diff --git a/src/libcore/borrow.rs b/src/libcore/borrow.rs
index 7e4d73d598d8d..ebb4bd88cf139 100644
--- a/src/libcore/borrow.rs
+++ b/src/libcore/borrow.rs
@@ -53,12 +53,14 @@ use option::Option;
 use self::Cow::*;
 
 /// A trait for borrowing data.
+#[old_orphan_check]
 pub trait BorrowFrom<Sized? Owned> for Sized? {
     /// Immutably borrow from an owned value.
     fn borrow_from(owned: &Owned) -> &Self;
 }
 
 /// A trait for mutably borrowing data.
+#[old_orphan_check]
 pub trait BorrowFromMut<Sized? Owned> for Sized? : BorrowFrom<Owned> {
     /// Mutably borrow from an owned value.
     fn borrow_from_mut(owned: &mut Owned) -> &mut Self;
@@ -91,6 +93,7 @@ impl<'a, T, Sized? B> BorrowFrom<Cow<'a, T, B>> for B where B: ToOwned<T> {
 }
 
 /// Trait for moving into a `Cow`
+#[old_orphan_check]
 pub trait IntoCow<'a, T, Sized? B> {
     /// Moves `self` into `Cow`
     fn into_cow(self) -> Cow<'a, T, B>;
@@ -103,6 +106,7 @@ impl<'a, T, Sized? B> IntoCow<'a, T, B> for Cow<'a, T, B> where B: ToOwned<T> {
 }
 
 /// A generalization of Clone to borrowed data.
+#[old_orphan_check]
 pub trait ToOwned<Owned> for Sized?: BorrowFrom<Owned> {
     /// Create owned data from borrowed data, usually by copying.
     fn to_owned(&self) -> Owned;
diff --git a/src/libcore/cmp.rs b/src/libcore/cmp.rs
index 13f9f5ccee916..90ff174c2bdbd 100644
--- a/src/libcore/cmp.rs
+++ b/src/libcore/cmp.rs
@@ -69,6 +69,7 @@ use option::Option::{self, Some, None};
 /// only if `a != b`.
 #[lang="eq"]
 #[stable]
+#[old_orphan_check]
 pub trait PartialEq<Sized? Rhs = Self> for Sized? {
     /// This method tests for `self` and `other` values to be equal, and is used by `==`.
     #[stable]
diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index 8f03f8821285a..cf5ca5956f4b3 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -670,6 +670,9 @@ impl LintPass for UnusedAttributes {
             "must_use",
             "stable",
             "unstable",
+
+            // FIXME: #19470 this shouldn't be needed forever
+            "old_orphan_check",
         ];
 
         static CRATE_ATTRS: &'static [&'static str] = &[
diff --git a/src/librustc/middle/traits/coherence.rs b/src/librustc/middle/traits/coherence.rs
index e6805cddae05a..96b94ab298ad0 100644
--- a/src/librustc/middle/traits/coherence.rs
+++ b/src/librustc/middle/traits/coherence.rs
@@ -14,7 +14,7 @@ use super::SelectionContext;
 use super::{Obligation, ObligationCause};
 use super::util;
 
-use middle::subst::Subst;
+use middle::subst::{Subst};
 use middle::ty::{self, Ty};
 use middle::infer::InferCtxt;
 use std::collections::HashSet;
@@ -53,20 +53,20 @@ pub fn impl_can_satisfy(infcx: &InferCtxt,
 }
 
 #[allow(missing_copy_implementations)]
-pub enum OrphanCheckErr {
+pub enum OrphanCheckErr<'tcx> {
     NoLocalInputType,
-    UncoveredTypeParameter(ty::ParamTy),
+    UncoveredTy(Ty<'tcx>),
 }
 
 /// Checks the coherence orphan rules. `impl_def_id` should be the
 /// def-id of a trait impl. To pass, either the trait must be local, or else
 /// two conditions must be satisfied:
 ///
-/// 1. At least one of the input types must involve a local type.
-/// 2. All type parameters must be covered by a local type.
-pub fn orphan_check(tcx: &ty::ctxt,
-                    impl_def_id: ast::DefId)
-                    -> Result<(), OrphanCheckErr>
+/// 1. All type parameters in `Self` must be "covered" by some local type constructor.
+/// 2. Some local type must appear in `Self`.
+pub fn orphan_check<'tcx>(tcx: &ty::ctxt<'tcx>,
+                          impl_def_id: ast::DefId)
+                          -> Result<(), OrphanCheckErr<'tcx>>
 {
     debug!("impl_is_local({})", impl_def_id.repr(tcx));
 
@@ -82,31 +82,21 @@ pub fn orphan_check(tcx: &ty::ctxt,
         return Ok(());
     }
 
-    // Check condition 1: at least one type must be local.
-    if !trait_ref.input_types().iter().any(|&t| ty_reaches_local(tcx, t)) {
-        return Err(OrphanCheckErr::NoLocalInputType);
+    // Otherwise, check that (1) all type parameters are covered.
+    let covered_params = type_parameters_covered_by_ty(tcx, trait_ref.self_ty());
+    let all_params = type_parameters_reachable_from_ty(trait_ref.self_ty());
+    for &param in all_params.difference(&covered_params) {
+        return Err(OrphanCheckErr::UncoveredTy(param));
     }
 
-    // Check condition 2: type parameters must be "covered" by a local type.
-    let covered_params: HashSet<_> =
-        trait_ref.input_types().iter()
-                               .flat_map(|&t| type_parameters_covered_by_ty(tcx, t).into_iter())
-                               .collect();
-    let all_params: HashSet<_> =
-        trait_ref.input_types().iter()
-                               .flat_map(|&t| type_parameters_reachable_from_ty(t).into_iter())
-                               .collect();
-    for &param in all_params.difference(&covered_params) {
-        return Err(OrphanCheckErr::UncoveredTypeParameter(param));
+    // And (2) some local type appears.
+    if !trait_ref.self_ty().walk().any(|t| ty_is_local_constructor(tcx, t)) {
+        return Err(OrphanCheckErr::NoLocalInputType);
     }
 
     return Ok(());
 }
 
-fn ty_reaches_local<'tcx>(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> bool {
-    ty.walk().any(|t| ty_is_local_constructor(tcx, t))
-}
-
 fn ty_is_local_constructor<'tcx>(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> bool {
     debug!("ty_is_local_constructor({})", ty.repr(tcx));
 
@@ -154,8 +144,8 @@ fn ty_is_local_constructor<'tcx>(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> bool {
 }
 
 fn type_parameters_covered_by_ty<'tcx>(tcx: &ty::ctxt<'tcx>,
-                                 ty: Ty<'tcx>)
-                                 -> HashSet<ty::ParamTy>
+                                       ty: Ty<'tcx>)
+                                       -> HashSet<Ty<'tcx>>
 {
     if ty_is_local_constructor(tcx, ty) {
         type_parameters_reachable_from_ty(ty)
@@ -165,14 +155,14 @@ fn type_parameters_covered_by_ty<'tcx>(tcx: &ty::ctxt<'tcx>,
 }
 
 /// All type parameters reachable from `ty`
-fn type_parameters_reachable_from_ty<'tcx>(ty: Ty<'tcx>) -> HashSet<ty::ParamTy> {
+fn type_parameters_reachable_from_ty<'tcx>(ty: Ty<'tcx>) -> HashSet<Ty<'tcx>> {
     ty.walk()
-        .filter_map(|t| {
+        .filter(|&t| {
             match t.sty {
-                ty::ty_param(ref param_ty) => Some(param_ty.clone()),
-                _ => None,
+                // FIXME(#20590) straighten story about projection types
+                ty::ty_projection(..) | ty::ty_param(..) => true,
+                _ => false,
             }
         })
         .collect()
 }
-
diff --git a/src/librustc_typeck/check/callee.rs b/src/librustc_typeck/check/callee.rs
index 153c6463fbebb..0bc76e1baab84 100644
--- a/src/librustc_typeck/check/callee.rs
+++ b/src/librustc_typeck/check/callee.rs
@@ -22,7 +22,7 @@ use super::TupleArgumentsFlag;
 use super::write_call;
 
 use middle::infer;
-use middle::ty::{mod, Ty};
+use middle::ty::{self, Ty};
 use syntax::ast;
 use syntax::codemap::Span;
 use syntax::parse::token;
diff --git a/src/librustc_typeck/coherence/orphan.rs b/src/librustc_typeck/coherence/orphan.rs
index 1da49799712bd..dc22fd597e689 100644
--- a/src/librustc_typeck/coherence/orphan.rs
+++ b/src/librustc_typeck/coherence/orphan.rs
@@ -72,20 +72,30 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
             ast::ItemImpl(_, _, Some(_), _, _) => {
                 // "Trait" impl
                 debug!("coherence2::orphan check: trait impl {}", item.repr(self.tcx));
+                let trait_def_id = ty::impl_trait_ref(self.tcx, def_id).unwrap().def_id;
                 match traits::orphan_check(self.tcx, def_id) {
                     Ok(()) => { }
                     Err(traits::OrphanCheckErr::NoLocalInputType) => {
-                        span_err!(self.tcx.sess, item.span, E0117,
-                                  "cannot provide an extension implementation \
-                                   where both trait and type are not defined in this crate");
+                        if !ty::has_attr(self.tcx, trait_def_id, "old_orphan_check") {
+                            let self_ty = ty::lookup_item_type(self.tcx, def_id).ty;
+                            span_err!(
+                                self.tcx.sess, item.span, E0117,
+                                "the type `{}` does not reference any \
+                                 types defined in this crate; \
+                                 only traits defined in the current crate can be \
+                                 implemented for arbitrary types",
+                                self_ty.user_string(self.tcx));
+                        }
                     }
-                    Err(traits::OrphanCheckErr::UncoveredTypeParameter(param_ty)) => {
-                        if !self.tcx.sess.features.borrow().old_orphan_check {
+                    Err(traits::OrphanCheckErr::UncoveredTy(param_ty)) => {
+                        if !ty::has_attr(self.tcx, trait_def_id, "old_orphan_check") {
                             self.tcx.sess.span_err(
                                 item.span,
-                                format!("type parameter `{}` must also appear as a type parameter \
-                                         of some type defined within this crate",
-                                        param_ty.user_string(self.tcx)).as_slice());
+                                format!(
+                                    "type parameter `{}` is not constrained by any local type; \
+                                     only traits defined in the current crate can be implemented \
+                                     for a type parameter",
+                                    param_ty.user_string(self.tcx)).as_slice());
                             self.tcx.sess.span_note(
                                 item.span,
                                 format!("for a limited time, you can add \
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index f75873ac1c0f7..f08c40ff0997b 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -301,6 +301,14 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                                        removed in the future");
                 }
 
+                if attr::contains_name(i.attrs[],
+                                       "old_orphan_check") {
+                    self.gate_feature(
+                        "old_orphan_check",
+                        i.span,
+                        "the new orphan check rules will eventually be strictly enforced");
+                }
+
                 for item in items.iter() {
                     match *item {
                         ast::MethodImplItem(_) => {}
diff --git a/src/test/compile-fail/coherence-all-remote.rs b/src/test/compile-fail/coherence-all-remote.rs
index 67d96aa95a6a2..d88b8751ea7b0 100644
--- a/src/test/compile-fail/coherence-all-remote.rs
+++ b/src/test/compile-fail/coherence-all-remote.rs
@@ -14,6 +14,6 @@ extern crate "coherence-lib" as lib;
 use lib::Remote;
 
 impl<T> Remote for int { }
-//~^ ERROR cannot provide an extension implementation
+//~^ ERROR E0117
 
 fn main() { }
diff --git a/src/test/run-pass/coherence-bigint-int.rs b/src/test/compile-fail/coherence-bigint-int.rs
similarity index 92%
rename from src/test/run-pass/coherence-bigint-int.rs
rename to src/test/compile-fail/coherence-bigint-int.rs
index 1e90453980f86..b4917d0c29f37 100644
--- a/src/test/run-pass/coherence-bigint-int.rs
+++ b/src/test/compile-fail/coherence-bigint-int.rs
@@ -15,6 +15,6 @@ use lib::Remote1;
 
 pub struct BigInt;
 
-impl Remote1<BigInt> for int { }
+impl Remote1<BigInt> for int { } //~ ERROR E0117
 
 fn main() { }
diff --git a/src/test/compile-fail/coherence-bigint-param.rs b/src/test/compile-fail/coherence-bigint-param.rs
index a04dfd36c98f1..b8e48436a4143 100644
--- a/src/test/compile-fail/coherence-bigint-param.rs
+++ b/src/test/compile-fail/coherence-bigint-param.rs
@@ -16,6 +16,6 @@ use lib::Remote1;
 pub struct BigInt;
 
 impl<T> Remote1<BigInt> for T { }
-//~^ ERROR type parameter `T` must also appear
+//~^ ERROR type parameter `T` is not constrained
 
 fn main() { }
diff --git a/src/test/run-pass/coherence-bigint-vecint.rs b/src/test/compile-fail/coherence-bigint-vecint.rs
similarity index 91%
rename from src/test/run-pass/coherence-bigint-vecint.rs
rename to src/test/compile-fail/coherence-bigint-vecint.rs
index b100455eb339c..de4e656110f29 100644
--- a/src/test/run-pass/coherence-bigint-vecint.rs
+++ b/src/test/compile-fail/coherence-bigint-vecint.rs
@@ -15,6 +15,6 @@ use lib::Remote1;
 
 pub struct BigInt;
 
-impl Remote1<BigInt> for Vec<int> { }
+impl Remote1<BigInt> for Vec<int> { } //~ ERROR E0117
 
 fn main() { }
diff --git a/src/test/compile-fail/coherence-cross-crate-conflict.rs b/src/test/compile-fail/coherence-cross-crate-conflict.rs
index 99446be43acaa..8bdd5c58f3199 100644
--- a/src/test/compile-fail/coherence-cross-crate-conflict.rs
+++ b/src/test/compile-fail/coherence-cross-crate-conflict.rs
@@ -16,7 +16,7 @@ extern crate trait_impl_conflict;
 use trait_impl_conflict::Foo;
 
 impl<A> Foo for A {
-    //~^ ERROR E0117
+    //~^ ERROR type parameter `A` is not constrained
     //~^^ ERROR E0119
 }
 
diff --git a/src/test/compile-fail/coherence-lone-type-parameter.rs b/src/test/compile-fail/coherence-lone-type-parameter.rs
index 0223dacd8eca0..917438722de4e 100644
--- a/src/test/compile-fail/coherence-lone-type-parameter.rs
+++ b/src/test/compile-fail/coherence-lone-type-parameter.rs
@@ -13,6 +13,6 @@
 extern crate "coherence-lib" as lib;
 use lib::Remote;
 
-impl<T> Remote for T { } //~ ERROR E0117
+impl<T> Remote for T { } //~ ERROR type parameter `T` is not constrained
 
 fn main() { }
diff --git a/src/test/compile-fail/coherence-orphan.rs b/src/test/compile-fail/coherence-orphan.rs
index c44b0da5b154f..30a382c143dab 100644
--- a/src/test/compile-fail/coherence-orphan.rs
+++ b/src/test/compile-fail/coherence-orphan.rs
@@ -18,7 +18,7 @@ struct TheType;
 
 impl TheTrait<uint> for int { } //~ ERROR E0117
 
-impl TheTrait<TheType> for int { }
+impl TheTrait<TheType> for int { } //~ ERROR E0117
 
 impl TheTrait<int> for TheType { }
 
diff --git a/src/test/compile-fail/coherence-overlapping-pairs.rs b/src/test/compile-fail/coherence-overlapping-pairs.rs
index d42bd529b6665..9354e66af0d81 100644
--- a/src/test/compile-fail/coherence-overlapping-pairs.rs
+++ b/src/test/compile-fail/coherence-overlapping-pairs.rs
@@ -16,6 +16,6 @@ use lib::Remote;
 struct Foo;
 
 impl<T> Remote for lib::Pair<T,Foo> { }
-//~^ ERROR type parameter `T` must also appear
+//~^ ERROR type parameter `T` is not constrained
 
 fn main() { }
diff --git a/src/test/compile-fail/coherence-pair-covered-uncovered.rs b/src/test/compile-fail/coherence-pair-covered-uncovered.rs
index 09895ec11db10..92a07b3585292 100644
--- a/src/test/compile-fail/coherence-pair-covered-uncovered.rs
+++ b/src/test/compile-fail/coherence-pair-covered-uncovered.rs
@@ -16,6 +16,6 @@ use lib::{Remote, Pair};
 struct Local<T>(T);
 
 impl<T,U> Remote for Pair<T,Local<U>> { }
-//~^ ERROR type parameter `T` must also appear
+//~^ ERROR type parameter `T` is not constrained
 
 fn main() { }
diff --git a/src/test/compile-fail/drop-on-non-struct.rs b/src/test/compile-fail/drop-on-non-struct.rs
index 8304afa1141ee..238700254b8fd 100644
--- a/src/test/compile-fail/drop-on-non-struct.rs
+++ b/src/test/compile-fail/drop-on-non-struct.rs
@@ -10,7 +10,7 @@
 
 impl Drop for int {
     //~^ ERROR the Drop trait may only be implemented on structures
-    //~^^ ERROR cannot provide an extension implementation
+    //~^^ ERROR E0117
     fn drop(&mut self) {
         println!("kaboom");
     }
diff --git a/src/test/compile-fail/coherence-iterator-vec-any-elem.rs b/src/test/run-pass/coherence-iterator-vec-any-elem.rs
similarity index 92%
rename from src/test/compile-fail/coherence-iterator-vec-any-elem.rs
rename to src/test/run-pass/coherence-iterator-vec-any-elem.rs
index 2ed7a6db7ae1c..6dc2ff4588b67 100644
--- a/src/test/compile-fail/coherence-iterator-vec-any-elem.rs
+++ b/src/test/run-pass/coherence-iterator-vec-any-elem.rs
@@ -16,6 +16,5 @@ use lib::Remote1;
 struct Foo<T>(T);
 
 impl<T,U> Remote1<U> for Foo<T> { }
-//~^ ERROR type parameter `U` must also appear
 
 fn main() { }