use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
use crate::build::{BlockAnd, BlockAndExtension, Builder};
use crate::thir::*;
+use rustc_hir::def_id::DefId;
+use rustc_hir::HirId;
use rustc_middle::middle::region;
use rustc_middle::mir::AssertKind::BoundsCheck;
use rustc_middle::mir::*;
use rustc_index::vec::Idx;
+/// The "outermost" place that holds this value.
+#[derive(Copy, Clone)]
+pub enum PlaceBase {
+ /// Denotes the start of a `Place`.
+ Local(Local),
+
+ /// When building place for an expression within a closure, the place might start off a
+ /// captured path. When `capture_disjoint_fields` is enabled, we might not know the capture
+ /// index (within the desugared closure) of the captured path until most of the projections
+ /// are applied. We use `PlaceBase::Upvar` to keep track of the root variable off of which the
+ /// captured path starts, the closure the capture belongs to and the trait the closure
+ /// implements.
+ ///
+ /// Once we have figured out the capture index, we can convert the place builder to start from
+ /// `PlaceBase::Local`.
+ ///
+ /// Consider the following example
+ /// ```rust
+ /// let t = (10, (10, (10, 10)));
+ ///
+ /// let c = || {
+ /// println!("{}", t.0.0.0);
+ /// };
+ /// ```
+ /// Here the THIR expression for `t.0.0.0` will be something like
+ ///
+ /// ```
+ /// * Field(0)
+ /// * Field(0)
+ /// * Field(0)
+ /// * UpvarRef(t)
+ /// ```
+ ///
+ /// When `capture_disjoint_fields` is enabled, `t.0.0.0` is captured and we won't be able to
+ /// figure out that it is captured until all the `Field` projections are applied.
+ Upvar {
+ /// HirId of the upvar
+ var_hir_id: HirId,
+ /// DefId of the closure
+ closure_def_id: DefId,
+ /// The trait closure implements, `Fn`, `FnMut`, `FnOnce`
+ closure_kind: ty::ClosureKind },
+}
+
/// `PlaceBuilder` is used to create places during MIR construction. It allows you to "build up" a
/// place by pushing more and more projections onto the end, and then convert the final set into a
/// place using the `into_place` method.
/// and `c` can be progressively pushed onto the place builder that is created when converting `a`.
#[derive(Clone)]
struct PlaceBuilder<'tcx> {
- local: Local,
+ base: PlaceBase,
projection: Vec<PlaceElem<'tcx>>,
}
+fn capture_matching_projections<'a, 'tcx>(
+ typeck_results: &'a ty::TypeckResults<'tcx>,
+ var_hir_id: HirId,
+ closure_def_id: DefId,
+ _projections: &Vec<PlaceElem<'tcx>>,
+) -> Option<(usize, ty::UpvarCapture<'tcx>)> {
+ typeck_results
+ .closure_captures
+ .get(&closure_def_id)
+ .and_then(|captures| captures.get_full(&var_hir_id))
+ .and_then(|(capture_index, _, _)|{
+ let upvar_id = ty::UpvarId::new(var_hir_id, closure_def_id.expect_local());
+ let capture_kind = typeck_results.upvar_capture(upvar_id);
+ Some((capture_index, capture_kind))
+ })
+}
+
+/// Takes a PlaceBuilder and resolves the upvar (if any) within it,
+/// so that the PlaceBuilder now starts from PlaceBase::Local.
+///
+/// Returns a Result with the error being the HirId of the
+/// Upvar that was not found.
+fn to_upvars_resolved_place_builder<'a, 'tcx>(
+ from_builder: PlaceBuilder<'tcx>,
+ tcx: TyCtxt<'tcx>,
+ typeck_results: &'a ty::TypeckResults<'tcx>,
+) -> Result<PlaceBuilder<'tcx>, HirId> {
+ match from_builder.base {
+ PlaceBase::Local(_) => Ok(from_builder),
+ PlaceBase::Upvar { var_hir_id, closure_def_id, closure_kind } => {
+ // Captures are represented using fields inside a structure.
+ // This represents accessing self in the closure structure
+ let mut upvar_resolved_place_builder = PlaceBuilder::from(Local::new(1));
+ match closure_kind {
+ ty::ClosureKind::Fn | ty::ClosureKind::FnMut => {
+ upvar_resolved_place_builder = upvar_resolved_place_builder.deref();
+ }
+ ty::ClosureKind::FnOnce => {}
+ }
+
+ let (capture_index, capture_kind) =
+ if let Some(capture_details) = capture_matching_projections(
+ typeck_results,
+ var_hir_id,
+ closure_def_id,
+ &from_builder.projection,
+ ) {
+ capture_details
+ } else {
+ if !tcx.features().capture_disjoint_fields {
+ bug!(
+ "No associated capture found for {:?}[{:#?}] even though \
+ capture_disjoint_fields isn't enabled",
+ var_hir_id,
+ from_builder.projection
+ )
+ } else {
+ // FIXME(project-rfc-2229#24): Handle this case properly
+ debug!(
+ "No associated capture found for {:?}[{:#?}]",
+ var_hir_id,
+ from_builder.projection,
+ );
+ }
+ return Err(var_hir_id);
+ };
+
+ let closure_ty =
+ typeck_results.node_type(tcx.hir().local_def_id_to_hir_id(closure_def_id.expect_local()));
+
+ let substs = match closure_ty.kind() {
+ ty::Closure(_, substs) => ty::UpvarSubsts::Closure(substs),
+ ty::Generator(_, substs, _) => ty::UpvarSubsts::Generator(substs),
+ _ => bug!("Lowering capture for non-closure type {:?}", closure_ty),
+ };
+
+ // Access the capture by accessing the field within the Closure struct.
+ //
+ // We must have inferred the capture types since we are building MIR, therefore
+ // it's safe to call `upvar_tys` and we can unwrap here because
+ // we know that the capture exists and is the `capture_index`-th capture.
+ let var_ty = substs.upvar_tys().nth(capture_index).unwrap();
+
+ upvar_resolved_place_builder = upvar_resolved_place_builder.field(Field::new(capture_index), var_ty);
+
+ // If the variable is captured via ByRef(Immutable/Mutable) Borrow,
+ // we need to deref it
+ upvar_resolved_place_builder = match capture_kind {
+ ty::UpvarCapture::ByRef(_) => upvar_resolved_place_builder.deref(),
+ ty::UpvarCapture::ByValue(_) => upvar_resolved_place_builder,
+ };
+
+ let next_projection = 0;
+ let mut curr_projections = from_builder.projection;
+ upvar_resolved_place_builder.projection.extend(
+ curr_projections.drain(next_projection..));
+
+ Ok(upvar_resolved_place_builder)
+ }
+ }
+}
+
impl<'tcx> PlaceBuilder<'tcx> {
- fn into_place(self, tcx: TyCtxt<'tcx>) -> Place<'tcx> {
- Place { local: self.local, projection: tcx.intern_place_elems(&self.projection) }
+ fn into_place<'a>(
+ self,
+ tcx: TyCtxt<'tcx>,
+ typeck_results: &'a ty::TypeckResults<'tcx>,
+ ) -> Place<'tcx> {
+ if let PlaceBase::Local(local) = self.base {
+ Place { local, projection: tcx.intern_place_elems(&self.projection) }
+ } else {
+ self.expect_upvars_resolved(tcx, typeck_results).into_place(tcx, typeck_results)
+ }
+ }
+
+ fn expect_upvars_resolved<'a>(
+ self,
+ tcx: TyCtxt<'tcx>,
+ typeck_results: &'a ty::TypeckResults<'tcx>,
+ ) -> PlaceBuilder<'tcx> {
+ to_upvars_resolved_place_builder(self, tcx, typeck_results).unwrap()
}
fn field(self, f: Field, ty: Ty<'tcx>) -> Self {
impl<'tcx> From<Local> for PlaceBuilder<'tcx> {
fn from(local: Local) -> Self {
- Self { local, projection: Vec::new() }
+ Self { base: PlaceBase::Local(local), projection: Vec::new() }
+ }
+}
+
+impl<'tcx> From<PlaceBase> for PlaceBuilder<'tcx> {
+ fn from(base: PlaceBase) -> Self {
+ Self { base, projection: Vec::new() }
}
}
M: Mirror<'tcx, Output = Expr<'tcx>>,
{
let place_builder = unpack!(block = self.as_place_builder(block, expr));
- block.and(place_builder.into_place(self.hir.tcx()))
+ block.and(place_builder.into_place(self.hir.tcx(), self.hir.typeck_results()))
}
/// This is used when constructing a compound `Place`, so that we can avoid creating
M: Mirror<'tcx, Output = Expr<'tcx>>,
{
let place_builder = unpack!(block = self.as_read_only_place_builder(block, expr));
- block.and(place_builder.into_place(self.hir.tcx()))
+ block.and(place_builder.into_place(self.hir.tcx(), self.hir.typeck_results()))
}
/// This is used when constructing a compound `Place`, so that we can avoid creating
source_info,
),
ExprKind::UpvarRef { closure_def_id, var_hir_id } => {
- let capture = this
- .hir
- .typeck_results
- .closure_captures
- .get(&closure_def_id)
- .and_then(|captures| captures.get_full(&var_hir_id));
-
- if capture.is_none() {
- if !this.hir.tcx().features().capture_disjoint_fields {
- bug!(
- "No associated capture found for {:?} even though \
- capture_disjoint_fields isn't enabled",
- expr.kind
- )
- }
- // FIXME(project-rfc-2229#24): Handle this case properly
- }
-
- // Unwrap until the FIXME has been resolved
- let (capture_index, _, upvar_id) = capture.unwrap();
- this.lower_closure_capture(block, capture_index, *upvar_id)
+ let upvar_id = ty::UpvarId::new(var_hir_id, closure_def_id.expect_local());
+ this.lower_captured_upvar(block, upvar_id)
}
ExprKind::VarRef { id } => {
inferred_ty: expr.ty,
});
- let place = place_builder.clone().into_place(this.hir.tcx());
+ let place =
+ place_builder.clone().into_place(this.hir.tcx(), this.hir.typeck_results());
this.cfg.push(
block,
Statement {
}
}
- /// Lower a closure/generator capture by representing it as a field
- /// access within the desugared closure/generator.
- ///
- /// `capture_index` is the index of the capture within the desugared
- /// closure/generator.
- fn lower_closure_capture(
+ /// Lower a captured upvar. Note we might not know the actual capture index,
+ /// so we create a place starting from `PlaceBase::Upvar`, which will be resolved
+ /// once all projections that allow us to indentify a capture have been applied.
+ fn lower_captured_upvar(
&mut self,
block: BasicBlock,
- capture_index: usize,
upvar_id: ty::UpvarId,
- )
-> BlockAnd<PlaceBuilder<'tcx>> {
+ ) -> BlockAnd<PlaceBuilder<'tcx>> {
let closure_ty = self
.hir
.typeck_results()
.node_type(self.hir.tcx().hir().local_def_id_to_hir_id(upvar_id.closure_expr_id));
- // Captures are represented using fields inside a structure.
- // This represents accessing self in the closure structure
- let mut place_builder = PlaceBuilder::from(Local::new(1));
-
- // In case of Fn/FnMut closures we must deref to access the fields
- // Generators are considered FnOnce, so we ignore this step for them.
- if let ty::Closure(_, closure_substs) = closure_ty.kind() {
- match self.hir.infcx().closure_kind(closure_substs).unwrap() {
- ty::ClosureKind::Fn | ty::ClosureKind::FnMut => {
- place_builder = place_builder.deref();
- }
- ty::ClosureKind::FnOnce => {}
- }
- }
-
- let substs = match closure_ty.kind() {
- ty::Closure(_, substs) => ty::UpvarSubsts::Closure(substs),
- ty::Generator(_, substs, _) => ty::UpvarSubsts::Generator(substs),
- _ => bug!("Lowering capture for non-closure type {:?}", closure_ty)
+ let closure_kind = if let ty::Closure(_, closure_substs) = closure_ty.kind() {
+ self.hir.infcx().closure_kind(closure_substs).unwrap()
+ } else {
+ // Generators are considered FnOnce.
+ ty::ClosureKind::FnOnce
};
- // Access the capture by accessing the field within the Closure struct.
- //
- // We must have inferred the capture types since we are building MIR, therefore
- // it's safe to call `upvar_tys` and we can unwrap here because
- // we know that the capture exists and is the `capture_index`-th capture.
- let var_ty = substs.upvar_tys().nth(capture_index).unwrap();
- place_builder = place_builder.field(Field::new(capture_index), var_ty);
-
- // If the variable is captured via ByRef(Immutable/Mutable) Borrow,
- // we need to deref it
- match self.hir.typeck_results.upvar_capture(upvar_id) {
- ty::UpvarCapture::ByRef(_) => {
- block.and(place_builder.deref())
- }
- ty::UpvarCapture::ByValue(_) => block.and(place_builder),
- }
+ block.and(PlaceBuilder::from(PlaceBase::Upvar {
+ var_hir_id: upvar_id.var_path.hir_id,
+ closure_def_id: upvar_id.closure_expr_id.to_def_id(),
+ closure_kind,
+ }))
}
/// Lower an index expression
let is_outermost_index = fake_borrow_temps.is_none();
let fake_borrow_temps = fake_borrow_temps.unwrap_or(base_fake_borrow_temps);
- let base_place =
+ let mut base_place =
unpack!(block = self.expr_as_place(block, lhs, mutability, Some(fake_borrow_temps),));
// Making this a *fresh* temporary means we do not have to worry about
block = self.bounds_check(
block,
- base_place.clone().into_place(self.hir.tcx()),
+ base_place.clone().into_place(self.hir.tcx(), self.hir.typeck_results()),
idx,
expr_span,
source_info,
if is_outermost_index {
self.read_fake_borrows(block, fake_borrow_temps, source_info)
} else {
+ base_place = base_place.expect_upvars_resolved(self.hir.tcx(), self.hir.typeck_results());
self.add_fake_borrows_of_base(
&base_place,
block,
source_info: SourceInfo,
) {
let tcx = self.hir.tcx();
- let place_ty =
- Place::ty_from(base_place.local, &base_place.projection, &self.local_decls, tcx);
+ let local = match base_place.base {
+ PlaceBase::Local(local) => local,
+ PlaceBase::Upvar { .. } => bug!("Expected PlacseBase::Local found Upvar")
+ };
+
+ let place_ty = Place::ty_from(local, &base_place.projection, &self.local_decls, tcx);
if let ty::Slice(_) = place_ty.ty.kind() {
// We need to create fake borrows to ensure that the bounds
// check that we just did stays valid. Since we can't assign to
match elem {
ProjectionElem::Deref => {
let fake_borrow_deref_ty = Place::ty_from(
- base_place.local,
+ local,
&base_place.projection[..idx],
&self.local_decls,
tcx,
Rvalue::Ref(
tcx.lifetimes.re_erased,
BorrowKind::Shallow,
- Place { local: base_place.local, projection },
+ Place { local, projection },
),
);
fake_borrow_temps.push(fake_borrow_temp);
}
ProjectionElem::Index(_) => {
let index_ty = Place::ty_from(
- base_place.local,
+ local,
&base_place.projection[..idx],
&self.local_decls,
tcx,
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