diff --git a/src/librustc/traits/fulfill.rs b/src/librustc/traits/fulfill.rs index f47c336656b..826d4a28158 100644 --- a/src/librustc/traits/fulfill.rs +++ b/src/librustc/traits/fulfill.rs @@ -8,15 +8,14 @@ // option. This file may not be copied, modified, or distributed // except according to those terms. -use dep_graph::DepGraph; use infer::{InferCtxt, InferOk}; -use ty::{self, Ty, TypeFoldable, ToPolyTraitRef, TyCtxt, ToPredicate}; +use ty::{self, Ty, TypeFoldable, ToPolyTraitRef, ToPredicate}; use ty::error::ExpectedFound; use rustc_data_structures::obligation_forest::{ObligationForest, Error}; use rustc_data_structures::obligation_forest::{ForestObligation, ObligationProcessor}; use std::marker::PhantomData; use syntax::ast; -use util::nodemap::{FxHashSet, NodeMap}; +use util::nodemap::NodeMap; use hir::def_id::DefId; use super::CodeAmbiguity; @@ -34,11 +33,6 @@ impl<'tcx> ForestObligation for PendingPredicateObligation<'tcx> { fn as_predicate(&self) -> &Self::Predicate { &self.obligation.predicate } } -pub struct GlobalFulfilledPredicates<'tcx> { - set: FxHashSet>, - dep_graph: DepGraph, -} - /// The fulfillment context is used to drive trait resolution. It /// consists of a list of obligations that must be (eventually) /// satisfied. The job is to track which are satisfied, which yielded @@ -183,13 +177,6 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> { assert!(!infcx.is_in_snapshot()); - let tcx = infcx.tcx; - - if tcx.fulfilled_predicates.borrow().check_duplicate(tcx, &obligation.predicate) { - debug!("register_predicate_obligation: duplicate"); - return - } - self.predicates.register_obligation(PendingPredicateObligation { obligation, stalled_on: vec![] @@ -264,13 +251,6 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> { }); debug!("select: outcome={:?}", outcome); - // these are obligations that were proven to be true. - for pending_obligation in outcome.completed { - let predicate = &pending_obligation.obligation.predicate; - selcx.tcx().fulfilled_predicates.borrow_mut() - .add_if_global(selcx.tcx(), predicate); - } - errors.extend( outcome.errors.into_iter() .map(|e| to_fulfillment_error(e))); @@ -375,21 +355,31 @@ fn process_predicate<'a, 'gcx, 'tcx>( match obligation.predicate { ty::Predicate::Trait(ref data) => { - let tcx = selcx.tcx(); - if tcx.fulfilled_predicates.borrow().check_duplicate_trait(tcx, data) { - return Ok(Some(vec![])); + let trait_obligation = obligation.with(data.clone()); + + if data.is_global() { + // no type variables present, can use evaluation for better caching. + // FIXME: consider caching errors too. + if + // make defaulted unit go through the slow path for better warnings, + // please remove this when the warnings are removed. + !trait_obligation.predicate.skip_binder().self_ty().is_defaulted_unit() && + selcx.evaluate_obligation_conservatively(&obligation) { + debug!("selecting trait `{:?}` at depth {} evaluated to holds", + data, obligation.recursion_depth); + return Ok(Some(vec![])) + } } - let trait_obligation = obligation.with(data.clone()); match selcx.select(&trait_obligation) { Ok(Some(vtable)) => { debug!("selecting trait `{:?}` at depth {} yielded Ok(Some)", - data, obligation.recursion_depth); + data, obligation.recursion_depth); Ok(Some(vtable.nested_obligations())) } Ok(None) => { debug!("selecting trait `{:?}` at depth {} yielded Ok(None)", - data, obligation.recursion_depth); + data, obligation.recursion_depth); // This is a bit subtle: for the most part, the // only reason we can fail to make progress on @@ -568,55 +558,6 @@ fn register_region_obligation<'tcx>(t_a: Ty<'tcx>, } -impl<'a, 'gcx, 'tcx> GlobalFulfilledPredicates<'gcx> { - pub fn new(dep_graph: DepGraph) -> GlobalFulfilledPredicates<'gcx> { - GlobalFulfilledPredicates { - set: FxHashSet(), - dep_graph, - } - } - - pub fn check_duplicate(&self, tcx: TyCtxt, key: &ty::Predicate<'tcx>) -> bool { - if let ty::Predicate::Trait(ref data) = *key { - self.check_duplicate_trait(tcx, data) - } else { - false - } - } - - pub fn check_duplicate_trait(&self, tcx: TyCtxt, data: &ty::PolyTraitPredicate<'tcx>) -> bool { - // For the global predicate registry, when we find a match, it - // may have been computed by some other task, so we want to - // add a read from the node corresponding to the predicate - // processing to make sure we get the transitive dependencies. - if self.set.contains(data) { - debug_assert!(data.is_global()); - self.dep_graph.read(data.dep_node(tcx)); - debug!("check_duplicate: global predicate `{:?}` already proved elsewhere", data); - - true - } else { - false - } - } - - fn add_if_global(&mut self, tcx: TyCtxt<'a, 'gcx, 'tcx>, key: &ty::Predicate<'tcx>) { - if let ty::Predicate::Trait(ref data) = *key { - // We only add things to the global predicate registry - // after the current task has proved them, and hence - // already has the required read edges, so we don't need - // to add any more edges here. - if data.is_global() { - if let Some(data) = tcx.lift_to_global(data) { - if self.set.insert(data.clone()) { - debug!("add_if_global: global predicate `{:?}` added", data); - } - } - } - } - } -} - fn to_fulfillment_error<'tcx>( error: Error, FulfillmentErrorCode<'tcx>>) -> FulfillmentError<'tcx> diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs index 6b243ffa5fe..e14203b34a1 100644 --- a/src/librustc/traits/mod.rs +++ b/src/librustc/traits/mod.rs @@ -31,7 +31,7 @@ use syntax_pos::{Span, DUMMY_SP}; pub use self::coherence::orphan_check; pub use self::coherence::overlapping_impls; pub use self::coherence::OrphanCheckErr; -pub use self::fulfill::{FulfillmentContext, GlobalFulfilledPredicates, RegionObligation}; +pub use self::fulfill::{FulfillmentContext, RegionObligation}; pub use self::project::MismatchedProjectionTypes; pub use self::project::{normalize, normalize_projection_type, Normalized}; pub use self::project::{ProjectionCache, ProjectionCacheSnapshot, Reveal}; diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs index e9a89b1bc37..bb46e8a8af1 100644 --- a/src/librustc/traits/select.rs +++ b/src/librustc/traits/select.rs @@ -514,21 +514,11 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> { debug!("evaluate_predicate_recursively({:?})", obligation); - let tcx = self.tcx(); - - // Check the cache from the tcx of predicates that we know - // have been proven elsewhere. This cache only contains - // predicates that are global in scope and hence unaffected by - // the current environment. - if tcx.fulfilled_predicates.borrow().check_duplicate(tcx, &obligation.predicate) { - return EvaluatedToOk; - } - match obligation.predicate { ty::Predicate::Trait(ref t) => { assert!(!t.has_escaping_regions()); let obligation = obligation.with(t.clone()); - self.evaluate_obligation_recursively(previous_stack, &obligation) + self.evaluate_trait_predicate_recursively(previous_stack, obligation) } ty::Predicate::Equate(ref p) => { @@ -613,15 +603,23 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> { } } - fn evaluate_obligation_recursively<'o>(&mut self, - previous_stack: TraitObligationStackList<'o, 'tcx>, - obligation: &TraitObligation<'tcx>) - -> EvaluationResult + fn evaluate_trait_predicate_recursively<'o>(&mut self, + previous_stack: TraitObligationStackList<'o, 'tcx>, + mut obligation: TraitObligation<'tcx>) + -> EvaluationResult { - debug!("evaluate_obligation_recursively({:?})", + debug!("evaluate_trait_predicate_recursively({:?})", obligation); - let stack = self.push_stack(previous_stack, obligation); + if !self.intercrate && obligation.is_global() { + // If a param env is consistent, global obligations do not depend on its particular + // value in order to work, so we can clear out the param env and get better + // caching. (If the current param env is inconsistent, we don't care what happens). + debug!("evaluate_trait_predicate_recursively({:?}) - in global", obligation); + obligation.param_env = ty::ParamEnv::empty(obligation.param_env.reveal); + } + + let stack = self.push_stack(previous_stack, &obligation); let fresh_trait_ref = stack.fresh_trait_ref; if let Some(result) = self.check_evaluation_cache(obligation.param_env, fresh_trait_ref) { debug!("CACHE HIT: EVAL({:?})={:?}", @@ -676,8 +674,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> { } if unbound_input_types && stack.iter().skip(1).any( - |prev| self.match_fresh_trait_refs(&stack.fresh_trait_ref, - &prev.fresh_trait_ref)) + |prev| stack.obligation.param_env == prev.obligation.param_env && + self.match_fresh_trait_refs(&stack.fresh_trait_ref, + &prev.fresh_trait_ref)) { debug!("evaluate_stack({:?}) --> unbound argument, recursive --> giving up", stack.fresh_trait_ref); @@ -706,7 +705,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> { if let Some(rec_index) = stack.iter() .skip(1) // skip top-most frame - .position(|prev| stack.fresh_trait_ref == prev.fresh_trait_ref) + .position(|prev| stack.obligation.param_env == prev.obligation.param_env && + stack.fresh_trait_ref == prev.fresh_trait_ref) { debug!("evaluate_stack({:?}) --> recursive", stack.fresh_trait_ref); diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs index 316f871a7a4..1f20993f96c 100644 --- a/src/librustc/ty/context.rs +++ b/src/librustc/ty/context.rs @@ -507,12 +507,6 @@ pub struct GlobalCtxt<'tcx> { /// Merge this with `selection_cache`? pub evaluation_cache: traits::EvaluationCache<'tcx>, - /// A set of predicates that have been fulfilled *somewhere*. - /// This is used to avoid duplicate work. Predicates are only - /// added to this set when they mention only "global" names - /// (i.e., no type or lifetime parameters). - pub fulfilled_predicates: RefCell>, - /// Maps Expr NodeId's to `true` iff `&expr` can have 'static lifetime. pub rvalue_promotable_to_static: RefCell>, @@ -686,7 +680,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> { let interners = CtxtInterners::new(arena); let common_types = CommonTypes::new(&interners); let dep_graph = hir.dep_graph.clone(); - let fulfilled_predicates = traits::GlobalFulfilledPredicates::new(dep_graph.clone()); let max_cnum = s.cstore.crates().iter().map(|c| c.as_usize()).max().unwrap_or(0); let mut providers = IndexVec::from_elem_n(extern_providers, max_cnum + 1); providers[LOCAL_CRATE] = local_providers; @@ -735,7 +728,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> { named_region_map, trait_map: resolutions.trait_map, export_map: resolutions.export_map, - fulfilled_predicates: RefCell::new(fulfilled_predicates), hir, def_path_hash_to_def_id, maps: maps::Maps::new(providers), diff --git a/src/test/compile-fail/issue-39970.rs b/src/test/compile-fail/issue-39970.rs new file mode 100644 index 00000000000..65ea1baa4a1 --- /dev/null +++ b/src/test/compile-fail/issue-39970.rs @@ -0,0 +1,31 @@ +// Copyright 2017 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +trait Array<'a> { + type Element: 'a; +} + +trait Visit { + fn visit() {} +} + +impl<'a> Array<'a> for () { + type Element = &'a (); +} + +impl Visit for () where + //(): for<'a> Array<'a, Element=&'a ()>, // No ICE + (): for<'a> Array<'a, Element=()>, // ICE +{} + +fn main() { + <() as Visit>::visit(); + //~^ ERROR type mismatch resolving `for<'a> <() as Array<'a>>::Element == ()` +} diff --git a/src/test/compile-fail/issue-42796.rs b/src/test/compile-fail/issue-42796.rs new file mode 100644 index 00000000000..10622eccbdc --- /dev/null +++ b/src/test/compile-fail/issue-42796.rs @@ -0,0 +1,29 @@ +// Copyright 2017 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +pub trait Mirror { + type Image; +} + +impl Mirror for T { + type Image = T; +} + +pub fn poison(victim: String) where >::Image: Copy { + loop { drop(victim); } //~ ERROR use of moved value +} + +fn main() { + let s = "Hello!".to_owned(); + let mut s_copy = s; + s_copy.push_str("World!"); + "0wned!".to_owned(); + println!("{}", s); //~ ERROR use of moved value +}