use rustc_hir::def_id::DefId;
use rustc_middle::mir::patch::MirPatch;
use rustc_middle::mir::visit::MutVisitor;
use rustc_middle::mir::*;
use rustc_middle::span_bug;
use rustc_middle::ty::{Ty, TyCtxt};
use rustc_target::abi::FieldIdx;
pub fn build_ptr_tys<'tcx>(
tcx: TyCtxt<'tcx>,
pointee: Ty<'tcx>,
unique_did: DefId,
nonnull_did: DefId,
) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
let args = tcx.mk_args(&[pointee.into()]);
let unique_ty = tcx.type_of(unique_did).instantiate(tcx, args);
let nonnull_ty = tcx.type_of(nonnull_did).instantiate(tcx, args);
let ptr_ty = Ty::new_imm_ptr(tcx, pointee);
(unique_ty, nonnull_ty, ptr_ty)
}
pub fn build_projection<'tcx>(
unique_ty: Ty<'tcx>,
nonnull_ty: Ty<'tcx>,
ptr_ty: Ty<'tcx>,
) -> [PlaceElem<'tcx>; 3] {
[
PlaceElem::Field(FieldIdx::ZERO, unique_ty),
PlaceElem::Field(FieldIdx::ZERO, nonnull_ty),
PlaceElem::Field(FieldIdx::ZERO, ptr_ty),
]
}
struct ElaborateBoxDerefVisitor<'tcx, 'a> {
tcx: TyCtxt<'tcx>,
unique_did: DefId,
nonnull_did: DefId,
local_decls: &'a mut LocalDecls<'tcx>,
patch: MirPatch<'tcx>,
}
impl<'tcx, 'a> MutVisitor<'tcx> for ElaborateBoxDerefVisitor<'tcx, 'a> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn visit_place(
&mut self,
place: &mut Place<'tcx>,
context: visit::PlaceContext,
location: Location,
) {
let tcx = self.tcx;
let base_ty = self.local_decls[place.local].ty;
if place.projection.first() == Some(&PlaceElem::Deref) && base_ty.is_box() {
let source_info = self.local_decls[place.local].source_info;
let (unique_ty, nonnull_ty, ptr_ty) =
build_ptr_tys(tcx, base_ty.boxed_ty(), self.unique_did, self.nonnull_did);
let ptr_local = self.patch.new_temp(ptr_ty, source_info.span);
self.patch.add_assign(
location,
Place::from(ptr_local),
Rvalue::Use(Operand::Copy(
Place::from(place.local)
.project_deeper(&build_projection(unique_ty, nonnull_ty, ptr_ty), tcx),
)),
);
place.local = ptr_local;
}
self.super_place(place, context, location);
}
}
pub struct ElaborateBoxDerefs;
impl<'tcx> MirPass<'tcx> for ElaborateBoxDerefs {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
if let Some(def_id) = tcx.lang_items().owned_box() {
let unique_did = tcx.adt_def(def_id).non_enum_variant().fields[FieldIdx::ZERO].did;
let Some(nonnull_def) = tcx.type_of(unique_did).instantiate_identity().ty_adt_def()
else {
span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
};
let nonnull_did = nonnull_def.non_enum_variant().fields[FieldIdx::ZERO].did;
let patch = MirPatch::new(body);
let local_decls = &mut body.local_decls;
let mut visitor =
ElaborateBoxDerefVisitor { tcx, unique_did, nonnull_did, local_decls, patch };
for (block, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
visitor.visit_basic_block_data(block, data);
}
visitor.patch.apply(body);
for debug_info in body.var_debug_info.iter_mut() {
if let VarDebugInfoContents::Place(place) = &mut debug_info.value {
let mut new_projections: Option<Vec<_>> = None;
for (base, elem) in place.iter_projections() {
let base_ty = base.ty(&body.local_decls, tcx).ty;
if elem == PlaceElem::Deref && base_ty.is_box() {
let new_projections =
new_projections.get_or_insert_with(|| base.projection.to_vec());
let (unique_ty, nonnull_ty, ptr_ty) =
build_ptr_tys(tcx, base_ty.boxed_ty(), unique_did, nonnull_did);
new_projections.extend_from_slice(&build_projection(
unique_ty, nonnull_ty, ptr_ty,
));
new_projections.push(PlaceElem::Deref);
} else if let Some(new_projections) = new_projections.as_mut() {
new_projections.push(elem);
}
}
if let Some(new_projections) = new_projections {
place.projection = tcx.mk_place_elems(&new_projections);
}
}
}
} else {
}
}
}