Add `CheckLiveDrops` pass
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@ -12,6 +12,7 @@ use rustc_middle::ty::{self, TyCtxt};
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pub use self::qualifs::Qualif;
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mod ops;
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pub mod post_drop_elaboration;
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pub mod qualifs;
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mod resolver;
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pub mod validation;
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@ -0,0 +1,119 @@
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use rustc_hir::def_id::LocalDefId;
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use rustc_middle::mir::visit::Visitor;
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use rustc_middle::mir::{self, BasicBlock, Location};
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use rustc_middle::ty::TyCtxt;
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use rustc_span::Span;
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use super::ops;
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use super::qualifs::{NeedsDrop, Qualif};
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use super::validation::Qualifs;
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use super::ConstCx;
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/// Returns `true` if we should use the more precise live drop checker that runs after drop
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/// elaboration.
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pub fn checking_enabled(tcx: TyCtxt<'tcx>) -> bool {
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tcx.features().const_precise_live_drops
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}
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/// Look for live drops in a const context.
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///
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/// This is separate from the rest of the const checking logic because it must run after drop
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/// elaboration.
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pub fn check_live_drops(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &mir::Body<'tcx>) {
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let const_kind = tcx.hir().body_const_context(def_id);
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if const_kind.is_none() {
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return;
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}
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if !checking_enabled(tcx) {
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return;
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}
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let ccx = ConstCx {
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body,
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tcx,
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def_id: def_id.to_def_id(),
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const_kind,
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param_env: tcx.param_env(def_id),
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};
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let mut visitor = CheckLiveDrops { ccx: &ccx, qualifs: Qualifs::default() };
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visitor.visit_body(body);
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}
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struct CheckLiveDrops<'mir, 'tcx> {
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ccx: &'mir ConstCx<'mir, 'tcx>,
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qualifs: Qualifs<'mir, 'tcx>,
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}
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// So we can access `body` and `tcx`.
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impl std::ops::Deref for CheckLiveDrops<'mir, 'tcx> {
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type Target = ConstCx<'mir, 'tcx>;
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fn deref(&self) -> &Self::Target {
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&self.ccx
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}
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}
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impl CheckLiveDrops<'mir, 'tcx> {
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fn check_live_drop(&self, span: Span) {
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ops::non_const(self.ccx, ops::LiveDrop, span);
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}
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}
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impl Visitor<'tcx> for CheckLiveDrops<'mir, 'tcx> {
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fn visit_basic_block_data(&mut self, bb: BasicBlock, block: &mir::BasicBlockData<'tcx>) {
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trace!("visit_basic_block_data: bb={:?} is_cleanup={:?}", bb, block.is_cleanup);
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// Ignore drop terminators in cleanup blocks.
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if block.is_cleanup {
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return;
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}
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self.super_basic_block_data(bb, block);
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}
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fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) {
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trace!("visit_terminator: terminator={:?} location={:?}", terminator, location);
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match &terminator.kind {
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mir::TerminatorKind::Drop { location: dropped_place, .. } => {
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let dropped_ty = dropped_place.ty(self.body, self.tcx).ty;
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if !NeedsDrop::in_any_value_of_ty(self.ccx, dropped_ty) {
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return;
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}
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if dropped_place.is_indirect() {
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self.check_live_drop(terminator.source_info.span);
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return;
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}
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if self.qualifs.needs_drop(self.ccx, dropped_place.local, location) {
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// Use the span where the dropped local was declared for the error.
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let span = self.body.local_decls[dropped_place.local].source_info.span;
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self.check_live_drop(span);
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}
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}
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mir::TerminatorKind::DropAndReplace { .. } => span_bug!(
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terminator.source_info.span,
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"`DropAndReplace` should be removed by drop elaboration",
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),
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mir::TerminatorKind::Abort
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| mir::TerminatorKind::Call { .. }
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| mir::TerminatorKind::Assert { .. }
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| mir::TerminatorKind::FalseEdge { .. }
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| mir::TerminatorKind::FalseUnwind { .. }
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| mir::TerminatorKind::GeneratorDrop
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| mir::TerminatorKind::Goto { .. }
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| mir::TerminatorKind::InlineAsm { .. }
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| mir::TerminatorKind::Resume
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| mir::TerminatorKind::Return
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| mir::TerminatorKind::SwitchInt { .. }
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| mir::TerminatorKind::Unreachable
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| mir::TerminatorKind::Yield { .. } => {}
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}
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}
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}
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@ -562,6 +562,12 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
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// projections that cannot be `NeedsDrop`.
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TerminatorKind::Drop { location: dropped_place, .. }
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| TerminatorKind::DropAndReplace { location: dropped_place, .. } => {
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// If we are checking live drops after drop-elaboration, don't emit duplicate
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// errors here.
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if super::post_drop_elaboration::checking_enabled(self.tcx) {
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return;
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}
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let mut err_span = self.span;
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// Check to see if the type of this place can ever have a drop impl. If not, this
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