Fix a bug in the opt-in-copy work: it was failing to liberate the regions...

Fix a bug in the opt-in-copy work: it was failing to liberate the regions bound in the impl before searching for `Copy` implements for all fields, leading to problems in the "copyability check". Basically the copyability check would wind up looking for an impl of `for<'tcx> Foo<&'tcx T>`. The impl that exists however is `impl<T> Copy for Foo<T>` and the current rules do not consider that a match (something I would like to revise in a later PR).

src/librustc_typeck/coherence/mod.rs

@@ -18,6 +18,7 @@
 
 use metadata::csearch::{each_impl, get_impl_trait};
 use metadata::csearch;
+use middle::region;
 use middle::subst::{mod, Subst};
 use middle::ty::{ImplContainer, ImplOrTraitItemId, MethodTraitItemId};
 use middle::ty::{ParameterEnvironment, TypeTraitItemId, lookup_item_type};
@@ -26,8 +27,6 @@
 use middle::ty::{ty_rptr, ty_struct, ty_trait, ty_tup};
 use middle::ty::{ty_str, ty_vec, ty_float, ty_infer, ty_int, ty_open};
 use middle::ty::{ty_uint, ty_unboxed_closure, ty_uniq, ty_bare_fn};
-use middle::ty::{ty_closure};
-use middle::subst::Subst;
 use middle::ty;
 use CrateCtxt;
 use middle::infer::combine::Combine;
@@ -472,6 +471,17 @@ fn check_implementations_of_copy(&self) {
                                                            impl_did.node);
             let self_type = self_type.ty.subst(tcx, &param_env.free_substs);
 
+            // the self-type may have late-bound regions bound in the
+            // impl; liberate them.
+            let item_scope = region::CodeExtent::from_node_id(impl_did.node);
+            let self_type =
+                ty::liberate_late_bound_regions(tcx,
+                                                item_scope,
+                                                &ty::bind(self_type)).value;
+
+            debug!("can_type_implement_copy(self_type={})",
+                   self_type.repr(tcx));
+
             match ty::can_type_implement_copy(tcx, self_type, &param_env) {
                 Ok(()) => {}
                 Err(ty::FieldDoesNotImplementCopy(name)) => {

src/test/run-pass/hrtb-opt-in-copy.rs

+// Copyright 2014 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.
+
+// Test that we handle binder levels correctly when checking whether a
+// type can implement `Copy`. In particular, we had a bug where we failed to
+// liberate the late-bound regions from the impl, and thus wound up
+// searching for an impl of `for<'tcx> Foo<&'tcx T>`. The impl that
+// exists however is `impl<T> Copy for Foo<T>` and the current rules
+// did not consider that a match (something I would like to revise in
+// a later PR).
+
+#![allow(dead_code)]
+
+use std::kinds::marker;
+
+#[deriving(Copy)]
+struct Foo<T> { x: T }
+
+type Ty<'tcx> = &'tcx TyS<'tcx>;
+
+enum TyS<'tcx> {
+    Boop(marker::InvariantLifetime<'tcx>)
+}
+
+enum Bar<'tcx> {
+    Baz(Foo<Ty<'tcx>>)
+}
+
+impl<'tcx> Copy for Bar<'tcx> { }
+
+fn main() { }