//! See `doc.rs` for high-level documentation
+use super::Normalized;
use super::SelectionContext;
-use super::{Obligation, ObligationCause};
+use super::{ObligationCause};
+use super::PredicateObligation;
use super::project;
use super::util;
use middle::subst::{Subst, TypeSpace};
-use middle::ty::{self, Ty};
-use middle::infer::InferCtxt;
+use middle::ty::{self, ToPolyTraitRef, Ty};
+use middle::infer::{self, InferCtxt};
use std::collections::HashSet;
use std::rc::Rc;
use syntax::ast;
use syntax::codemap::DUMMY_SP;
use util::ppaux::Repr;
-pub fn impl_can_satisfy(infcx: &InferCtxt,
- impl1_def_id: ast::DefId,
- impl2_def_id: ast::DefId)
- -> bool
+/// True if there exist types that satisfy both of the two given impls.
+pub fn overlapping_impls(infcx: &InferCtxt,
+ impl1_def_id: ast::DefId,
+ impl2_def_id: ast::DefId)
+ -> bool
{
debug!("impl_can_satisfy(\
impl1_def_id={}, \
impl1_def_id.repr(infcx.tcx),
impl2_def_id.repr(infcx.tcx));
- let param_env = ty::empty_parameter_environment(infcx.tcx);
- let mut selcx = SelectionContext::intercrate(infcx, ¶m_env);
- let cause = ObligationCause::dummy();
-
- // `impl1` provides an implementation of `Foo<X,Y> for Z`.
- let impl1_substs =
- util::fresh_substs_for_impl(infcx, DUMMY_SP, impl1_def_id);
- let impl1_trait_ref =
- (*ty::impl_trait_ref(infcx.tcx, impl1_def_id).unwrap()).subst(infcx.tcx, &impl1_substs);
- let impl1_trait_ref =
- project::normalize(&mut selcx, cause.clone(), &impl1_trait_ref);
-
- // Determine whether `impl2` can provide an implementation for those
- // same types.
- let obligation = Obligation::new(cause,
- ty::Binder(ty::TraitPredicate {
- trait_ref: Rc::new(impl1_trait_ref.value),
- }));
- debug!("impl_can_satisfy(obligation={})", obligation.repr(infcx.tcx));
- selcx.evaluate_impl(impl2_def_id, &obligation) &&
- impl1_trait_ref.obligations.iter().all(
- |o| selcx.evaluate_obligation(o))
+ let param_env = &ty::empty_parameter_environment(infcx.tcx);
+ let selcx = &mut SelectionContext::intercrate(infcx, param_env);
+ infcx.probe(|_| {
+ overlap(selcx, impl1_def_id, impl2_def_id) || overlap(selcx, impl2_def_id, impl1_def_id)
+ })
+}
+
+/// Can the types from impl `a` be used to satisfy impl `b`?
+/// (Including all conditions)
+fn overlap(selcx: &mut SelectionContext,
+ a_def_id: ast::DefId,
+ b_def_id: ast::DefId)
+ -> bool
+{
+ let (a_trait_ref, a_obligations) = impl_trait_ref_and_oblig(selcx, a_def_id);
+ let (b_trait_ref, b_obligations) = impl_trait_ref_and_oblig(selcx, b_def_id);
+
+ // Does `a <: b` hold? If not, no overlap.
+ if let Err(_) = infer::mk_sub_poly_trait_refs(selcx.infcx(),
+ true,
+ infer::Misc(DUMMY_SP),
+ a_trait_ref.to_poly_trait_ref(),
+ b_trait_ref.to_poly_trait_ref()) {
+ return false;
+ }
+
+ // Are any of the obligations unsatisfiable? If so, no overlap.
+ a_obligations.iter()
+ .chain(b_obligations.iter())
+ .all(|o| selcx.evaluate_obligation(o))
+}
+
+/// Instantiate fresh variables for all bound parameters of the impl
+/// and return the impl trait ref with those variables substituted.
+fn impl_trait_ref_and_oblig<'a,'tcx>(selcx: &mut SelectionContext<'a,'tcx>,
+ impl_def_id: ast::DefId)
+ -> (Rc<ty::TraitRef<'tcx>>,
+ Vec<PredicateObligation<'tcx>>)
+{
+ let impl_substs =
+ &util::fresh_substs_for_impl(selcx.infcx(), DUMMY_SP, impl_def_id);
+ let impl_trait_ref =
+ ty::impl_trait_ref(selcx.tcx(), impl_def_id).unwrap();
+ let impl_trait_ref =
+ impl_trait_ref.subst(selcx.tcx(), impl_substs);
+ let Normalized { value: impl_trait_ref, obligations: normalization_obligations1 } =
+ project::normalize(selcx, ObligationCause::dummy(), &impl_trait_ref);
+
+ let predicates = ty::lookup_predicates(selcx.tcx(), impl_def_id);
+ let predicates = predicates.instantiate(selcx.tcx(), impl_substs);
+ let Normalized { value: predicates, obligations: normalization_obligations2 } =
+ project::normalize(selcx, ObligationCause::dummy(), &predicates);
+ let impl_obligations =
+ util::predicates_for_generics(selcx.tcx(), ObligationCause::dummy(), 0, &predicates);
+
+ let impl_obligations: Vec<_> =
+ impl_obligations.into_iter()
+ .chain(normalization_obligations1.into_iter())
+ .chain(normalization_obligations2.into_iter())
+ .collect();
+
+ (impl_trait_ref, impl_obligations)
}
pub enum OrphanCheckErr<'tcx> {
pub use self::error_reporting::report_fulfillment_errors;
pub use self::error_reporting::suggest_new_overflow_limit;
pub use self::coherence::orphan_check;
+pub use self::coherence::overlapping_impls;
pub use self::coherence::OrphanCheckErr;
pub use self::fulfill::{FulfillmentContext, RegionObligation};
pub use self::project::MismatchedProjectionTypes;
pub object_ty: Ty<'tcx>,
}
-/// True if there exist types that satisfy both of the two given impls.
-pub fn overlapping_impls(infcx: &InferCtxt,
- impl1_def_id: ast::DefId,
- impl2_def_id: ast::DefId)
- -> bool
-{
- coherence::impl_can_satisfy(infcx, impl1_def_id, impl2_def_id) &&
- coherence::impl_can_satisfy(infcx, impl2_def_id, impl1_def_id)
-}
-
/// Creates predicate obligations from the generic bounds.
pub fn predicates_for_generics<'tcx>(tcx: &ty::ctxt<'tcx>,
cause: ObligationCause<'tcx>,
--- /dev/null
+// Copyright 2015 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 two distinct impls which match subtypes of one another
+// yield coherence errors (or not) depending on the variance.
+
+trait Contravariant {
+ fn foo(&self) { }
+}
+
+impl Contravariant for for<'a,'b> fn(&'a u8, &'b u8) {
+ //~^ ERROR E0119
+}
+
+impl Contravariant for for<'a> fn(&'a u8, &'a u8) {
+}
+
+///////////////////////////////////////////////////////////////////////////
+
+trait Covariant {
+ fn foo(&self) { }
+}
+
+impl Covariant for for<'a,'b> fn(&'a u8, &'b u8) {
+ //~^ ERROR E0119
+}
+
+impl Covariant for for<'a> fn(&'a u8, &'a u8) {
+}
+
+///////////////////////////////////////////////////////////////////////////
+
+trait Invariant {
+ fn foo(&self) -> Self { }
+}
+
+impl Invariant for for<'a,'b> fn(&'a u8, &'b u8) {
+}
+
+impl Invariant for for<'a> fn(&'a u8, &'a u8) {
+}
+
+fn main() { }