ty);
+                    if self.scx.type_needs_drop(env_ty) {
+                        let dg = DropGlueKind::Ty(env_ty);
+                        self.output.push(TransItem::DropGlue(dg));
                     }
                 }
+                self.output.push(create_fn_trans_item(instance));
             }
         }
 
@@ -664,8 +652,13 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
 fn should_trans_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: &Instance<'tcx>)
                                   -> bool {
     let def_id = match instance.def {
-        ty::InstanceDef::Item(def_id) => def_id,
-        ty::InstanceDef::FnPtrShim(..) => return true
+        ty::InstanceDef::Item(def_id) |
+        ty::InstanceDef::ClosureOnceShim {
+            call_once: _, closure_did: def_id
+        } => def_id,
+        ty::InstanceDef::FnPtrShim(..) => return true,
+        ty::InstanceDef::Virtual(..) |
+        ty::InstanceDef::Intrinsic(_) => return false
     };
     match tcx.hir.get_if_local(def_id) {
         Some(hir_map::NodeForeignItem(..)) => {
@@ -718,31 +711,21 @@ fn find_drop_glue_neighbors<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
 
     // If the type implements Drop, also add a translation item for the
     // monomorphized Drop::drop() implementation.
-    let destructor = match ty.sty {
-        ty::TyAdt(def, _) => def.destructor(scx.tcx()),
-        _ => None
+    let has_dtor = match ty.sty {
+        ty::TyAdt(def, _) => def.has_dtor(scx.tcx()),
+        _ => false
     };
 
-    if let (Some(destructor), false) = (destructor, ty.is_box()) {
-        use rustc::ty::ToPolyTraitRef;
-
+    if has_dtor && !ty.is_box() {
         let drop_trait_def_id = scx.tcx()
                                    .lang_items
                                    .drop_trait()
                                    .unwrap();
-
-        let self_type_substs = scx.tcx().mk_substs_trait(ty, &[]);
-
-        let trait_ref = ty::TraitRef {
-            def_id: drop_trait_def_id,
-            substs: self_type_substs,
-        }.to_poly_trait_ref();
-
-        let substs = match fulfill_obligation(scx, DUMMY_SP, trait_ref) {
-            traits::VtableImpl(data) => data.substs,
-            _ => bug!()
-        };
-        let instance = Instance::new(destructor.did, substs);
+        let drop_method = scx.tcx().associated_items(drop_trait_def_id)
+            .find(|it| it.kind == ty::AssociatedKind::Method)
+            .unwrap().def_id;
+        let substs = scx.tcx().mk_substs_trait(ty, &[]);
+        let instance = monomorphize::resolve(scx, drop_method, substs);
         if should_trans_locally(scx.tcx(), &instance) {
             output.push(create_fn_trans_item(instance));
         }
@@ -817,115 +800,6 @@ fn find_drop_glue_neighbors<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
     }
 }
 
-enum StaticDispatchResult<'tcx> {
-    // The call could be resolved statically as going to the method with
-    // `instance`.
-    Dispatched {
-        instance: Instance<'tcx>,
-        // If this is a call to a closure that needs an FnOnce adjustment,
-        // this contains the new self type of the call (= type of the closure
-        // environment)
-        fn_once_adjustment: Option<ty::Ty<'tcx>>,
-    },
-    // This goes to somewhere that we don't know at compile-time
-    Unknown
-}
-
-fn do_static_dispatch<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
-                                fn_def_id: DefId,
-                                fn_substs: &'tcx Substs<'tcx>)
-                                -> StaticDispatchResult<'tcx> {
-    debug!("do_static_dispatch(fn_def_id={}, fn_substs={:?})",
-           def_id_to_string(scx.tcx(), fn_def_id),
-           fn_substs);
-    if let Some(trait_def_id) = scx.tcx().trait_of_item(fn_def_id) {
-        debug!(" => trait method, attempting to find impl");
-        do_static_trait_method_dispatch(scx,
-                                        &scx.tcx().associated_item(fn_def_id),
-                                        trait_def_id,
-                                        fn_substs)
-    } else {
-        debug!(" => regular function");
-        // The function is not part of an impl or trait, no dispatching
-        // to be done
-        StaticDispatchResult::Dispatched {
-            instance: Instance::new(fn_def_id, fn_substs),
-            fn_once_adjustment: None,
-        }
-    }
-}
-
-// Given a trait-method and substitution information, find out the actual
-// implementation of the trait method.
-fn do_static_trait_method_dispatch<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
-                                             trait_method: &ty::AssociatedItem,
-                                             trait_id: DefId,
-                                             rcvr_substs: &'tcx Substs<'tcx>)
-                                             -> StaticDispatchResult<'tcx> {
-    let tcx = scx.tcx();
-    debug!("do_static_trait_method_dispatch(trait_method={}, \
-                                            trait_id={}, \
-                                            rcvr_substs={:?})",
-           def_id_to_string(scx.tcx(), trait_method.def_id),
-           def_id_to_string(scx.tcx(), trait_id),
-           rcvr_substs);
-
-    let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
-    let vtbl = fulfill_obligation(scx, DUMMY_SP, ty::Binder(trait_ref));
-
-    // Now that we know which impl is being used, we can dispatch to
-    // the actual function:
-    match vtbl {
-        traits::VtableImpl(impl_data) => {
-            StaticDispatchResult::Dispatched {
-                instance: find_method(tcx, trait_method.name, rcvr_substs, &impl_data),
-                fn_once_adjustment: None,
-            }
-        }
-        traits::VtableClosure(closure_data) => {
-            let closure_def_id = closure_data.closure_def_id;
-            let trait_closure_kind = tcx.lang_items.fn_trait_kind(trait_id).unwrap();
-            let actual_closure_kind = tcx.closure_kind(closure_def_id);
-
-            let needs_fn_once_adapter_shim =
-                match needs_fn_once_adapter_shim(actual_closure_kind,
-                                                 trait_closure_kind) {
-                Ok(true) => true,
-                _ => false,
-            };
-
-            let fn_once_adjustment = if needs_fn_once_adapter_shim {
-                Some(tcx.mk_closure_from_closure_substs(closure_def_id,
-                                                        closure_data.substs))
-            } else {
-                None
-            };
-
-            StaticDispatchResult::Dispatched {
-                instance: Instance::new(closure_def_id, closure_data.substs.substs),
-                fn_once_adjustment: fn_once_adjustment,
-            }
-        }
-        traits::VtableFnPointer(ref data) => {
-            StaticDispatchResult::Dispatched {
-                instance: Instance {
-                    def: ty::InstanceDef::FnPtrShim(trait_method.def_id, data.fn_ty),
-                    substs: trait_ref.substs
-                },
-                fn_once_adjustment: None,
-            }
-        }
-        // Trait object shims are always instantiated in-place, and as they are
-        // just an ABI-adjusting indirect call they do not have any dependencies.
-        traits::VtableObject(..) => {
-            StaticDispatchResult::Unknown
-        }
-        _ => {
-            bug!("static call to invalid vtable: {:?}", vtbl)
-        }
-    }
-}
-
 /// For given pair of source and target type that occur in an unsizing coercion,
 /// this function finds the pair of types that determines the vtable linking
 /// them.
@@ -991,7 +865,8 @@ fn find_vtable_types_for_unsizing<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
          &ty::TyAdt(target_adt_def, target_substs)) => {
             assert_eq!(source_adt_def, target_adt_def);
 
-            let kind = custom_coerce_unsize_info(scx, source_ty, target_ty);
+            let kind =
+                monomorphize::custom_coerce_unsize_info(scx, source_ty, target_ty);
 
             let coerce_index = match kind {
                 CustomCoerceUnsized::Struct(i) => i
@@ -1017,6 +892,20 @@ fn find_vtable_types_for_unsizing<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
 
 fn create_fn_trans_item<'a, 'tcx>(instance: Instance<'tcx>) -> TransItem<'tcx> {
     debug!("create_fn_trans_item(instance={})", instance);
+    let instance = match instance.def {
+        ty::InstanceDef::ClosureOnceShim { .. } => {
+            // HACK: don't create ClosureOnce trans items for now
+            // have someone else generate the drop glue
+            let closure_ty = instance.substs.type_at(0);
+            match closure_ty.sty {
+                ty::TyClosure(def_id, substs) => {
+                    Instance::new(def_id, substs.substs)
+                }
+                _ => bug!("bad closure instance {:?}", instance)
+            }
+        }
+        _ => instance
+    };
     TransItem::Fn(instance)
 }
 
@@ -1037,18 +926,7 @@ fn create_trans_items_for_vtable_methods<'a, 'tcx>(scx: &SharedCrateContext<'a,
             // Walk all methods of the trait, including those of its supertraits
             let methods = traits::get_vtable_methods(scx.tcx(), poly_trait_ref);
             let methods = methods.filter_map(|method| method)
-                .filter_map(|(def_id, substs)| {
-                    if let StaticDispatchResult::Dispatched {
-                        instance,
-                        // We already add the drop-glue for the closure env
-                        // unconditionally below.
-                        fn_once_adjustment: _ ,
-                    } = do_static_dispatch(scx, def_id, substs) {
-                        Some(instance)
-                    } else {
-                        None
-                    }
-                })
+                .map(|(def_id, substs)| monomorphize::resolve(scx, def_id, substs))
                 .filter(|&instance| should_trans_locally(scx.tcx(), &instance))
                 .map(|instance| create_fn_trans_item(instance));
             output.extend(methods);
@@ -1203,18 +1081,11 @@ fn create_trans_items_for_default_impls<'a, 'tcx>(scx: &SharedCrateContext<'a, '
                         continue;
                     }
 
-                    // The substitutions we have are on the impl, so we grab
-                    // the method type from the impl to substitute into.
-                    let impl_substs = tcx.empty_substs_for_def_id(impl_def_id);
-                    let impl_data = traits::VtableImplData {
-                        impl_def_id: impl_def_id,
-                        substs: impl_substs,
-                        nested: vec![]
-                    };
-                    let instance = find_method(tcx, method.name, callee_substs, &impl_data);
+                    let instance =
+                        monomorphize::resolve(scx, method.def_id, callee_substs);
 
                     let predicates = tcx.item_predicates(instance.def_id()).predicates
-                        .subst(tcx, impl_substs);
+                        .subst(tcx, instance.substs);
                     if !traits::normalize_and_test_predicates(tcx, predicates) {
                         continue;
                     }
diff --git a/src/librustc_trans/common.rs b/src/librustc_trans/common.rs
index 4389207cdf2..431325c5ec7 100644
--- a/src/librustc_trans/common.rs
+++ b/src/librustc_trans/common.rs
@@ -17,7 +17,6 @@ use llvm::{ValueRef, ContextRef, TypeKind};
 use llvm::{True, False, Bool, OperandBundleDef};
 use rustc::hir::def_id::DefId;
 use rustc::hir::map::DefPathData;
-use rustc::util::common::MemoizationMap;
 use middle::lang_items::LangItem;
 use base;
 use builder::Builder;
@@ -30,13 +29,11 @@ use value::Value;
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::layout::Layout;
 use rustc::ty::subst::{Subst, Substs};
-use rustc::traits::{self, SelectionContext, Reveal};
 use rustc::hir;
 
 use libc::{c_uint, c_char};
 use std::iter;
 
-use syntax::ast;
 use syntax::attr;
 use syntax::symbol::InternedString;
 use syntax_pos::Span;
@@ -427,73 +424,6 @@ pub fn is_null(val: ValueRef) -> bool {
     }
 }
 
-/// Attempts to resolve an obligation. The result is a shallow vtable resolution -- meaning that we
-/// do not (necessarily) resolve all nested obligations on the impl. Note that type check should
-/// guarantee to us that all nested obligations *could be* resolved if we wanted to.
-pub fn fulfill_obligation<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
-                                    span: Span,
-                                    trait_ref: ty::PolyTraitRef<'tcx>)
-                                    -> traits::Vtable<'tcx, ()>
-{
-    let tcx = scx.tcx();
-
-    // Remove any references to regions; this helps improve caching.
-    let trait_ref = tcx.erase_regions(&trait_ref);
-
-    scx.trait_cache().memoize(trait_ref, || {
-        debug!("trans::fulfill_obligation(trait_ref={:?}, def_id={:?})",
-               trait_ref, trait_ref.def_id());
-
-        // Do the initial selection for the obligation. This yields the
-        // shallow result we are looking for -- that is, what specific impl.
-        tcx.infer_ctxt((), Reveal::All).enter(|infcx| {
-            let mut selcx = SelectionContext::new(&infcx);
-
-            let obligation_cause = traits::ObligationCause::misc(span,
-                                                             ast::DUMMY_NODE_ID);
-            let obligation = traits::Obligation::new(obligation_cause,
-                                                     trait_ref.to_poly_trait_predicate());
-
-            let selection = match selcx.select(&obligation) {
-                Ok(Some(selection)) => selection,
-                Ok(None) => {
-                    // Ambiguity can happen when monomorphizing during trans
-                    // expands to some humongo type that never occurred
-                    // statically -- this humongo type can then overflow,
-                    // leading to an ambiguous result. So report this as an
-                    // overflow bug, since I believe this is the only case
-                    // where ambiguity can result.
-                    debug!("Encountered ambiguity selecting `{:?}` during trans, \
-                            presuming due to overflow",
-                           trait_ref);
-                    tcx.sess.span_fatal(span,
-                        "reached the recursion limit during monomorphization \
-                         (selection ambiguity)");
-                }
-                Err(e) => {
-                    span_bug!(span, "Encountered error `{:?}` selecting `{:?}` during trans",
-                              e, trait_ref)
-                }
-            };
-
-            debug!("fulfill_obligation: selection={:?}", selection);
-
-            // Currently, we use a fulfillment context to completely resolve
-            // all nested obligations. This is because they can inform the
-            // inference of the impl's type parameters.
-            let mut fulfill_cx = traits::FulfillmentContext::new();
-            let vtable = selection.map(|predicate| {
-                debug!("fulfill_obligation: register_predicate_obligation {:?}", predicate);
-                fulfill_cx.register_predicate_obligation(&infcx, predicate);
-            });
-            let vtable = infcx.drain_fulfillment_cx_or_panic(span, &mut fulfill_cx, &vtable);
-
-            info!("Cache miss: {:?} => {:?}", trait_ref, vtable);
-            vtable
-        })
-    })
-}
-
 pub fn langcall(tcx: TyCtxt,
                 span: Option<Span>,
                 msg: &str,
@@ -617,6 +547,7 @@ pub fn requests_inline<'a, 'tcx>(
         _ => attr::requests_inline(&tcx.get_attrs(def_id)[..]),
     }
 }
+
 /// Given a DefId and some Substs, produces the monomorphic item type.
 pub fn def_ty<'a, 'tcx>(shared: &SharedCrateContext<'a, 'tcx>,
                         def_id: DefId,
@@ -635,14 +566,3 @@ pub fn instance_ty<'a, 'tcx>(shared: &SharedCrateContext<'a, 'tcx>,
     let ty = instance.def.def_ty(shared.tcx());
     monomorphize::apply_param_substs(shared, instance.substs, &ty)
 }
-
-pub fn find_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                             name: ast::Name,
-                             substs: &'tcx Substs<'tcx>,
-                             impl_data: &traits::VtableImplData<'tcx, ()>)
-                             -> ty::Instance<'tcx>
-{
-    let (def_id, substs) = traits::find_method(tcx, name, substs, impl_data);
-    let substs = tcx.erase_regions(&substs);
-    ty::Instance::new(def_id, substs)
-}
diff --git a/src/librustc_trans/glue.rs b/src/librustc_trans/glue.rs
index 35ebd67b5f8..2eb94aa56ab 100644
--- a/src/librustc_trans/glue.rs
+++ b/src/librustc_trans/glue.rs
@@ -39,7 +39,6 @@ use value::Value;
 use Disr;
 use builder::Builder;
 
-use syntax_pos::DUMMY_SP;
 use mir::lvalue::Alignment;
 
 pub fn trans_exchange_free_ty<'a, 'tcx>(bcx: &Builder<'a, 'tcx>, ptr: LvalueRef<'tcx>) {
@@ -241,8 +240,6 @@ pub fn implement_drop_glue<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, g: DropGlueKi
             let shallow_drop = def.is_union();
             let tcx = bcx.tcx();
 
-            let def = t.ty_adt_def().unwrap();
-
             // Be sure to put the contents into a scope so we can use an invoke
             // instruction to call the user destructor but still call the field
             // destructors if the user destructor panics.
@@ -256,17 +253,12 @@ pub fn implement_drop_glue<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, g: DropGlueKi
             } else {
                 CleanupScope::noop()
             };
-
-            let trait_ref = ty::Binder(ty::TraitRef {
-                def_id: tcx.lang_items.drop_trait().unwrap(),
-                substs: tcx.mk_substs_trait(t, &[])
-            });
-            let vtbl = match fulfill_obligation(bcx.ccx.shared(), DUMMY_SP, trait_ref) {
-                traits::VtableImpl(data) => data,
-                _ => bug!("dtor for {:?} is not an impl???", t)
-            };
-            let dtor_did = def.destructor(tcx).unwrap().did;
-            let callee = Callee::def(bcx.ccx, dtor_did, vtbl.substs);
+            let drop_trait_def_id = tcx.lang_items.drop_trait().unwrap();
+            let drop_method = tcx.associated_items(drop_trait_def_id)
+                .find(|it| it.kind == ty::AssociatedKind::Method)
+                .unwrap().def_id;
+            let self_type_substs = tcx.mk_substs_trait(t, &[]);
+            let callee = Callee::def(bcx.ccx, drop_method, self_type_substs);
             let fn_ty = callee.direct_fn_type(bcx.ccx, &[]);
             let llret;
             let args = &[ptr.llval, ptr.llextra][..1 + ptr.has_extra() as usize];
diff --git a/src/librustc_trans/lib.rs b/src/librustc_trans/lib.rs
index 1530fcda3d3..49cc0b5fad4 100644
--- a/src/librustc_trans/lib.rs
+++ b/src/librustc_trans/lib.rs
@@ -28,6 +28,7 @@
 #![feature(box_syntax)]
 #![feature(const_fn)]
 #![feature(custom_attribute)]
+#![cfg_attr(stage0, feature(field_init_shorthand))]
 #![allow(unused_attributes)]
 #![feature(i128_type)]
 #![feature(libc)]
diff --git a/src/librustc_trans/mir/constant.rs b/src/librustc_trans/mir/constant.rs
index deb1073cf9a..69009ab3560 100644
--- a/src/librustc_trans/mir/constant.rs
+++ b/src/librustc_trans/mir/constant.rs
@@ -249,7 +249,7 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                  substs: &'tcx Substs<'tcx>,
                  args: IndexVec<mir::Local, Const<'tcx>>)
                  -> Result<Const<'tcx>, ConstEvalErr<'tcx>> {
-        let instance = monomorphize::resolve_const(ccx.shared(), def_id, substs);
+        let instance = monomorphize::resolve(ccx.shared(), def_id, substs);
         let mir = ccx.tcx().instance_mir(instance.def);
         MirConstContext::new(ccx, &mir, instance.substs, args).trans()
     }
diff --git a/src/librustc_trans/monomorphize.rs b/src/librustc_trans/monomorphize.rs
index 3b746af275a..bf073d8b978 100644
--- a/src/librustc_trans/monomorphize.rs
+++ b/src/librustc_trans/monomorphize.rs
@@ -8,38 +8,260 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use abi::Abi;
 use common::*;
+
 use rustc::hir::def_id::DefId;
 use rustc::infer::TransNormalize;
-use rustc::traits;
+use rustc::traits::{self, SelectionContext, Reveal};
+use rustc::ty::adjustment::CustomCoerceUnsized;
 use rustc::ty::fold::{TypeFolder, TypeFoldable};
-use rustc::ty::subst::{Subst, Substs};
+use rustc::ty::subst::{Kind, Subst, Substs};
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::util::common::MemoizationMap;
 
-use syntax::codemap::DUMMY_SP;
+use syntax::ast;
+use syntax::codemap::{Span, DUMMY_SP};
 
 pub use rustc::ty::Instance;
 
-/// For associated constants from traits, return the impl definition.
-pub fn resolve_const<'a, 'tcx>(
-    scx: &SharedCrateContext<'a, 'tcx>, def_id: DefId, substs: &'tcx Substs<'tcx>
+fn fn_once_adapter_instance<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    closure_did: DefId,
+    substs: ty::ClosureSubsts<'tcx>,
+    ) -> Instance<'tcx> {
+    debug!("fn_once_adapter_shim({:?}, {:?})",
+           closure_did,
+           substs);
+    let fn_once = tcx.lang_items.fn_once_trait().unwrap();
+    let call_once = tcx.associated_items(fn_once)
+        .find(|it| it.kind == ty::AssociatedKind::Method)
+        .unwrap().def_id;
+    let def = ty::InstanceDef::ClosureOnceShim { call_once, closure_did };
+
+    let self_ty = tcx.mk_closure_from_closure_substs(
+        closure_did, substs);
+
+    let sig = tcx.closure_type(closure_did).subst(tcx, substs.substs);
+    let sig = tcx.erase_late_bound_regions_and_normalize(&sig);
+    assert_eq!(sig.inputs().len(), 1);
+    let substs = tcx.mk_substs([
+        Kind::from(self_ty),
+        Kind::from(sig.inputs()[0]),
+    ].iter().cloned());
+
+    debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
+    Instance { def, substs }
+}
+
+/// Attempts to resolve an obligation. The result is a shallow vtable resolution -- meaning that we
+/// do not (necessarily) resolve all nested obligations on the impl. Note that type check should
+/// guarantee to us that all nested obligations *could be* resolved if we wanted to.
+fn fulfill_obligation<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
+                                span: Span,
+                                trait_ref: ty::PolyTraitRef<'tcx>)
+                                -> traits::Vtable<'tcx, ()>
+{
+    let tcx = scx.tcx();
+
+    // Remove any references to regions; this helps improve caching.
+    let trait_ref = tcx.erase_regions(&trait_ref);
+
+    scx.trait_cache().memoize(trait_ref, || {
+        debug!("trans::fulfill_obligation(trait_ref={:?}, def_id={:?})",
+               trait_ref, trait_ref.def_id());
+
+        // Do the initial selection for the obligation. This yields the
+        // shallow result we are looking for -- that is, what specific impl.
+        tcx.infer_ctxt((), Reveal::All).enter(|infcx| {
+            let mut selcx = SelectionContext::new(&infcx);
+
+            let obligation_cause = traits::ObligationCause::misc(span,
+                                                             ast::DUMMY_NODE_ID);
+            let obligation = traits::Obligation::new(obligation_cause,
+                                                     trait_ref.to_poly_trait_predicate());
+
+            let selection = match selcx.select(&obligation) {
+                Ok(Some(selection)) => selection,
+                Ok(None) => {
+                    // Ambiguity can happen when monomorphizing during trans
+                    // expands to some humongo type that never occurred
+                    // statically -- this humongo type can then overflow,
+                    // leading to an ambiguous result. So report this as an
+                    // overflow bug, since I believe this is the only case
+                    // where ambiguity can result.
+                    debug!("Encountered ambiguity selecting `{:?}` during trans, \
+                            presuming due to overflow",
+                           trait_ref);
+                    tcx.sess.span_fatal(span,
+                        "reached the recursion limit during monomorphization \
+                         (selection ambiguity)");
+                }
+                Err(e) => {
+                    span_bug!(span, "Encountered error `{:?}` selecting `{:?}` during trans",
+                              e, trait_ref)
+                }
+            };
+
+            debug!("fulfill_obligation: selection={:?}", selection);
+
+            // Currently, we use a fulfillment context to completely resolve
+            // all nested obligations. This is because they can inform the
+            // inference of the impl's type parameters.
+            let mut fulfill_cx = traits::FulfillmentContext::new();
+            let vtable = selection.map(|predicate| {
+                debug!("fulfill_obligation: register_predicate_obligation {:?}", predicate);
+                fulfill_cx.register_predicate_obligation(&infcx, predicate);
+            });
+            let vtable = infcx.drain_fulfillment_cx_or_panic(span, &mut fulfill_cx, &vtable);
+
+            info!("Cache miss: {:?} => {:?}", trait_ref, vtable);
+            vtable
+        })
+    })
+}
+
+fn needs_fn_once_adapter_shim(actual_closure_kind: ty::ClosureKind,
+                              trait_closure_kind: ty::ClosureKind)
+                              -> Result<bool, ()>
+{
+    match (actual_closure_kind, trait_closure_kind) {
+        (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
+        (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
+        (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
+            // No adapter needed.
+           Ok(false)
+        }
+        (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
+            // The closure fn `llfn` is a `fn(&self, ...)`.  We want a
+            // `fn(&mut self, ...)`. In fact, at trans time, these are
+            // basically the same thing, so we can just return llfn.
+            Ok(false)
+        }
+        (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
+        (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
+            // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
+            // self, ...)`.  We want a `fn(self, ...)`. We can produce
+            // this by doing something like:
+            //
+            //     fn call_once(self, ...) { call_mut(&self, ...) }
+            //     fn call_once(mut self, ...) { call_mut(&mut self, ...) }
+            //
+            // These are both the same at trans time.
+            Ok(true)
+        }
+        _ => Err(()),
+    }
+}
+
+fn resolve_associated_item<'a, 'tcx>(
+    scx: &SharedCrateContext<'a, 'tcx>,
+    trait_item: &ty::AssociatedItem,
+    trait_id: DefId,
+    rcvr_substs: &'tcx Substs<'tcx>
 ) -> Instance<'tcx> {
-    if let Some(trait_id) = scx.tcx().trait_of_item(def_id) {
-        let trait_ref = ty::TraitRef::new(trait_id, substs);
-        let trait_ref = ty::Binder(trait_ref);
-        let vtable = fulfill_obligation(scx, DUMMY_SP, trait_ref);
-        if let traits::VtableImpl(vtable_impl) = vtable {
-            let name = scx.tcx().item_name(def_id);
-            let ac = scx.tcx().associated_items(vtable_impl.impl_def_id)
-                .find(|item| item.kind == ty::AssociatedKind::Const && item.name == name);
-            if let Some(ac) = ac {
-                return Instance::new(ac.def_id, vtable_impl.substs);
+    let tcx = scx.tcx();
+    let def_id = trait_item.def_id;
+    debug!("resolve_associated_item(trait_item={:?}, \
+                                    trait_id={:?}, \
+                                    rcvr_substs={:?})",
+           def_id, trait_id, rcvr_substs);
+
+    let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
+    let vtbl = fulfill_obligation(scx, DUMMY_SP, ty::Binder(trait_ref));
+
+    // Now that we know which impl is being used, we can dispatch to
+    // the actual function:
+    match vtbl {
+        traits::VtableImpl(impl_data) => {
+            let (def_id, substs) = traits::find_associated_item(
+                tcx, trait_item, rcvr_substs, &impl_data);
+            let substs = tcx.erase_regions(&substs);
+            ty::Instance::new(def_id, substs)
+        }
+        traits::VtableClosure(closure_data) => {
+            let closure_def_id = closure_data.closure_def_id;
+            let trait_closure_kind = tcx.lang_items.fn_trait_kind(trait_id).unwrap();
+            let actual_closure_kind = tcx.closure_kind(closure_def_id);
+
+            match needs_fn_once_adapter_shim(actual_closure_kind,
+                                             trait_closure_kind) {
+                Ok(true) => fn_once_adapter_instance(
+                    tcx, closure_def_id, closure_data.substs),
+                _ => Instance::new(closure_def_id, closure_data.substs.substs),
+            }
+        }
+        traits::VtableFnPointer(ref data) => {
+            Instance {
+                def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
+                substs: rcvr_substs
+            }
+        }
+        traits::VtableObject(ref data) => {
+            let index = tcx.get_vtable_index_of_object_method(data, def_id);
+            Instance {
+                def: ty::InstanceDef::Virtual(def_id, index),
+                substs: rcvr_substs
             }
         }
+        _ => {
+            bug!("static call to invalid vtable: {:?}", vtbl)
+        }
     }
+}
 
-    Instance::new(def_id, substs)
+/// The point where linking happens. Resolve a (def_id, substs)
+/// pair to an instance.
+pub fn resolve<'a, 'tcx>(
+    scx: &SharedCrateContext<'a, 'tcx>,
+    def_id: DefId,
+    substs: &'tcx Substs<'tcx>
+) -> Instance<'tcx> {
+    debug!("resolve(def_id={:?}, substs={:?})",
+           def_id, substs);
+    let result = if let Some(trait_def_id) = scx.tcx().trait_of_item(def_id) {
+        debug!(" => associated item, attempting to find impl");
+        let item = scx.tcx().associated_item(def_id);
+        resolve_associated_item(scx, &item, trait_def_id, substs)
+    } else {
+        let item_type = def_ty(scx, def_id, substs);
+        let def = match item_type.sty {
+            ty::TyFnDef(_, _, f) if
+                f.abi() == Abi::RustIntrinsic ||
+                f.abi() == Abi::PlatformIntrinsic =>
+            {
+                debug!(" => intrinsic");
+                ty::InstanceDef::Intrinsic(def_id)
+            }
+            _ => {
+                debug!(" => free item");
+                ty::InstanceDef::Item(def_id)
+            }
+        };
+        Instance { def, substs }
+    };
+    debug!("resolve(def_id={:?}, substs={:?}) = {}",
+           def_id, substs, result);
+    result
+}
+
+pub fn custom_coerce_unsize_info<'scx, 'tcx>(scx: &SharedCrateContext<'scx, 'tcx>,
+                                             source_ty: Ty<'tcx>,
+                                             target_ty: Ty<'tcx>)
+                                             -> CustomCoerceUnsized {
+    let trait_ref = ty::Binder(ty::TraitRef {
+        def_id: scx.tcx().lang_items.coerce_unsized_trait().unwrap(),
+        substs: scx.tcx().mk_substs_trait(source_ty, &[target_ty])
+    });
+
+    match fulfill_obligation(scx, DUMMY_SP, trait_ref) {
+        traits::VtableImpl(traits::VtableImplData { impl_def_id, .. }) => {
+            scx.tcx().custom_coerce_unsized_kind(impl_def_id)
+        }
+        vtable => {
+            bug!("invalid CoerceUnsized vtable: {:?}", vtable);
+        }
+    }
 }
 
 /// Monomorphizes a type from the AST by first applying the in-scope
diff --git a/src/librustc_trans/partitioning.rs b/src/librustc_trans/partitioning.rs
index 1232c6cd28e..d0cf32508d4 100644
--- a/src/librustc_trans/partitioning.rs
+++ b/src/librustc_trans/partitioning.rs
@@ -458,7 +458,10 @@ fn characteristic_def_id_of_trans_item<'a, 'tcx>(scx: &SharedCrateContext<'a, 't
         TransItem::Fn(instance) => {
             let def_id = match instance.def {
                 ty::InstanceDef::Item(def_id) => def_id,
-                ty::InstanceDef::FnPtrShim(..) => return None
+                ty::InstanceDef::FnPtrShim(..) |
+                ty::InstanceDef::ClosureOnceShim { .. } |
+                ty::InstanceDef::Intrinsic(..) |
+                ty::InstanceDef::Virtual(..) => return None
             };
 
             // If this is a method, we want to put it into the same module as