diff --git a/src/librustc/middle/traits/fulfill.rs b/src/librustc/middle/traits/fulfill.rs
index bf4273dbfd0..25c86be993f 100644
--- a/src/librustc/middle/traits/fulfill.rs
+++ b/src/librustc/middle/traits/fulfill.rs
@@ -11,6 +11,8 @@
 use middle::mem_categorization::Typer;
 use middle::ty;
 use middle::typeck::infer::InferCtxt;
+use std::collections::HashSet;
+use std::rc::Rc;
 use util::ppaux::Repr;
 
 use super::CodeAmbiguity;
@@ -30,6 +32,13 @@ use super::select::SelectionContext;
 /// method `select_all_or_error` can be used to report any remaining
 /// ambiguous cases as errors.
 pub struct FulfillmentContext<'tcx> {
+    // a simple cache that aims to cache *exact duplicate obligations*
+    // and avoid adding them twice. This serves a different purpose
+    // than the `SelectionCache`: it avoids duplicate errors and
+    // permits recursive obligations, which are often generated from
+    // traits like `Send` et al.
+    duplicate_set: HashSet<Rc<ty::TraitRef<'tcx>>>,
+
     // A list of all obligations that have been registered with this
     // fulfillment context.
     trait_obligations: Vec<Obligation<'tcx>>,
@@ -43,6 +52,7 @@ pub struct FulfillmentContext<'tcx> {
 impl<'tcx> FulfillmentContext<'tcx> {
     pub fn new() -> FulfillmentContext<'tcx> {
         FulfillmentContext {
+            duplicate_set: HashSet::new(),
             trait_obligations: Vec::new(),
             attempted_mark: 0,
         }
@@ -52,9 +62,13 @@ impl<'tcx> FulfillmentContext<'tcx> {
                                tcx: &ty::ctxt<'tcx>,
                                obligation: Obligation<'tcx>)
     {
-        debug!("register_obligation({})", obligation.repr(tcx));
-        assert!(!obligation.trait_ref.has_escaping_regions());
-        self.trait_obligations.push(obligation);
+        if self.duplicate_set.insert(obligation.trait_ref.clone()) {
+            debug!("register_obligation({})", obligation.repr(tcx));
+            assert!(!obligation.trait_ref.has_escaping_regions());
+            self.trait_obligations.push(obligation);
+        } else {
+            debug!("register_obligation({}) -- already seen, skip", obligation.repr(tcx));
+        }
     }
 
     pub fn select_all_or_error<'a>(&mut self,
diff --git a/src/librustc/middle/traits/select.rs b/src/librustc/middle/traits/select.rs
index 9ce6947731d..71a183b475c 100644
--- a/src/librustc/middle/traits/select.rs
+++ b/src/librustc/middle/traits/select.rs
@@ -113,7 +113,7 @@ pub enum MethodMatchedData {
 /// candidate is one that might match or might not, depending on how
 /// type variables wind up being resolved. This only occurs during inference.
 ///
-/// For selection to suceed, there must be exactly one non-ambiguous
+/// For selection to succeed, there must be exactly one non-ambiguous
 /// candidate.  Usually, it is not possible to have more than one
 /// definitive candidate, due to the coherence rules. However, there is
 /// one case where it could occur: if there is a blanket impl for a
@@ -1149,24 +1149,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                                              candidates: &mut CandidateSet<'tcx>)
                                              -> Result<(),SelectionError<'tcx>>
     {
-        // FIXME -- To be more like a normal impl, we should just
-        // ignore the nested cases here, and instead generate nested
-        // obligations in `confirm_candidate`. However, this doesn't
-        // work because we require handling the recursive cases to
-        // avoid infinite cycles (that is, with recursive types,
-        // sometimes `Foo : Copy` only holds if `Foo : Copy`).
-
         match self.builtin_bound(bound, stack.obligation.self_ty()) {
-            Ok(If(nested)) => {
-                debug!("builtin_bound: bound={} nested={}",
-                       bound.repr(self.tcx()),
-                       nested.repr(self.tcx()));
-                let data = self.vtable_builtin_data(stack.obligation, bound, nested);
-                match self.winnow_selection(Some(stack), VtableBuiltin(data)) {
-                    EvaluatedToOk => { Ok(candidates.vec.push(BuiltinCandidate(bound))) }
-                    EvaluatedToAmbig => { Ok(candidates.ambiguous = true) }
-                    EvaluatedToErr => { Err(Unimplemented) }
-                }
+            Ok(If(_)) => {
+                debug!("builtin_bound: bound={}",
+                       bound.repr(self.tcx()));
+                candidates.vec.push(BuiltinCandidate(bound));
+                Ok(())
             }
             Ok(ParameterBuiltin) => { Ok(()) }
             Ok(AmbiguousBuiltin) => { Ok(candidates.ambiguous = true) }
@@ -1539,8 +1527,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                candidate.repr(self.tcx()));
 
         match candidate {
-            // FIXME -- see assemble_builtin_bound_candidates()
-            BuiltinCandidate(_) |
+            BuiltinCandidate(builtin_bound) => {
+                Ok(VtableBuiltin(
+                    try!(self.confirm_builtin_candidate(obligation, builtin_bound))))
+            }
+
             ErrorCandidate => {
                 Ok(VtableBuiltin(VtableBuiltinData { nested: VecPerParamSpace::empty() }))
             }
@@ -1590,8 +1581,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         match try!(self.builtin_bound(bound, obligation.self_ty())) {
             If(nested) => Ok(self.vtable_builtin_data(obligation, bound, nested)),
-            AmbiguousBuiltin |
-            ParameterBuiltin => {
+            AmbiguousBuiltin | ParameterBuiltin => {
                 self.tcx().sess.span_bug(
                     obligation.cause.span,
                     format!("builtin bound for {} was ambig",
diff --git a/src/librustc_trans/trans/base.rs b/src/librustc_trans/trans/base.rs
index 71439f5887b..23072dee3b6 100644
--- a/src/librustc_trans/trans/base.rs
+++ b/src/librustc_trans/trans/base.rs
@@ -965,7 +965,7 @@ pub fn trans_external_path<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 
 pub fn invoke<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                           llfn: ValueRef,
-                          llargs: Vec<ValueRef> ,
+                          llargs: &[ValueRef],
                           fn_ty: Ty<'tcx>,
                           call_info: Option<NodeInfo>,
                           // FIXME(15064) is_lang_item is a horrible hack, please remove it
diff --git a/src/librustc_trans/trans/callee.rs b/src/librustc_trans/trans/callee.rs
index 80a17465d78..50d2f885afa 100644
--- a/src/librustc_trans/trans/callee.rs
+++ b/src/librustc_trans/trans/callee.rs
@@ -808,7 +808,7 @@ pub fn trans_call_inner<'a, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         // Invoke the actual rust fn and update bcx/llresult.
         let (llret, b) = base::invoke(bcx,
                                       llfn,
-                                      llargs,
+                                      llargs[],
                                       callee_ty,
                                       call_info,
                                       dest.is_none());
diff --git a/src/librustc_trans/trans/glue.rs b/src/librustc_trans/trans/glue.rs
index 4ed79837896..fbaf1e65810 100644
--- a/src/librustc_trans/trans/glue.rs
+++ b/src/librustc_trans/trans/glue.rs
@@ -291,7 +291,7 @@ fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         let dtor_ty = ty::mk_ctor_fn(bcx.tcx(),
                                      &[get_drop_glue_type(bcx.ccx(), t)],
                                      ty::mk_nil(bcx.tcx()));
-        let (_, variant_cx) = invoke(variant_cx, dtor_addr, args, dtor_ty, None, false);
+        let (_, variant_cx) = invoke(variant_cx, dtor_addr, args[], dtor_ty, None, false);
 
         variant_cx.fcx.pop_and_trans_custom_cleanup_scope(variant_cx, field_scope);
         variant_cx
diff --git a/src/test/compile-fail/comm-not-freeze-receiver.rs b/src/test/compile-fail/comm-not-freeze-receiver.rs
new file mode 100644
index 00000000000..8cb4b6328c4
--- /dev/null
+++ b/src/test/compile-fail/comm-not-freeze-receiver.rs
@@ -0,0 +1,15 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn test<T: Sync>() {}
+
+fn main() {
+    test::<Receiver<int>>();   //~ ERROR: `core::kinds::Sync` is not implemented
+}
diff --git a/src/test/compile-fail/comm-not-freeze.rs b/src/test/compile-fail/comm-not-freeze.rs
index b6277a3e2bd..8c17895eb8a 100644
--- a/src/test/compile-fail/comm-not-freeze.rs
+++ b/src/test/compile-fail/comm-not-freeze.rs
@@ -11,7 +11,5 @@
 fn test<T: Sync>() {}
 
 fn main() {
-    test::<Sender<int>>();        //~ ERROR: `core::kinds::Sync` is not implemented
-    test::<Receiver<int>>();        //~ ERROR: `core::kinds::Sync` is not implemented
-    test::<Sender<int>>();  //~ ERROR: `core::kinds::Sync` is not implemented
+    test::<Sender<int>>();     //~ ERROR: `core::kinds::Sync` is not implemented
 }
diff --git a/src/test/compile-fail/dst-object-from-unsized-type.rs b/src/test/compile-fail/dst-object-from-unsized-type.rs
index e40cc342c0b..99c63c3c6e9 100644
--- a/src/test/compile-fail/dst-object-from-unsized-type.rs
+++ b/src/test/compile-fail/dst-object-from-unsized-type.rs
@@ -13,18 +13,24 @@
 trait Foo for Sized? {}
 impl Foo for str {}
 
-fn test<Sized? T: Foo>(t: &T) {
+fn test1<Sized? T: Foo>(t: &T) {
     let u: &Foo = t;
     //~^ ERROR `core::kinds::Sized` is not implemented for the type `T`
+}
 
+fn test2<Sized? T: Foo>(t: &T) {
     let v: &Foo = t as &Foo;
     //~^ ERROR `core::kinds::Sized` is not implemented for the type `T`
 }
 
-fn main() {
+fn test3() {
     let _: &[&Foo] = &["hi"];
     //~^ ERROR `core::kinds::Sized` is not implemented for the type `str`
+}
 
+fn test4() {
     let _: &Foo = "hi" as &Foo;
     //~^ ERROR `core::kinds::Sized` is not implemented for the type `str`
 }
+
+fn main() { }
diff --git a/src/test/compile-fail/issue-5883.rs b/src/test/compile-fail/issue-5883.rs
index 96088052e91..e6ac30139c3 100644
--- a/src/test/compile-fail/issue-5883.rs
+++ b/src/test/compile-fail/issue-5883.rs
@@ -18,7 +18,6 @@ fn new_struct(r: A+'static)
     -> Struct { //~^  ERROR the trait `core::kinds::Sized` is not implemented
     //~^ ERROR the trait `core::kinds::Sized` is not implemented
     Struct { r: r }
-    //~^ ERROR the trait `core::kinds::Sized` is not implemented
 }
 
 trait Curve {}
diff --git a/src/test/compile-fail/issue-7013.rs b/src/test/compile-fail/issue-7013.rs
index 3d16ff0a3fa..bef8ca6b86c 100644
--- a/src/test/compile-fail/issue-7013.rs
+++ b/src/test/compile-fail/issue-7013.rs
@@ -32,5 +32,5 @@ struct A {
 
 fn main() {
     let a = A {v: box B{v: None} as Box<Foo+Send>};
-    //~^ ERROR the trait `core::kinds::Send` is not implemented for the type `B`
+    //~^ ERROR the trait `core::kinds::Send` is not implemented
 }
diff --git a/src/test/compile-fail/issue-8727.rs b/src/test/compile-fail/issue-8727.rs
index e2790eb7b39..d1a86d334cb 100644
--- a/src/test/compile-fail/issue-8727.rs
+++ b/src/test/compile-fail/issue-8727.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// error-pattern:reached the recursion limit during monomorphization
+
 // Verify the compiler fails with an error on infinite function
 // recursions.
 
-
 struct Data(Box<Option<Data>>);
 
 fn generic<T>( _ : Vec<(Data,T)> ) {
-    //~^ ERROR reached the recursion limit during monomorphization
     let rec : Vec<(Data,(bool,T))> = Vec::new();
     generic( rec );
 }
diff --git a/src/test/compile-fail/kindck-copy.rs b/src/test/compile-fail/kindck-copy.rs
index 202529c30b3..f0c4a4243ac 100644
--- a/src/test/compile-fail/kindck-copy.rs
+++ b/src/test/compile-fail/kindck-copy.rs
@@ -22,7 +22,7 @@ struct MyStruct {
 }
 
 struct MyNoncopyStruct {
-    x: Box<int>,
+    x: Box<char>,
 }
 
 fn test<'a,T,U:Copy>(_: &'a int) {
diff --git a/src/test/compile-fail/kindck-destructor-owned.rs b/src/test/compile-fail/kindck-destructor-owned.rs
index 26b0c5503e3..1a82a2b3832 100644
--- a/src/test/compile-fail/kindck-destructor-owned.rs
+++ b/src/test/compile-fail/kindck-destructor-owned.rs
@@ -16,7 +16,7 @@ struct Foo {
 }
 
 impl Drop for Foo {
-//~^ ERROR the trait `core::kinds::Send` is not implemented for the type `Foo`
+//~^ ERROR the trait `core::kinds::Send` is not implemented
 //~^^ NOTE cannot implement a destructor on a structure or enumeration that does not satisfy Send
     fn drop(&mut self) {
     }
diff --git a/src/test/compile-fail/kindck-impl-type-params.rs b/src/test/compile-fail/kindck-impl-type-params.rs
index c92887965c0..a430fe72333 100644
--- a/src/test/compile-fail/kindck-impl-type-params.rs
+++ b/src/test/compile-fail/kindck-impl-type-params.rs
@@ -22,6 +22,10 @@ fn f<T>(val: T) {
     let a = &t as &Gettable<T>;
     //~^ ERROR the trait `core::kinds::Send` is not implemented
     //~^^ ERROR the trait `core::kinds::Copy` is not implemented
+}
+
+fn g<T>(val: T) {
+    let t: S<T> = S;
     let a: &Gettable<T> = &t;
     //~^ ERROR the trait `core::kinds::Send` is not implemented
     //~^^ ERROR the trait `core::kinds::Copy` is not implemented
@@ -30,9 +34,15 @@ fn f<T>(val: T) {
 fn foo<'a>() {
     let t: S<&'a int> = S;
     let a = &t as &Gettable<&'a int>;
+}
+
+fn foo2<'a>() {
     let t: Box<S<String>> = box S;
     let a = t as Box<Gettable<String>>;
     //~^ ERROR the trait `core::kinds::Copy` is not implemented
+}
+
+fn foo3<'a>() {
     let t: Box<S<String>> = box S;
     let a: Box<Gettable<String>> = t;
     //~^ ERROR the trait `core::kinds::Copy` is not implemented
diff --git a/src/test/compile-fail/kindck-nonsendable-1.rs b/src/test/compile-fail/kindck-nonsendable-1.rs
index 6ca3f0174bb..d694fd2c795 100644
--- a/src/test/compile-fail/kindck-nonsendable-1.rs
+++ b/src/test/compile-fail/kindck-nonsendable-1.rs
@@ -13,10 +13,14 @@ use std::rc::Rc;
 
 fn foo(_x: Rc<uint>) {}
 
-fn main() {
+fn bar() {
     let x = Rc::new(3u);
     let _: proc():Send = proc() foo(x); //~ ERROR `core::kinds::Send` is not implemented
-    let _: proc():Send = proc() foo(x); //~ ERROR `core::kinds::Send` is not implemented
-    let _: proc():Send = proc() foo(x); //~ ERROR `core::kinds::Send` is not implemented
+}
+
+fn bar2() {
+    let x = Rc::new(3u);
     let _: proc() = proc() foo(x);
 }
+
+fn main() { }
diff --git a/src/test/compile-fail/unsendable-class.rs b/src/test/compile-fail/unsendable-class.rs
index 102cb636550..d988a245700 100644
--- a/src/test/compile-fail/unsendable-class.rs
+++ b/src/test/compile-fail/unsendable-class.rs
@@ -29,5 +29,5 @@ fn foo(i:int, j: Rc<String>) -> foo {
 fn main() {
   let cat = "kitty".to_string();
   let (tx, _) = channel(); //~ ERROR `core::kinds::Send` is not implemented
-  tx.send(foo(42, Rc::new(cat))); //~ ERROR `core::kinds::Send` is not implemented
+  tx.send(foo(42, Rc::new(cat)));
 }
diff --git a/src/test/compile-fail/unsized-enum.rs b/src/test/compile-fail/unsized-enum.rs
index edef3ae6492..0462a2025d2 100644
--- a/src/test/compile-fail/unsized-enum.rs
+++ b/src/test/compile-fail/unsized-enum.rs
@@ -8,14 +8,22 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-enum Foo<T> { FooSome(T), FooNone }
 
-fn bar<T: Sized>() { }
-fn foo<Sized? T>() { bar::<Foo<T>>() }
+fn is_sized<T:Sized>() { }
+fn not_sized<Sized? T>() { }
+
+enum Foo<U> { FooSome(U), FooNone }
+fn foo1<T>() { not_sized::<Foo<T>>() } // Hunky dory.
+fn foo2<Sized? T>() { not_sized::<Foo<T>>() }
 //~^ ERROR the trait `core::kinds::Sized` is not implemented
-//~^^ ERROR the trait `core::kinds::Sized` is not implemented
 //
-// One error is for T being provided to Foo<T>, the other is
-// for Foo<T> being provided to bar.
+// Not OK: `T` is not sized.
+
+enum Bar<Sized? U> { BarSome(U), BarNone }
+fn bar1<Sized? T>() { not_sized::<Bar<T>>() }
+fn bar2<Sized? T>() { is_sized::<Bar<T>>() }
+//~^ ERROR the trait `core::kinds::Sized` is not implemented
+//
+// Not OK: `Bar<T>` is not sized, but it should be.
 
 fn main() { }
diff --git a/src/test/compile-fail/unsized-struct.rs b/src/test/compile-fail/unsized-struct.rs
index 58aba1a2646..db2e9cb9328 100644
--- a/src/test/compile-fail/unsized-struct.rs
+++ b/src/test/compile-fail/unsized-struct.rs
@@ -8,13 +8,22 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-struct Foo<T> { data: T }
 
-fn bar<T: Sized>() { }
-fn foo<Sized? T>() { bar::<Foo<T>>() }
+fn is_sized<T:Sized>() { }
+fn not_sized<Sized? T>() { }
+
+struct Foo<T> { data: T }
+fn foo1<T>() { not_sized::<Foo<T>>() } // Hunky dory.
+fn foo2<Sized? T>() { not_sized::<Foo<T>>() }
 //~^ ERROR the trait `core::kinds::Sized` is not implemented
-//~^^ ERROR the trait `core::kinds::Sized` is not implemented
-// One error is for the T in Foo<T>, the other is for Foo<T> as a value
-// for bar's type parameter.
+//
+// Not OK: `T` is not sized.
+
+struct Bar<Sized? T> { data: T }
+fn bar1<Sized? T>() { not_sized::<Bar<T>>() }
+fn bar2<Sized? T>() { is_sized::<Bar<T>>() }
+//~^ ERROR the trait `core::kinds::Sized` is not implemented
+//
+// Not OK: `Bar<T>` is not sized, but it should be.
 
 fn main() { }
diff --git a/src/test/compile-fail/unsized3.rs b/src/test/compile-fail/unsized3.rs
index fba1237340f..0a75240f2d8 100644
--- a/src/test/compile-fail/unsized3.rs
+++ b/src/test/compile-fail/unsized3.rs
@@ -57,6 +57,9 @@ fn f8<Sized? X>(x1: &S<X>, x2: &S<X>) {
 fn f9<Sized? X>(x1: Box<S<X>>, x2: Box<E<X>>) {
     f5(&(*x1, 34i));
     //~^ ERROR the trait `core::kinds::Sized` is not implemented
+}
+
+fn f10<Sized? X>(x1: Box<S<X>>, x2: Box<E<X>>) {
     f5(&(32i, *x2));
     //~^ ERROR the trait `core::kinds::Sized` is not implemented
 }
diff --git a/src/test/compile-fail/unsized5.rs b/src/test/compile-fail/unsized5.rs
index 2f1eb35a426..d9d7a86889f 100644
--- a/src/test/compile-fail/unsized5.rs
+++ b/src/test/compile-fail/unsized5.rs
@@ -29,6 +29,8 @@ struct S4 {
 }
 enum E<Sized? X> {
     V1(X, int), //~ERROR `core::kinds::Sized` is not implemented
+}
+enum F<Sized? X> {
     V2{f1: X, f: int}, //~ERROR `core::kinds::Sized` is not implemented
 }