diff options
Diffstat (limited to '')
| -rw-r--r-- | compiler/rustc_traits/src/dropck_outlives.rs | 220 |
1 files changed, 106 insertions, 114 deletions
diff --git a/compiler/rustc_traits/src/dropck_outlives.rs b/compiler/rustc_traits/src/dropck_outlives.rs index a20de08b4..d5a8ca5ea 100644 --- a/compiler/rustc_traits/src/dropck_outlives.rs +++ b/compiler/rustc_traits/src/dropck_outlives.rs @@ -4,7 +4,7 @@ use rustc_infer::infer::canonical::{Canonical, QueryResponse}; use rustc_infer::infer::TyCtxtInferExt; use rustc_infer::traits::TraitEngineExt as _; use rustc_middle::ty::query::Providers; -use rustc_middle::ty::subst::{InternalSubsts, Subst}; +use rustc_middle::ty::InternalSubsts; use rustc_middle::ty::{self, EarlyBinder, ParamEnvAnd, Ty, TyCtxt}; use rustc_span::source_map::{Span, DUMMY_SP}; use rustc_trait_selection::traits::query::dropck_outlives::trivial_dropck_outlives; @@ -27,128 +27,120 @@ fn dropck_outlives<'tcx>( ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, DropckOutlivesResult<'tcx>>>, NoSolution> { debug!("dropck_outlives(goal={:#?})", canonical_goal); - tcx.infer_ctxt().enter_with_canonical( - DUMMY_SP, - &canonical_goal, - |ref infcx, goal, canonical_inference_vars| { - let tcx = infcx.tcx; - let ParamEnvAnd { param_env, value: for_ty } = goal; - - let mut result = DropckOutlivesResult { kinds: vec![], overflows: vec![] }; - - // A stack of types left to process. Each round, we pop - // something from the stack and invoke - // `dtorck_constraint_for_ty`. This may produce new types that - // have to be pushed on the stack. This continues until we have explored - // all the reachable types from the type `for_ty`. - // - // Example: Imagine that we have the following code: - // - // ```rust - // struct A { - // value: B, - // children: Vec<A>, - // } - // - // struct B { - // value: u32 - // } - // - // fn f() { - // let a: A = ...; - // .. - // } // here, `a` is dropped - // ``` - // - // at the point where `a` is dropped, we need to figure out - // which types inside of `a` contain region data that may be - // accessed by any destructors in `a`. We begin by pushing `A` - // onto the stack, as that is the type of `a`. We will then - // invoke `dtorck_constraint_for_ty` which will expand `A` - // into the types of its fields `(B, Vec<A>)`. These will get - // pushed onto the stack. Eventually, expanding `Vec<A>` will - // lead to us trying to push `A` a second time -- to prevent - // infinite recursion, we notice that `A` was already pushed - // once and stop. - let mut ty_stack = vec![(for_ty, 0)]; - - // Set used to detect infinite recursion. - let mut ty_set = FxHashSet::default(); - - let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx); - - let cause = ObligationCause::dummy(); - let mut constraints = DropckConstraint::empty(); - while let Some((ty, depth)) = ty_stack.pop() { - debug!( - "{} kinds, {} overflows, {} ty_stack", - result.kinds.len(), - result.overflows.len(), - ty_stack.len() - ); - dtorck_constraint_for_ty(tcx, DUMMY_SP, for_ty, depth, ty, &mut constraints)?; - - // "outlives" represent types/regions that may be touched - // by a destructor. - result.kinds.append(&mut constraints.outlives); - result.overflows.append(&mut constraints.overflows); - - // If we have even one overflow, we should stop trying to evaluate further -- - // chances are, the subsequent overflows for this evaluation won't provide useful - // information and will just decrease the speed at which we can emit these errors - // (since we'll be printing for just that much longer for the often enormous types - // that result here). - if !result.overflows.is_empty() { - break; - } + let (ref infcx, goal, canonical_inference_vars) = + tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal); + let tcx = infcx.tcx; + let ParamEnvAnd { param_env, value: for_ty } = goal; + + let mut result = DropckOutlivesResult { kinds: vec![], overflows: vec![] }; + + // A stack of types left to process. Each round, we pop + // something from the stack and invoke + // `dtorck_constraint_for_ty`. This may produce new types that + // have to be pushed on the stack. This continues until we have explored + // all the reachable types from the type `for_ty`. + // + // Example: Imagine that we have the following code: + // + // ```rust + // struct A { + // value: B, + // children: Vec<A>, + // } + // + // struct B { + // value: u32 + // } + // + // fn f() { + // let a: A = ...; + // .. + // } // here, `a` is dropped + // ``` + // + // at the point where `a` is dropped, we need to figure out + // which types inside of `a` contain region data that may be + // accessed by any destructors in `a`. We begin by pushing `A` + // onto the stack, as that is the type of `a`. We will then + // invoke `dtorck_constraint_for_ty` which will expand `A` + // into the types of its fields `(B, Vec<A>)`. These will get + // pushed onto the stack. Eventually, expanding `Vec<A>` will + // lead to us trying to push `A` a second time -- to prevent + // infinite recursion, we notice that `A` was already pushed + // once and stop. + let mut ty_stack = vec![(for_ty, 0)]; + + // Set used to detect infinite recursion. + let mut ty_set = FxHashSet::default(); + + let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx); + + let cause = ObligationCause::dummy(); + let mut constraints = DropckConstraint::empty(); + while let Some((ty, depth)) = ty_stack.pop() { + debug!( + "{} kinds, {} overflows, {} ty_stack", + result.kinds.len(), + result.overflows.len(), + ty_stack.len() + ); + dtorck_constraint_for_ty(tcx, DUMMY_SP, for_ty, depth, ty, &mut constraints)?; + + // "outlives" represent types/regions that may be touched + // by a destructor. + result.kinds.append(&mut constraints.outlives); + result.overflows.append(&mut constraints.overflows); + + // If we have even one overflow, we should stop trying to evaluate further -- + // chances are, the subsequent overflows for this evaluation won't provide useful + // information and will just decrease the speed at which we can emit these errors + // (since we'll be printing for just that much longer for the often enormous types + // that result here). + if !result.overflows.is_empty() { + break; + } - // dtorck types are "types that will get dropped but which - // do not themselves define a destructor", more or less. We have - // to push them onto the stack to be expanded. - for ty in constraints.dtorck_types.drain(..) { - match infcx.at(&cause, param_env).normalize(ty) { - Ok(Normalized { value: ty, obligations }) => { - fulfill_cx.register_predicate_obligations(infcx, obligations); - - debug!("dropck_outlives: ty from dtorck_types = {:?}", ty); - - match ty.kind() { - // All parameters live for the duration of the - // function. - ty::Param(..) => {} - - // A projection that we couldn't resolve - it - // might have a destructor. - ty::Projection(..) | ty::Opaque(..) => { - result.kinds.push(ty.into()); - } - - _ => { - if ty_set.insert(ty) { - ty_stack.push((ty, depth + 1)); - } - } - } + // dtorck types are "types that will get dropped but which + // do not themselves define a destructor", more or less. We have + // to push them onto the stack to be expanded. + for ty in constraints.dtorck_types.drain(..) { + match infcx.at(&cause, param_env).normalize(ty) { + Ok(Normalized { value: ty, obligations }) => { + fulfill_cx.register_predicate_obligations(infcx, obligations); + + debug!("dropck_outlives: ty from dtorck_types = {:?}", ty); + + match ty.kind() { + // All parameters live for the duration of the + // function. + ty::Param(..) => {} + + // A projection that we couldn't resolve - it + // might have a destructor. + ty::Projection(..) | ty::Opaque(..) => { + result.kinds.push(ty.into()); } - // We don't actually expect to fail to normalize. - // That implies a WF error somewhere else. - Err(NoSolution) => { - return Err(NoSolution); + _ => { + if ty_set.insert(ty) { + ty_stack.push((ty, depth + 1)); + } } } } + + // We don't actually expect to fail to normalize. + // That implies a WF error somewhere else. + Err(NoSolution) => { + return Err(NoSolution); + } } + } + } - debug!("dropck_outlives: result = {:#?}", result); + debug!("dropck_outlives: result = {:#?}", result); - infcx.make_canonicalized_query_response( - canonical_inference_vars, - result, - &mut *fulfill_cx, - ) - }, - ) + infcx.make_canonicalized_query_response(canonical_inference_vars, result, &mut *fulfill_cx) } /// Returns a set of constraints that needs to be satisfied in |