| //! The `Visitor` responsible for actually checking a `mir::Body` for invalid operations. |
| |
| use rustc_errors::{Applicability, Diagnostic, ErrorReported}; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::{self as hir, HirId, LangItem}; |
| use rustc_index::bit_set::BitSet; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_infer::traits::{ImplSource, Obligation, ObligationCause}; |
| use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor}; |
| use rustc_middle::mir::*; |
| use rustc_middle::ty::cast::CastTy; |
| use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts}; |
| use rustc_middle::ty::{self, adjustment::PointerCast, Instance, InstanceDef, Ty, TyCtxt}; |
| use rustc_middle::ty::{Binder, TraitPredicate, TraitRef}; |
| use rustc_span::{sym, Span, Symbol}; |
| use rustc_trait_selection::traits::error_reporting::InferCtxtExt; |
| use rustc_trait_selection::traits::{self, SelectionContext, TraitEngine}; |
| |
| use std::mem; |
| use std::ops::Deref; |
| |
| use super::ops::{self, NonConstOp, Status}; |
| use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop}; |
| use super::resolver::FlowSensitiveAnalysis; |
| use super::{is_lang_panic_fn, ConstCx, Qualif}; |
| use crate::const_eval::is_unstable_const_fn; |
| use crate::dataflow::impls::MaybeMutBorrowedLocals; |
| use crate::dataflow::{self, Analysis}; |
| |
| // We are using `MaybeMutBorrowedLocals` as a proxy for whether an item may have been mutated |
| // through a pointer prior to the given point. This is okay even though `MaybeMutBorrowedLocals` |
| // kills locals upon `StorageDead` because a local will never be used after a `StorageDead`. |
| type IndirectlyMutableResults<'mir, 'tcx> = |
| dataflow::ResultsCursor<'mir, 'tcx, MaybeMutBorrowedLocals<'mir, 'tcx>>; |
| |
| type QualifResults<'mir, 'tcx, Q> = |
| dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'mir, 'mir, 'tcx, Q>>; |
| |
| #[derive(Default)] |
| pub struct Qualifs<'mir, 'tcx> { |
| has_mut_interior: Option<QualifResults<'mir, 'tcx, HasMutInterior>>, |
| needs_drop: Option<QualifResults<'mir, 'tcx, NeedsDrop>>, |
| indirectly_mutable: Option<IndirectlyMutableResults<'mir, 'tcx>>, |
| } |
| |
| impl Qualifs<'mir, 'tcx> { |
| pub fn indirectly_mutable( |
| &mut self, |
| ccx: &'mir ConstCx<'mir, 'tcx>, |
| local: Local, |
| location: Location, |
| ) -> bool { |
| let indirectly_mutable = self.indirectly_mutable.get_or_insert_with(|| { |
| let ConstCx { tcx, body, param_env, .. } = *ccx; |
| |
| // We can use `unsound_ignore_borrow_on_drop` here because custom drop impls are not |
| // allowed in a const. |
| // |
| // FIXME(ecstaticmorse): Someday we want to allow custom drop impls. How do we do this |
| // without breaking stable code? |
| MaybeMutBorrowedLocals::mut_borrows_only(tcx, &body, param_env) |
| .unsound_ignore_borrow_on_drop() |
| .into_engine(tcx, &body) |
| .pass_name("const_qualification") |
| .iterate_to_fixpoint() |
| .into_results_cursor(&body) |
| }); |
| |
| indirectly_mutable.seek_before_primary_effect(location); |
| indirectly_mutable.get().contains(local) |
| } |
| |
| /// Returns `true` if `local` is `NeedsDrop` at the given `Location`. |
| /// |
| /// Only updates the cursor if absolutely necessary |
| pub fn needs_drop( |
| &mut self, |
| ccx: &'mir ConstCx<'mir, 'tcx>, |
| local: Local, |
| location: Location, |
| ) -> bool { |
| let ty = ccx.body.local_decls[local].ty; |
| if !NeedsDrop::in_any_value_of_ty(ccx, ty) { |
| return false; |
| } |
| |
| let needs_drop = self.needs_drop.get_or_insert_with(|| { |
| let ConstCx { tcx, body, .. } = *ccx; |
| |
| FlowSensitiveAnalysis::new(NeedsDrop, ccx) |
| .into_engine(tcx, &body) |
| .iterate_to_fixpoint() |
| .into_results_cursor(&body) |
| }); |
| |
| needs_drop.seek_before_primary_effect(location); |
| needs_drop.get().contains(local) || self.indirectly_mutable(ccx, local, location) |
| } |
| |
| /// Returns `true` if `local` is `HasMutInterior` at the given `Location`. |
| /// |
| /// Only updates the cursor if absolutely necessary. |
| pub fn has_mut_interior( |
| &mut self, |
| ccx: &'mir ConstCx<'mir, 'tcx>, |
| local: Local, |
| location: Location, |
| ) -> bool { |
| let ty = ccx.body.local_decls[local].ty; |
| if !HasMutInterior::in_any_value_of_ty(ccx, ty) { |
| return false; |
| } |
| |
| let has_mut_interior = self.has_mut_interior.get_or_insert_with(|| { |
| let ConstCx { tcx, body, .. } = *ccx; |
| |
| FlowSensitiveAnalysis::new(HasMutInterior, ccx) |
| .into_engine(tcx, &body) |
| .iterate_to_fixpoint() |
| .into_results_cursor(&body) |
| }); |
| |
| has_mut_interior.seek_before_primary_effect(location); |
| has_mut_interior.get().contains(local) || self.indirectly_mutable(ccx, local, location) |
| } |
| |
| fn in_return_place( |
| &mut self, |
| ccx: &'mir ConstCx<'mir, 'tcx>, |
| error_occured: Option<ErrorReported>, |
| ) -> ConstQualifs { |
| // Find the `Return` terminator if one exists. |
| // |
| // If no `Return` terminator exists, this MIR is divergent. Just return the conservative |
| // qualifs for the return type. |
| let return_block = ccx |
| .body |
| .basic_blocks() |
| .iter_enumerated() |
| .find(|(_, block)| match block.terminator().kind { |
| TerminatorKind::Return => true, |
| _ => false, |
| }) |
| .map(|(bb, _)| bb); |
| |
| let return_block = match return_block { |
| None => return qualifs::in_any_value_of_ty(ccx, ccx.body.return_ty(), error_occured), |
| Some(bb) => bb, |
| }; |
| |
| let return_loc = ccx.body.terminator_loc(return_block); |
| |
| let custom_eq = match ccx.const_kind() { |
| // We don't care whether a `const fn` returns a value that is not structurally |
| // matchable. Functions calls are opaque and always use type-based qualification, so |
| // this value should never be used. |
| hir::ConstContext::ConstFn => true, |
| |
| // If we know that all values of the return type are structurally matchable, there's no |
| // need to run dataflow. |
| _ if !CustomEq::in_any_value_of_ty(ccx, ccx.body.return_ty()) => false, |
| |
| hir::ConstContext::Const | hir::ConstContext::Static(_) => { |
| let mut cursor = FlowSensitiveAnalysis::new(CustomEq, ccx) |
| .into_engine(ccx.tcx, &ccx.body) |
| .iterate_to_fixpoint() |
| .into_results_cursor(&ccx.body); |
| |
| cursor.seek_after_primary_effect(return_loc); |
| cursor.contains(RETURN_PLACE) |
| } |
| }; |
| |
| ConstQualifs { |
| needs_drop: self.needs_drop(ccx, RETURN_PLACE, return_loc), |
| has_mut_interior: self.has_mut_interior(ccx, RETURN_PLACE, return_loc), |
| custom_eq, |
| error_occured, |
| } |
| } |
| } |
| |
| pub struct Checker<'mir, 'tcx> { |
| ccx: &'mir ConstCx<'mir, 'tcx>, |
| qualifs: Qualifs<'mir, 'tcx>, |
| |
| /// The span of the current statement. |
| span: Span, |
| |
| /// A set that stores for each local whether it has a `StorageDead` for it somewhere. |
| local_has_storage_dead: Option<BitSet<Local>>, |
| |
| error_emitted: Option<ErrorReported>, |
| secondary_errors: Vec<Diagnostic>, |
| } |
| |
| impl Deref for Checker<'mir, 'tcx> { |
| type Target = ConstCx<'mir, 'tcx>; |
| |
| fn deref(&self) -> &Self::Target { |
| &self.ccx |
| } |
| } |
| |
| impl Checker<'mir, 'tcx> { |
| pub fn new(ccx: &'mir ConstCx<'mir, 'tcx>) -> Self { |
| Checker { |
| span: ccx.body.span, |
| ccx, |
| qualifs: Default::default(), |
| local_has_storage_dead: None, |
| error_emitted: None, |
| secondary_errors: Vec::new(), |
| } |
| } |
| |
| pub fn check_body(&mut self) { |
| let ConstCx { tcx, body, .. } = *self.ccx; |
| let def_id = self.ccx.def_id(); |
| |
| // `async` functions cannot be `const fn`. This is checked during AST lowering, so there's |
| // no need to emit duplicate errors here. |
| if is_async_fn(self.ccx) || body.generator.is_some() { |
| tcx.sess.delay_span_bug(body.span, "`async` functions cannot be `const fn`"); |
| return; |
| } |
| |
| // The local type and predicate checks are not free and only relevant for `const fn`s. |
| if self.const_kind() == hir::ConstContext::ConstFn { |
| // Prevent const trait methods from being annotated as `stable`. |
| // FIXME: Do this as part of stability checking. |
| if self.is_const_stable_const_fn() { |
| let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); |
| if crate::const_eval::is_parent_const_impl_raw(tcx, hir_id) { |
| self.ccx |
| .tcx |
| .sess |
| .struct_span_err(self.span, "trait methods cannot be stable const fn") |
| .emit(); |
| } |
| } |
| |
| self.check_item_predicates(); |
| |
| for (idx, local) in body.local_decls.iter_enumerated() { |
| // Handle the return place below. |
| if idx == RETURN_PLACE || local.internal { |
| continue; |
| } |
| |
| self.span = local.source_info.span; |
| self.check_local_or_return_ty(local.ty, idx); |
| } |
| |
| // impl trait is gone in MIR, so check the return type of a const fn by its signature |
| // instead of the type of the return place. |
| self.span = body.local_decls[RETURN_PLACE].source_info.span; |
| let return_ty = tcx.fn_sig(def_id).output(); |
| self.check_local_or_return_ty(return_ty.skip_binder(), RETURN_PLACE); |
| } |
| |
| self.visit_body(&body); |
| |
| // Ensure that the end result is `Sync` in a non-thread local `static`. |
| let should_check_for_sync = self.const_kind() |
| == hir::ConstContext::Static(hir::Mutability::Not) |
| && !tcx.is_thread_local_static(def_id.to_def_id()); |
| |
| if should_check_for_sync { |
| let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); |
| check_return_ty_is_sync(tcx, &body, hir_id); |
| } |
| |
| // If we got through const-checking without emitting any "primary" errors, emit any |
| // "secondary" errors if they occurred. |
| let secondary_errors = mem::take(&mut self.secondary_errors); |
| if self.error_emitted.is_none() { |
| for error in secondary_errors { |
| self.tcx.sess.diagnostic().emit_diagnostic(&error); |
| } |
| } else { |
| assert!(self.tcx.sess.has_errors()); |
| } |
| } |
| |
| fn local_has_storage_dead(&mut self, local: Local) -> bool { |
| let ccx = self.ccx; |
| self.local_has_storage_dead |
| .get_or_insert_with(|| { |
| struct StorageDeads { |
| locals: BitSet<Local>, |
| } |
| impl Visitor<'tcx> for StorageDeads { |
| fn visit_statement(&mut self, stmt: &Statement<'tcx>, _: Location) { |
| if let StatementKind::StorageDead(l) = stmt.kind { |
| self.locals.insert(l); |
| } |
| } |
| } |
| let mut v = StorageDeads { locals: BitSet::new_empty(ccx.body.local_decls.len()) }; |
| v.visit_body(ccx.body); |
| v.locals |
| }) |
| .contains(local) |
| } |
| |
| pub fn qualifs_in_return_place(&mut self) -> ConstQualifs { |
| self.qualifs.in_return_place(self.ccx, self.error_emitted) |
| } |
| |
| /// Emits an error if an expression cannot be evaluated in the current context. |
| pub fn check_op(&mut self, op: impl NonConstOp) { |
| self.check_op_spanned(op, self.span); |
| } |
| |
| /// Emits an error at the given `span` if an expression cannot be evaluated in the current |
| /// context. |
| pub fn check_op_spanned<O: NonConstOp>(&mut self, op: O, span: Span) { |
| let gate = match op.status_in_item(self.ccx) { |
| Status::Allowed => return, |
| |
| Status::Unstable(gate) if self.tcx.features().enabled(gate) => { |
| let unstable_in_stable = self.ccx.is_const_stable_const_fn() |
| && !super::rustc_allow_const_fn_unstable( |
| self.tcx, |
| self.def_id().to_def_id(), |
| gate, |
| ); |
| if unstable_in_stable { |
| emit_unstable_in_stable_error(self.ccx, span, gate); |
| } |
| |
| return; |
| } |
| |
| Status::Unstable(gate) => Some(gate), |
| Status::Forbidden => None, |
| }; |
| |
| if self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you { |
| self.tcx.sess.miri_unleashed_feature(span, gate); |
| return; |
| } |
| |
| let mut err = op.build_error(self.ccx, span); |
| assert!(err.is_error()); |
| |
| match op.importance() { |
| ops::DiagnosticImportance::Primary => { |
| self.error_emitted = Some(ErrorReported); |
| err.emit(); |
| } |
| |
| ops::DiagnosticImportance::Secondary => err.buffer(&mut self.secondary_errors), |
| } |
| } |
| |
| fn check_static(&mut self, def_id: DefId, span: Span) { |
| if self.tcx.is_thread_local_static(def_id) { |
| self.tcx.sess.delay_span_bug(span, "tls access is checked in `Rvalue::ThreadLocalRef"); |
| } |
| self.check_op_spanned(ops::StaticAccess, span) |
| } |
| |
| fn check_local_or_return_ty(&mut self, ty: Ty<'tcx>, local: Local) { |
| let kind = self.body.local_kind(local); |
| |
| for ty in ty.walk(self.tcx) { |
| let ty = match ty.unpack() { |
| GenericArgKind::Type(ty) => ty, |
| |
| // No constraints on lifetimes or constants, except potentially |
| // constants' types, but `walk` will get to them as well. |
| GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => continue, |
| }; |
| |
| match *ty.kind() { |
| ty::Ref(_, _, hir::Mutability::Mut) => self.check_op(ops::ty::MutRef(kind)), |
| ty::Opaque(..) => self.check_op(ops::ty::ImplTrait), |
| ty::FnPtr(..) => self.check_op(ops::ty::FnPtr(kind)), |
| |
| ty::Dynamic(preds, _) => { |
| for pred in preds.iter() { |
| match pred.skip_binder() { |
| ty::ExistentialPredicate::AutoTrait(_) |
| | ty::ExistentialPredicate::Projection(_) => { |
| self.check_op(ops::ty::TraitBound(kind)) |
| } |
| ty::ExistentialPredicate::Trait(trait_ref) => { |
| if Some(trait_ref.def_id) != self.tcx.lang_items().sized_trait() { |
| self.check_op(ops::ty::TraitBound(kind)) |
| } |
| } |
| } |
| } |
| } |
| _ => {} |
| } |
| } |
| } |
| |
| fn check_item_predicates(&mut self) { |
| let ConstCx { tcx, .. } = *self.ccx; |
| |
| let mut current = self.def_id().to_def_id(); |
| loop { |
| let predicates = tcx.predicates_of(current); |
| for (predicate, _) in predicates.predicates { |
| match predicate.kind().skip_binder() { |
| ty::PredicateKind::RegionOutlives(_) |
| | ty::PredicateKind::TypeOutlives(_) |
| | ty::PredicateKind::WellFormed(_) |
| | ty::PredicateKind::Projection(_) |
| | ty::PredicateKind::ConstEvaluatable(..) |
| | ty::PredicateKind::ConstEquate(..) |
| | ty::PredicateKind::TypeWellFormedFromEnv(..) => continue, |
| ty::PredicateKind::ObjectSafe(_) => { |
| bug!("object safe predicate on function: {:#?}", predicate) |
| } |
| ty::PredicateKind::ClosureKind(..) => { |
| bug!("closure kind predicate on function: {:#?}", predicate) |
| } |
| ty::PredicateKind::Subtype(_) | ty::PredicateKind::Coerce(_) => { |
| bug!("subtype/coerce predicate on function: {:#?}", predicate) |
| } |
| ty::PredicateKind::Trait(pred) => { |
| if Some(pred.def_id()) == tcx.lang_items().sized_trait() { |
| continue; |
| } |
| match pred.self_ty().kind() { |
| ty::Param(p) => { |
| let generics = tcx.generics_of(current); |
| let def = generics.type_param(p, tcx); |
| let span = tcx.def_span(def.def_id); |
| |
| // These are part of the function signature, so treat them like |
| // arguments when determining importance. |
| let kind = LocalKind::Arg; |
| |
| self.check_op_spanned(ops::ty::TraitBound(kind), span); |
| } |
| // other kinds of bounds are either tautologies |
| // or cause errors in other passes |
| _ => continue, |
| } |
| } |
| } |
| } |
| match predicates.parent { |
| Some(parent) => current = parent, |
| None => break, |
| } |
| } |
| } |
| |
| fn check_mut_borrow(&mut self, local: Local, kind: hir::BorrowKind) { |
| match self.const_kind() { |
| // In a const fn all borrows are transient or point to the places given via |
| // references in the arguments (so we already checked them with |
| // TransientMutBorrow/MutBorrow as appropriate). |
| // The borrow checker guarantees that no new non-transient borrows are created. |
| // NOTE: Once we have heap allocations during CTFE we need to figure out |
| // how to prevent `const fn` to create long-lived allocations that point |
| // to mutable memory. |
| hir::ConstContext::ConstFn => self.check_op(ops::TransientMutBorrow(kind)), |
| _ => { |
| // Locals with StorageDead do not live beyond the evaluation and can |
| // thus safely be borrowed without being able to be leaked to the final |
| // value of the constant. |
| if self.local_has_storage_dead(local) { |
| self.check_op(ops::TransientMutBorrow(kind)); |
| } else { |
| self.check_op(ops::MutBorrow(kind)); |
| } |
| } |
| } |
| } |
| } |
| |
| impl Visitor<'tcx> for Checker<'mir, 'tcx> { |
| fn visit_basic_block_data(&mut self, bb: BasicBlock, block: &BasicBlockData<'tcx>) { |
| trace!("visit_basic_block_data: bb={:?} is_cleanup={:?}", bb, block.is_cleanup); |
| |
| // We don't const-check basic blocks on the cleanup path since we never unwind during |
| // const-eval: a panic causes an immediate compile error. In other words, cleanup blocks |
| // are unreachable during const-eval. |
| // |
| // We can't be more conservative (e.g., by const-checking cleanup blocks anyways) because |
| // locals that would never be dropped during normal execution are sometimes dropped during |
| // unwinding, which means backwards-incompatible live-drop errors. |
| if block.is_cleanup { |
| return; |
| } |
| |
| self.super_basic_block_data(bb, block); |
| } |
| |
| fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { |
| trace!("visit_rvalue: rvalue={:?} location={:?}", rvalue, location); |
| |
| // Special-case reborrows to be more like a copy of a reference. |
| match *rvalue { |
| Rvalue::Ref(_, kind, place) => { |
| if let Some(reborrowed_place_ref) = place_as_reborrow(self.tcx, self.body, place) { |
| let ctx = match kind { |
| BorrowKind::Shared => { |
| PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow) |
| } |
| BorrowKind::Shallow => { |
| PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow) |
| } |
| BorrowKind::Unique => { |
| PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow) |
| } |
| BorrowKind::Mut { .. } => { |
| PlaceContext::MutatingUse(MutatingUseContext::Borrow) |
| } |
| }; |
| self.visit_local(&reborrowed_place_ref.local, ctx, location); |
| self.visit_projection(reborrowed_place_ref, ctx, location); |
| return; |
| } |
| } |
| Rvalue::AddressOf(mutbl, place) => { |
| if let Some(reborrowed_place_ref) = place_as_reborrow(self.tcx, self.body, place) { |
| let ctx = match mutbl { |
| Mutability::Not => { |
| PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) |
| } |
| Mutability::Mut => PlaceContext::MutatingUse(MutatingUseContext::AddressOf), |
| }; |
| self.visit_local(&reborrowed_place_ref.local, ctx, location); |
| self.visit_projection(reborrowed_place_ref, ctx, location); |
| return; |
| } |
| } |
| _ => {} |
| } |
| |
| self.super_rvalue(rvalue, location); |
| |
| match *rvalue { |
| Rvalue::ThreadLocalRef(_) => self.check_op(ops::ThreadLocalAccess), |
| |
| Rvalue::Use(_) |
| | Rvalue::Repeat(..) |
| | Rvalue::Discriminant(..) |
| | Rvalue::Len(_) |
| | Rvalue::Aggregate(..) => {} |
| |
| Rvalue::Ref(_, kind @ BorrowKind::Mut { .. }, ref place) |
| | Rvalue::Ref(_, kind @ BorrowKind::Unique, ref place) => { |
| let ty = place.ty(self.body, self.tcx).ty; |
| let is_allowed = match ty.kind() { |
| // Inside a `static mut`, `&mut [...]` is allowed. |
| ty::Array(..) | ty::Slice(_) |
| if self.const_kind() == hir::ConstContext::Static(hir::Mutability::Mut) => |
| { |
| true |
| } |
| |
| // FIXME(ecstaticmorse): We could allow `&mut []` inside a const context given |
| // that this is merely a ZST and it is already eligible for promotion. |
| // This may require an RFC? |
| /* |
| ty::Array(_, len) if len.try_eval_usize(cx.tcx, cx.param_env) == Some(0) |
| => true, |
| */ |
| _ => false, |
| }; |
| |
| if !is_allowed { |
| if let BorrowKind::Mut { .. } = kind { |
| self.check_mut_borrow(place.local, hir::BorrowKind::Ref) |
| } else { |
| self.check_op(ops::CellBorrow); |
| } |
| } |
| } |
| |
| Rvalue::AddressOf(Mutability::Mut, ref place) => { |
| self.check_mut_borrow(place.local, hir::BorrowKind::Raw) |
| } |
| |
| Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Shallow, ref place) |
| | Rvalue::AddressOf(Mutability::Not, ref place) => { |
| let borrowed_place_has_mut_interior = qualifs::in_place::<HasMutInterior, _>( |
| &self.ccx, |
| &mut |local| self.qualifs.has_mut_interior(self.ccx, local, location), |
| place.as_ref(), |
| ); |
| |
| if borrowed_place_has_mut_interior { |
| match self.const_kind() { |
| // In a const fn all borrows are transient or point to the places given via |
| // references in the arguments (so we already checked them with |
| // TransientCellBorrow/CellBorrow as appropriate). |
| // The borrow checker guarantees that no new non-transient borrows are created. |
| // NOTE: Once we have heap allocations during CTFE we need to figure out |
| // how to prevent `const fn` to create long-lived allocations that point |
| // to (interior) mutable memory. |
| hir::ConstContext::ConstFn => self.check_op(ops::TransientCellBorrow), |
| _ => { |
| // Locals with StorageDead are definitely not part of the final constant value, and |
| // it is thus inherently safe to permit such locals to have their |
| // address taken as we can't end up with a reference to them in the |
| // final value. |
| // Note: This is only sound if every local that has a `StorageDead` has a |
| // `StorageDead` in every control flow path leading to a `return` terminator. |
| if self.local_has_storage_dead(place.local) { |
| self.check_op(ops::TransientCellBorrow); |
| } else { |
| self.check_op(ops::CellBorrow); |
| } |
| } |
| } |
| } |
| } |
| |
| Rvalue::Cast( |
| CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer), |
| _, |
| _, |
| ) => {} |
| |
| Rvalue::Cast( |
| CastKind::Pointer( |
| PointerCast::UnsafeFnPointer |
| | PointerCast::ClosureFnPointer(_) |
| | PointerCast::ReifyFnPointer, |
| ), |
| _, |
| _, |
| ) => self.check_op(ops::FnPtrCast), |
| |
| Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), _, _) => { |
| // Nothing to check here (`check_local_or_return_ty` ensures no trait objects occur |
| // in the type of any local, which also excludes casts). |
| } |
| |
| Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) => { |
| let operand_ty = operand.ty(self.body, self.tcx); |
| let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast"); |
| let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast"); |
| |
| if let (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) = (cast_in, cast_out) { |
| self.check_op(ops::RawPtrToIntCast); |
| } |
| } |
| |
| Rvalue::NullaryOp(NullOp::SizeOf, _) => {} |
| Rvalue::NullaryOp(NullOp::Box, _) => self.check_op(ops::HeapAllocation), |
| |
| Rvalue::UnaryOp(_, ref operand) => { |
| let ty = operand.ty(self.body, self.tcx); |
| if is_int_bool_or_char(ty) { |
| // Int, bool, and char operations are fine. |
| } else if ty.is_floating_point() { |
| self.check_op(ops::FloatingPointOp); |
| } else { |
| span_bug!(self.span, "non-primitive type in `Rvalue::UnaryOp`: {:?}", ty); |
| } |
| } |
| |
| Rvalue::BinaryOp(op, box (ref lhs, ref rhs)) |
| | Rvalue::CheckedBinaryOp(op, box (ref lhs, ref rhs)) => { |
| let lhs_ty = lhs.ty(self.body, self.tcx); |
| let rhs_ty = rhs.ty(self.body, self.tcx); |
| |
| if is_int_bool_or_char(lhs_ty) && is_int_bool_or_char(rhs_ty) { |
| // Int, bool, and char operations are fine. |
| } else if lhs_ty.is_fn_ptr() || lhs_ty.is_unsafe_ptr() { |
| assert_eq!(lhs_ty, rhs_ty); |
| assert!( |
| op == BinOp::Eq |
| || op == BinOp::Ne |
| || op == BinOp::Le |
| || op == BinOp::Lt |
| || op == BinOp::Ge |
| || op == BinOp::Gt |
| || op == BinOp::Offset |
| ); |
| |
| self.check_op(ops::RawPtrComparison); |
| } else if lhs_ty.is_floating_point() || rhs_ty.is_floating_point() { |
| self.check_op(ops::FloatingPointOp); |
| } else { |
| span_bug!( |
| self.span, |
| "non-primitive type in `Rvalue::BinaryOp`: {:?} ⚬ {:?}", |
| lhs_ty, |
| rhs_ty |
| ); |
| } |
| } |
| } |
| } |
| |
| fn visit_operand(&mut self, op: &Operand<'tcx>, location: Location) { |
| self.super_operand(op, location); |
| if let Operand::Constant(c) = op { |
| if let Some(def_id) = c.check_static_ptr(self.tcx) { |
| self.check_static(def_id, self.span); |
| } |
| } |
| } |
| fn visit_projection_elem( |
| &mut self, |
| place_local: Local, |
| proj_base: &[PlaceElem<'tcx>], |
| elem: PlaceElem<'tcx>, |
| context: PlaceContext, |
| location: Location, |
| ) { |
| trace!( |
| "visit_projection_elem: place_local={:?} proj_base={:?} elem={:?} \ |
| context={:?} location={:?}", |
| place_local, |
| proj_base, |
| elem, |
| context, |
| location, |
| ); |
| |
| self.super_projection_elem(place_local, proj_base, elem, context, location); |
| |
| match elem { |
| ProjectionElem::Deref => { |
| let base_ty = Place::ty_from(place_local, proj_base, self.body, self.tcx).ty; |
| if let ty::RawPtr(_) = base_ty.kind() { |
| if proj_base.is_empty() { |
| let decl = &self.body.local_decls[place_local]; |
| if let Some(box LocalInfo::StaticRef { def_id, .. }) = decl.local_info { |
| let span = decl.source_info.span; |
| self.check_static(def_id, span); |
| return; |
| } |
| } |
| self.check_op(ops::RawPtrDeref); |
| } |
| |
| if context.is_mutating_use() { |
| self.check_op(ops::MutDeref); |
| } |
| } |
| |
| ProjectionElem::ConstantIndex { .. } |
| | ProjectionElem::Downcast(..) |
| | ProjectionElem::Subslice { .. } |
| | ProjectionElem::Field(..) |
| | ProjectionElem::Index(_) => {} |
| } |
| } |
| |
| fn visit_source_info(&mut self, source_info: &SourceInfo) { |
| trace!("visit_source_info: source_info={:?}", source_info); |
| self.span = source_info.span; |
| } |
| |
| fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { |
| trace!("visit_statement: statement={:?} location={:?}", statement, location); |
| |
| self.super_statement(statement, location); |
| |
| match statement.kind { |
| StatementKind::LlvmInlineAsm { .. } => { |
| self.check_op(ops::InlineAsm); |
| } |
| |
| StatementKind::Assign(..) |
| | StatementKind::SetDiscriminant { .. } |
| | StatementKind::FakeRead(..) |
| | StatementKind::StorageLive(_) |
| | StatementKind::StorageDead(_) |
| | StatementKind::Retag { .. } |
| | StatementKind::AscribeUserType(..) |
| | StatementKind::Coverage(..) |
| | StatementKind::CopyNonOverlapping(..) |
| | StatementKind::Nop => {} |
| } |
| } |
| |
| #[instrument(level = "debug", skip(self))] |
| fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) { |
| use rustc_target::spec::abi::Abi::RustIntrinsic; |
| |
| self.super_terminator(terminator, location); |
| |
| match &terminator.kind { |
| TerminatorKind::Call { func, args, .. } => { |
| let ConstCx { tcx, body, param_env, .. } = *self.ccx; |
| let caller = self.def_id().to_def_id(); |
| |
| let fn_ty = func.ty(body, tcx); |
| |
| let (mut callee, mut substs) = match *fn_ty.kind() { |
| ty::FnDef(def_id, substs) => (def_id, substs), |
| |
| ty::FnPtr(_) => { |
| self.check_op(ops::FnCallIndirect); |
| return; |
| } |
| _ => { |
| span_bug!(terminator.source_info.span, "invalid callee of type {:?}", fn_ty) |
| } |
| }; |
| |
| let mut nonconst_call_permission = false; |
| |
| // Attempting to call a trait method? |
| if let Some(trait_id) = tcx.trait_of_item(callee) { |
| trace!("attempting to call a trait method"); |
| if !self.tcx.features().const_trait_impl { |
| self.check_op(ops::FnCallNonConst); |
| return; |
| } |
| |
| let trait_ref = TraitRef::from_method(tcx, trait_id, substs); |
| let obligation = Obligation::new( |
| ObligationCause::dummy(), |
| param_env, |
| Binder::dummy(TraitPredicate { |
| trait_ref, |
| constness: ty::BoundConstness::ConstIfConst, |
| }), |
| ); |
| |
| let implsrc = tcx.infer_ctxt().enter(|infcx| { |
| let mut selcx = |
| SelectionContext::with_constness(&infcx, hir::Constness::Const); |
| selcx.select(&obligation) |
| }); |
| |
| match implsrc { |
| Ok(Some(ImplSource::Param(_, ty::BoundConstness::ConstIfConst))) => { |
| debug!( |
| "const_trait_impl: provided {:?} via where-clause in {:?}", |
| trait_ref, param_env |
| ); |
| return; |
| } |
| Ok(Some(ImplSource::UserDefined(data))) => { |
| let callee_name = tcx.item_name(callee); |
| if let Some(&did) = tcx |
| .associated_item_def_ids(data.impl_def_id) |
| .iter() |
| .find(|did| tcx.item_name(**did) == callee_name) |
| { |
| // using internal substs is ok here, since this is only |
| // used for the `resolve` call below |
| substs = InternalSubsts::identity_for_item(tcx, did); |
| callee = did; |
| } |
| } |
| _ if !tcx.is_const_fn_raw(callee) => { |
| // At this point, it is only legal when the caller is marked with |
| // #[default_method_body_is_const], and the callee is in the same |
| // trait. |
| let callee_trait = tcx.trait_of_item(callee); |
| if callee_trait.is_some() { |
| if tcx.has_attr(caller, sym::default_method_body_is_const) { |
| if tcx.trait_of_item(caller) == callee_trait { |
| nonconst_call_permission = true; |
| } |
| } |
| } |
| |
| if !nonconst_call_permission { |
| self.check_op(ops::FnCallNonConst); |
| return; |
| } |
| } |
| _ => {} |
| } |
| |
| // Resolve a trait method call to its concrete implementation, which may be in a |
| // `const` trait impl. |
| let instance = Instance::resolve(tcx, param_env, callee, substs); |
| debug!("Resolving ({:?}) -> {:?}", callee, instance); |
| if let Ok(Some(func)) = instance { |
| if let InstanceDef::Item(def) = func.def { |
| callee = def.did; |
| } |
| } |
| } |
| |
| // At this point, we are calling a function, `callee`, whose `DefId` is known... |
| if is_lang_panic_fn(tcx, callee) { |
| self.check_op(ops::Panic); |
| |
| // const-eval of the `begin_panic` fn assumes the argument is `&str` |
| if Some(callee) == tcx.lang_items().begin_panic_fn() { |
| match args[0].ty(&self.ccx.body.local_decls, tcx).kind() { |
| ty::Ref(_, ty, _) if ty.is_str() => (), |
| _ => self.check_op(ops::PanicNonStr), |
| } |
| } |
| |
| return; |
| } |
| |
| // `async` blocks get lowered to `std::future::from_generator(/* a closure */)`. |
| let is_async_block = Some(callee) == tcx.lang_items().from_generator_fn(); |
| if is_async_block { |
| let kind = hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block); |
| self.check_op(ops::Generator(kind)); |
| return; |
| } |
| |
| let is_intrinsic = tcx.fn_sig(callee).abi() == RustIntrinsic; |
| |
| if !tcx.is_const_fn_raw(callee) { |
| if tcx.trait_of_item(callee).is_some() { |
| if tcx.has_attr(callee, sym::default_method_body_is_const) { |
| // To get to here we must have already found a const impl for the |
| // trait, but for it to still be non-const can be that the impl is |
| // using default method bodies. |
| nonconst_call_permission = true; |
| } |
| } |
| |
| if !nonconst_call_permission { |
| self.check_op(ops::FnCallNonConst); |
| return; |
| } |
| } |
| |
| // If the `const fn` we are trying to call is not const-stable, ensure that we have |
| // the proper feature gate enabled. |
| if let Some(gate) = is_unstable_const_fn(tcx, callee) { |
| trace!(?gate, "calling unstable const fn"); |
| if self.span.allows_unstable(gate) { |
| return; |
| } |
| |
| // Calling an unstable function *always* requires that the corresponding gate |
| // be enabled, even if the function has `#[rustc_allow_const_fn_unstable(the_gate)]`. |
| if !tcx.features().declared_lib_features.iter().any(|&(sym, _)| sym == gate) { |
| self.check_op(ops::FnCallUnstable(callee, Some(gate))); |
| return; |
| } |
| |
| // If this crate is not using stability attributes, or the caller is not claiming to be a |
| // stable `const fn`, that is all that is required. |
| if !self.ccx.is_const_stable_const_fn() { |
| trace!("crate not using stability attributes or caller not stably const"); |
| return; |
| } |
| |
| // Otherwise, we are something const-stable calling a const-unstable fn. |
| |
| if super::rustc_allow_const_fn_unstable(tcx, caller, gate) { |
| trace!("rustc_allow_const_fn_unstable gate active"); |
| return; |
| } |
| |
| self.check_op(ops::FnCallUnstable(callee, Some(gate))); |
| return; |
| } |
| |
| // FIXME(ecstaticmorse); For compatibility, we consider `unstable` callees that |
| // have no `rustc_const_stable` attributes to be const-unstable as well. This |
| // should be fixed later. |
| let callee_is_unstable_unmarked = tcx.lookup_const_stability(callee).is_none() |
| && tcx.lookup_stability(callee).map_or(false, |s| s.level.is_unstable()); |
| if callee_is_unstable_unmarked { |
| trace!("callee_is_unstable_unmarked"); |
| // We do not use `const` modifiers for intrinsic "functions", as intrinsics are |
| // `extern` funtions, and these have no way to get marked `const`. So instead we |
| // use `rustc_const_(un)stable` attributes to mean that the intrinsic is `const` |
| if self.ccx.is_const_stable_const_fn() || is_intrinsic { |
| self.check_op(ops::FnCallUnstable(callee, None)); |
| return; |
| } |
| } |
| trace!("permitting call"); |
| } |
| |
| // Forbid all `Drop` terminators unless the place being dropped is a local with no |
| // projections that cannot be `NeedsDrop`. |
| TerminatorKind::Drop { place: dropped_place, .. } |
| | TerminatorKind::DropAndReplace { place: dropped_place, .. } => { |
| // If we are checking live drops after drop-elaboration, don't emit duplicate |
| // errors here. |
| if super::post_drop_elaboration::checking_enabled(self.ccx) { |
| return; |
| } |
| |
| let mut err_span = self.span; |
| |
| // Check to see if the type of this place can ever have a drop impl. If not, this |
| // `Drop` terminator is frivolous. |
| let ty_needs_drop = |
| dropped_place.ty(self.body, self.tcx).ty.needs_drop(self.tcx, self.param_env); |
| |
| if !ty_needs_drop { |
| return; |
| } |
| |
| let needs_drop = if let Some(local) = dropped_place.as_local() { |
| // Use the span where the local was declared as the span of the drop error. |
| err_span = self.body.local_decls[local].source_info.span; |
| self.qualifs.needs_drop(self.ccx, local, location) |
| } else { |
| true |
| }; |
| |
| if needs_drop { |
| self.check_op_spanned( |
| ops::LiveDrop { dropped_at: Some(terminator.source_info.span) }, |
| err_span, |
| ); |
| } |
| } |
| |
| TerminatorKind::InlineAsm { .. } => self.check_op(ops::InlineAsm), |
| |
| TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => { |
| self.check_op(ops::Generator(hir::GeneratorKind::Gen)) |
| } |
| |
| TerminatorKind::Abort => { |
| // Cleanup blocks are skipped for const checking (see `visit_basic_block_data`). |
| span_bug!(self.span, "`Abort` terminator outside of cleanup block") |
| } |
| |
| TerminatorKind::Assert { .. } |
| | TerminatorKind::FalseEdge { .. } |
| | TerminatorKind::FalseUnwind { .. } |
| | TerminatorKind::Goto { .. } |
| | TerminatorKind::Resume |
| | TerminatorKind::Return |
| | TerminatorKind::SwitchInt { .. } |
| | TerminatorKind::Unreachable => {} |
| } |
| } |
| } |
| |
| fn check_return_ty_is_sync(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, hir_id: HirId) { |
| let ty = body.return_ty(); |
| tcx.infer_ctxt().enter(|infcx| { |
| let cause = traits::ObligationCause::new(body.span, hir_id, traits::SharedStatic); |
| let mut fulfillment_cx = traits::FulfillmentContext::new(); |
| let sync_def_id = tcx.require_lang_item(LangItem::Sync, Some(body.span)); |
| fulfillment_cx.register_bound(&infcx, ty::ParamEnv::empty(), ty, sync_def_id, cause); |
| if let Err(err) = fulfillment_cx.select_all_or_error(&infcx) { |
| infcx.report_fulfillment_errors(&err, None, false); |
| } |
| }); |
| } |
| |
| fn place_as_reborrow( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| place: Place<'tcx>, |
| ) -> Option<PlaceRef<'tcx>> { |
| match place.as_ref().last_projection() { |
| Some((place_base, ProjectionElem::Deref)) => { |
| // A borrow of a `static` also looks like `&(*_1)` in the MIR, but `_1` is a `const` |
| // that points to the allocation for the static. Don't treat these as reborrows. |
| if body.local_decls[place_base.local].is_ref_to_static() { |
| None |
| } else { |
| // Ensure the type being derefed is a reference and not a raw pointer. |
| // This is sufficient to prevent an access to a `static mut` from being marked as a |
| // reborrow, even if the check above were to disappear. |
| let inner_ty = place_base.ty(body, tcx).ty; |
| |
| if let ty::Ref(..) = inner_ty.kind() { |
| return Some(place_base); |
| } else { |
| return None; |
| } |
| } |
| } |
| _ => None, |
| } |
| } |
| |
| fn is_int_bool_or_char(ty: Ty<'_>) -> bool { |
| ty.is_bool() || ty.is_integral() || ty.is_char() |
| } |
| |
| fn is_async_fn(ccx: &ConstCx<'_, '_>) -> bool { |
| ccx.fn_sig().map_or(false, |sig| sig.header.asyncness == hir::IsAsync::Async) |
| } |
| |
| fn emit_unstable_in_stable_error(ccx: &ConstCx<'_, '_>, span: Span, gate: Symbol) { |
| let attr_span = ccx.fn_sig().map_or(ccx.body.span, |sig| sig.span.shrink_to_lo()); |
| |
| ccx.tcx |
| .sess |
| .struct_span_err( |
| span, |
| &format!("const-stable function cannot use `#[feature({})]`", gate.as_str()), |
| ) |
| .span_suggestion( |
| attr_span, |
| "if it is not part of the public API, make this function unstably const", |
| concat!(r#"#[rustc_const_unstable(feature = "...", issue = "...")]"#, '\n').to_owned(), |
| Applicability::HasPlaceholders, |
| ) |
| .span_suggestion( |
| attr_span, |
| "otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks", |
| format!("#[rustc_allow_const_fn_unstable({})]\n", gate), |
| Applicability::MaybeIncorrect, |
| ) |
| .emit(); |
| } |
