use middle::free_region::FreeRegionMap;
use infer::{InferCtxt, GenericKind};
-use traits::FulfillmentContext;
-use ty::{self, Ty, TypeFoldable};
-use ty::outlives::Component;
-use ty::wf;
+use infer::outlives::implied_bounds::ImpliedBound;
+use ty::{self, Ty};
use syntax::ast;
use syntax_pos::Span;
region_bound_pairs: Vec<(ty::Region<'tcx>, GenericKind<'tcx>)>,
}
-/// Implied bounds are region relationships that we deduce
-/// automatically. The idea is that (e.g.) a caller must check that a
-/// function's argument types are well-formed immediately before
-/// calling that fn, and hence the *callee* can assume that its
-/// argument types are well-formed. This may imply certain relationships
-/// between generic parameters. For example:
-///
-/// fn foo<'a,T>(x: &'a T)
-///
-/// can only be called with a `'a` and `T` such that `&'a T` is WF.
-/// For `&'a T` to be WF, `T: 'a` must hold. So we can assume `T: 'a`.
-#[derive(Debug)]
-enum ImpliedBound<'tcx> {
- RegionSubRegion(ty::Region<'tcx>, ty::Region<'tcx>),
- RegionSubParam(ty::Region<'tcx>, ty::ParamTy),
- RegionSubProjection(ty::Region<'tcx>, ty::ProjectionTy<'tcx>),
-}
-
impl<'a, 'gcx: 'tcx, 'tcx: 'a> OutlivesEnvironment<'tcx> {
pub fn new(param_env: ty::ParamEnv<'tcx>) -> Self {
let mut free_region_map = FreeRegionMap::new();
for &ty in fn_sig_tys {
let ty = infcx.resolve_type_vars_if_possible(&ty);
debug!("add_implied_bounds: ty = {}", ty);
- let implied_bounds = self.implied_bounds(infcx, body_id, ty, span);
+ let implied_bounds = infcx.implied_bounds(self.param_env, body_id, ty, span);
// But also record other relationships, such as `T:'x`,
// that don't go into the free-region-map but which we use
}
}
}
-
- /// Compute the implied bounds that a callee/impl can assume based on
- /// the fact that caller/projector has ensured that `ty` is WF. See
- /// the `ImpliedBound` type for more details.
- fn implied_bounds(
- &mut self,
- infcx: &InferCtxt<'a, 'gcx, 'tcx>,
- body_id: ast::NodeId,
- ty: Ty<'tcx>,
- span: Span,
- ) -> Vec<ImpliedBound<'tcx>> {
- let tcx = infcx.tcx;
-
- // Sometimes when we ask what it takes for T: WF, we get back that
- // U: WF is required; in that case, we push U onto this stack and
- // process it next. Currently (at least) these resulting
- // predicates are always guaranteed to be a subset of the original
- // type, so we need not fear non-termination.
- let mut wf_types = vec![ty];
-
- let mut implied_bounds = vec![];
-
- let mut fulfill_cx = FulfillmentContext::new();
-
- while let Some(ty) = wf_types.pop() {
- // Compute the obligations for `ty` to be well-formed. If `ty` is
- // an unresolved inference variable, just substituted an empty set
- // -- because the return type here is going to be things we *add*
- // to the environment, it's always ok for this set to be smaller
- // than the ultimate set. (Note: normally there won't be
- // unresolved inference variables here anyway, but there might be
- // during typeck under some circumstances.)
- let obligations =
- wf::obligations(infcx, self.param_env, body_id, ty, span).unwrap_or(vec![]);
-
- // NB: All of these predicates *ought* to be easily proven
- // true. In fact, their correctness is (mostly) implied by
- // other parts of the program. However, in #42552, we had
- // an annoying scenario where:
- //
- // - Some `T::Foo` gets normalized, resulting in a
- // variable `_1` and a `T: Trait<Foo=_1>` constraint
- // (not sure why it couldn't immediately get
- // solved). This result of `_1` got cached.
- // - These obligations were dropped on the floor here,
- // rather than being registered.
- // - Then later we would get a request to normalize
- // `T::Foo` which would result in `_1` being used from
- // the cache, but hence without the `T: Trait<Foo=_1>`
- // constraint. As a result, `_1` never gets resolved,
- // and we get an ICE (in dropck).
- //
- // Therefore, we register any predicates involving
- // inference variables. We restrict ourselves to those
- // involving inference variables both for efficiency and
- // to avoids duplicate errors that otherwise show up.
- fulfill_cx.register_predicate_obligations(
- infcx,
- obligations
- .iter()
- .filter(|o| o.predicate.has_infer_types())
- .cloned());
-
- // From the full set of obligations, just filter down to the
- // region relationships.
- implied_bounds.extend(obligations.into_iter().flat_map(|obligation| {
- assert!(!obligation.has_escaping_regions());
- match obligation.predicate {
- ty::Predicate::Trait(..) |
- ty::Predicate::Equate(..) |
- ty::Predicate::Subtype(..) |
- ty::Predicate::Projection(..) |
- ty::Predicate::ClosureKind(..) |
- ty::Predicate::ObjectSafe(..) |
- ty::Predicate::ConstEvaluatable(..) => vec![],
-
- ty::Predicate::WellFormed(subty) => {
- wf_types.push(subty);
- vec![]
- }
-
- ty::Predicate::RegionOutlives(ref data) => {
- match tcx.no_late_bound_regions(data) {
- None => vec![],
- Some(ty::OutlivesPredicate(r_a, r_b)) => {
- vec![ImpliedBound::RegionSubRegion(r_b, r_a)]
- }
- }
- }
-
- ty::Predicate::TypeOutlives(ref data) => {
- match tcx.no_late_bound_regions(data) {
- None => vec![],
- Some(ty::OutlivesPredicate(ty_a, r_b)) => {
- let ty_a = infcx.resolve_type_vars_if_possible(&ty_a);
- let components = tcx.outlives_components(ty_a);
- self.implied_bounds_from_components(r_b, components)
- }
- }
- }
- }
- }));
- }
-
- // Ensure that those obligations that we had to solve
- // get solved *here*.
- match fulfill_cx.select_all_or_error(infcx) {
- Ok(()) => (),
- Err(errors) => infcx.report_fulfillment_errors(&errors, None),
- }
-
- implied_bounds
- }
-
- /// When we have an implied bound that `T: 'a`, we can further break
- /// this down to determine what relationships would have to hold for
- /// `T: 'a` to hold. We get to assume that the caller has validated
- /// those relationships.
- fn implied_bounds_from_components(
- &self,
- sub_region: ty::Region<'tcx>,
- sup_components: Vec<Component<'tcx>>,
- ) -> Vec<ImpliedBound<'tcx>> {
- sup_components
- .into_iter()
- .flat_map(|component| {
- match component {
- Component::Region(r) =>
- vec![ImpliedBound::RegionSubRegion(sub_region, r)],
- Component::Param(p) =>
- vec![ImpliedBound::RegionSubParam(sub_region, p)],
- Component::Projection(p) =>
- vec![ImpliedBound::RegionSubProjection(sub_region, p)],
- Component::EscapingProjection(_) =>
- // If the projection has escaping regions, don't
- // try to infer any implied bounds even for its
- // free components. This is conservative, because
- // the caller will still have to prove that those
- // free components outlive `sub_region`. But the
- // idea is that the WAY that the caller proves
- // that may change in the future and we want to
- // give ourselves room to get smarter here.
- vec![],
- Component::UnresolvedInferenceVariable(..) =>
- vec![],
- }
- })
- .collect()
- }
}
--- /dev/null
+// Copyright 2012-2014 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.
+
+use infer::InferCtxt;
+use syntax::ast;
+use syntax::codemap::Span;
+use traits::FulfillmentContext;
+use ty::{self, Ty, TypeFoldable};
+use ty::outlives::Component;
+use ty::wf;
+
+/// Implied bounds are region relationships that we deduce
+/// automatically. The idea is that (e.g.) a caller must check that a
+/// function's argument types are well-formed immediately before
+/// calling that fn, and hence the *callee* can assume that its
+/// argument types are well-formed. This may imply certain relationships
+/// between generic parameters. For example:
+///
+/// fn foo<'a,T>(x: &'a T)
+///
+/// can only be called with a `'a` and `T` such that `&'a T` is WF.
+/// For `&'a T` to be WF, `T: 'a` must hold. So we can assume `T: 'a`.
+#[derive(Debug)]
+pub enum ImpliedBound<'tcx> {
+ RegionSubRegion(ty::Region<'tcx>, ty::Region<'tcx>),
+ RegionSubParam(ty::Region<'tcx>, ty::ParamTy),
+ RegionSubProjection(ty::Region<'tcx>, ty::ProjectionTy<'tcx>),
+}
+
+impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
+ /// Compute the implied bounds that a callee/impl can assume based on
+ /// the fact that caller/projector has ensured that `ty` is WF. See
+ /// the `ImpliedBound` type for more details.
+ ///
+ /// # Parameters
+ ///
+ /// - `param_env`, the where-clauses in scope
+ /// - `body_id`, the body-id to use when normalizing assoc types.
+ /// Note that this may cause outlives obligations to be injected
+ /// into the inference context with this body-id.
+ /// - `ty`, the type that we are supposed to assume is WF.
+ /// - `span`, a span to use when normalizing, hopefully not important,
+ /// might be useful if a `bug!` occurs.
+ pub fn implied_bounds(
+ &self,
+ param_env: ty::ParamEnv<'tcx>,
+ body_id: ast::NodeId,
+ ty: Ty<'tcx>,
+ span: Span,
+ ) -> Vec<ImpliedBound<'tcx>> {
+ let tcx = self.tcx;
+
+ // Sometimes when we ask what it takes for T: WF, we get back that
+ // U: WF is required; in that case, we push U onto this stack and
+ // process it next. Currently (at least) these resulting
+ // predicates are always guaranteed to be a subset of the original
+ // type, so we need not fear non-termination.
+ let mut wf_types = vec![ty];
+
+ let mut implied_bounds = vec![];
+
+ let mut fulfill_cx = FulfillmentContext::new();
+
+ while let Some(ty) = wf_types.pop() {
+ // Compute the obligations for `ty` to be well-formed. If `ty` is
+ // an unresolved inference variable, just substituted an empty set
+ // -- because the return type here is going to be things we *add*
+ // to the environment, it's always ok for this set to be smaller
+ // than the ultimate set. (Note: normally there won't be
+ // unresolved inference variables here anyway, but there might be
+ // during typeck under some circumstances.)
+ let obligations =
+ wf::obligations(self, param_env, body_id, ty, span).unwrap_or(vec![]);
+
+ // NB: All of these predicates *ought* to be easily proven
+ // true. In fact, their correctness is (mostly) implied by
+ // other parts of the program. However, in #42552, we had
+ // an annoying scenario where:
+ //
+ // - Some `T::Foo` gets normalized, resulting in a
+ // variable `_1` and a `T: Trait<Foo=_1>` constraint
+ // (not sure why it couldn't immediately get
+ // solved). This result of `_1` got cached.
+ // - These obligations were dropped on the floor here,
+ // rather than being registered.
+ // - Then later we would get a request to normalize
+ // `T::Foo` which would result in `_1` being used from
+ // the cache, but hence without the `T: Trait<Foo=_1>`
+ // constraint. As a result, `_1` never gets resolved,
+ // and we get an ICE (in dropck).
+ //
+ // Therefore, we register any predicates involving
+ // inference variables. We restrict ourselves to those
+ // involving inference variables both for efficiency and
+ // to avoids duplicate errors that otherwise show up.
+ fulfill_cx.register_predicate_obligations(
+ self,
+ obligations
+ .iter()
+ .filter(|o| o.predicate.has_infer_types())
+ .cloned());
+
+ // From the full set of obligations, just filter down to the
+ // region relationships.
+ implied_bounds.extend(obligations.into_iter().flat_map(|obligation| {
+ assert!(!obligation.has_escaping_regions());
+ match obligation.predicate {
+ ty::Predicate::Trait(..) |
+ ty::Predicate::Equate(..) |
+ ty::Predicate::Subtype(..) |
+ ty::Predicate::Projection(..) |
+ ty::Predicate::ClosureKind(..) |
+ ty::Predicate::ObjectSafe(..) |
+ ty::Predicate::ConstEvaluatable(..) => vec![],
+
+ ty::Predicate::WellFormed(subty) => {
+ wf_types.push(subty);
+ vec![]
+ }
+
+ ty::Predicate::RegionOutlives(ref data) => {
+ match tcx.no_late_bound_regions(data) {
+ None => vec![],
+ Some(ty::OutlivesPredicate(r_a, r_b)) => {
+ vec![ImpliedBound::RegionSubRegion(r_b, r_a)]
+ }
+ }
+ }
+
+ ty::Predicate::TypeOutlives(ref data) => {
+ match tcx.no_late_bound_regions(data) {
+ None => vec![],
+ Some(ty::OutlivesPredicate(ty_a, r_b)) => {
+ let ty_a = self.resolve_type_vars_if_possible(&ty_a);
+ let components = tcx.outlives_components(ty_a);
+ Self::implied_bounds_from_components(r_b, components)
+ }
+ }
+ }
+ }
+ }));
+ }
+
+ // Ensure that those obligations that we had to solve
+ // get solved *here*.
+ match fulfill_cx.select_all_or_error(self) {
+ Ok(()) => (),
+ Err(errors) => self.report_fulfillment_errors(&errors, None),
+ }
+
+ implied_bounds
+ }
+
+ /// When we have an implied bound that `T: 'a`, we can further break
+ /// this down to determine what relationships would have to hold for
+ /// `T: 'a` to hold. We get to assume that the caller has validated
+ /// those relationships.
+ fn implied_bounds_from_components(
+ sub_region: ty::Region<'tcx>,
+ sup_components: Vec<Component<'tcx>>,
+ ) -> Vec<ImpliedBound<'tcx>> {
+ sup_components
+ .into_iter()
+ .flat_map(|component| {
+ match component {
+ Component::Region(r) =>
+ vec![ImpliedBound::RegionSubRegion(sub_region, r)],
+ Component::Param(p) =>
+ vec![ImpliedBound::RegionSubParam(sub_region, p)],
+ Component::Projection(p) =>
+ vec![ImpliedBound::RegionSubProjection(sub_region, p)],
+ Component::EscapingProjection(_) =>
+ // If the projection has escaping regions, don't
+ // try to infer any implied bounds even for its
+ // free components. This is conservative, because
+ // the caller will still have to prove that those
+ // free components outlive `sub_region`. But the
+ // idea is that the WAY that the caller proves
+ // that may change in the future and we want to
+ // give ourselves room to get smarter here.
+ vec![],
+ Component::UnresolvedInferenceVariable(..) =>
+ vec![],
+ }
+ })
+ .collect()
+ }
+}
projects / rust.git / commitdiff