forked from rust-lang/rust
/
post_drop_elaboration.rs
118 lines (97 loc) · 3.99 KB
/
post_drop_elaboration.rs
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use rustc_hir::def_id::LocalDefId;
use rustc_middle::mir::visit::Visitor;
use rustc_middle::mir::{self, BasicBlock, Location};
use rustc_middle::ty::TyCtxt;
use rustc_span::{sym, Span};
use super::ops;
use super::qualifs::{NeedsDrop, Qualif};
use super::validation::Qualifs;
use super::ConstCx;
/// Returns `true` if we should use the more precise live drop checker that runs after drop
/// elaboration.
pub fn checking_enabled(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> bool {
// Const-stable functions must always use the stable live drop checker.
if tcx.features().staged_api && !tcx.has_attr(def_id.to_def_id(), sym::rustc_const_unstable) {
return false;
}
tcx.features().const_precise_live_drops
}
/// Look for live drops in a const context.
///
/// This is separate from the rest of the const checking logic because it must run after drop
/// elaboration.
pub fn check_live_drops(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &mir::Body<'tcx>) {
let const_kind = tcx.hir().body_const_context(def_id);
if const_kind.is_none() {
return;
}
if !checking_enabled(tcx, def_id) {
return;
}
let ccx = ConstCx { body, tcx, def_id, const_kind, param_env: tcx.param_env(def_id) };
let mut visitor = CheckLiveDrops { ccx: &ccx, qualifs: Qualifs::default() };
visitor.visit_body(body);
}
struct CheckLiveDrops<'mir, 'tcx> {
ccx: &'mir ConstCx<'mir, 'tcx>,
qualifs: Qualifs<'mir, 'tcx>,
}
// So we can access `body` and `tcx`.
impl std::ops::Deref for CheckLiveDrops<'mir, 'tcx> {
type Target = ConstCx<'mir, 'tcx>;
fn deref(&self) -> &Self::Target {
&self.ccx
}
}
impl CheckLiveDrops<'mir, 'tcx> {
fn check_live_drop(&self, span: Span) {
ops::non_const(self.ccx, ops::LiveDrop { dropped_at: None }, span);
}
}
impl Visitor<'tcx> for CheckLiveDrops<'mir, 'tcx> {
fn visit_basic_block_data(&mut self, bb: BasicBlock, block: &mir::BasicBlockData<'tcx>) {
trace!("visit_basic_block_data: bb={:?} is_cleanup={:?}", bb, block.is_cleanup);
// Ignore drop terminators in cleanup blocks.
if block.is_cleanup {
return;
}
self.super_basic_block_data(bb, block);
}
fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) {
trace!("visit_terminator: terminator={:?} location={:?}", terminator, location);
match &terminator.kind {
mir::TerminatorKind::Drop { place: dropped_place, .. } => {
let dropped_ty = dropped_place.ty(self.body, self.tcx).ty;
if !NeedsDrop::in_any_value_of_ty(self.ccx, dropped_ty) {
return;
}
if dropped_place.is_indirect() {
self.check_live_drop(terminator.source_info.span);
return;
}
if self.qualifs.needs_drop(self.ccx, dropped_place.local, location) {
// Use the span where the dropped local was declared for the error.
let span = self.body.local_decls[dropped_place.local].source_info.span;
self.check_live_drop(span);
}
}
mir::TerminatorKind::DropAndReplace { .. } => span_bug!(
terminator.source_info.span,
"`DropAndReplace` should be removed by drop elaboration",
),
mir::TerminatorKind::Abort
| mir::TerminatorKind::Call { .. }
| mir::TerminatorKind::Assert { .. }
| mir::TerminatorKind::FalseEdge { .. }
| mir::TerminatorKind::FalseUnwind { .. }
| mir::TerminatorKind::GeneratorDrop
| mir::TerminatorKind::Goto { .. }
| mir::TerminatorKind::InlineAsm { .. }
| mir::TerminatorKind::Resume
| mir::TerminatorKind::Return
| mir::TerminatorKind::SwitchInt { .. }
| mir::TerminatorKind::Unreachable
| mir::TerminatorKind::Yield { .. } => {}
}
}
}