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//! See docs in build/expr/mod.rs
use crate::build::expr::category::Category;
use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
use crate::build::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
use rustc_hir::def_id::LocalDefId;
use rustc_middle::hir::place::Projection as HirProjection;
use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
use rustc_middle::middle::region;
use rustc_middle::mir::AssertKind::BoundsCheck;
use rustc_middle::mir::*;
use rustc_middle::thir::*;
use rustc_middle::ty::AdtDef;
use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty, Variance};
use rustc_span::Span;
use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
use std::assert_matches::assert_matches;
use std::iter;
/// The "outermost" place that holds this value.
#[derive(Copy, Clone, Debug, PartialEq)]
pub(crate) 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
///
/// ```ignore (illustrative)
/// * 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: LocalVarId,
/// DefId of the closure
closure_def_id: LocalDefId,
},
}
/// `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 `to_place` method.
///
/// This is used internally when building a place for an expression like `a.b.c`. The fields `b`
/// and `c` can be progressively pushed onto the place builder that is created when converting `a`.
#[derive(Clone, Debug, PartialEq)]
pub(in crate::build) struct PlaceBuilder<'tcx> {
base: PlaceBase,
projection: Vec<PlaceElem<'tcx>>,
}
/// Given a list of MIR projections, convert them to list of HIR ProjectionKind.
/// The projections are truncated to represent a path that might be captured by a
/// closure/generator. This implies the vector returned from this function doesn't contain
/// ProjectionElems `Downcast`, `ConstantIndex`, `Index`, or `Subslice` because those will never be
/// part of a path that is captured by a closure. We stop applying projections once we see the first
/// projection that isn't captured by a closure.
fn convert_to_hir_projections_and_truncate_for_capture(
mir_projections: &[PlaceElem<'_>],
) -> Vec<HirProjectionKind> {
let mut hir_projections = Vec::new();
let mut variant = None;
for mir_projection in mir_projections {
let hir_projection = match mir_projection {
ProjectionElem::Deref => HirProjectionKind::Deref,
ProjectionElem::Field(field, _) => {
let variant = variant.unwrap_or(FIRST_VARIANT);
HirProjectionKind::Field(*field, variant)
}
ProjectionElem::Downcast(.., idx) => {
// We don't expect to see multi-variant enums here, as earlier
// phases will have truncated them already. However, there can
// still be downcasts, thanks to single-variant enums.
// We keep track of VariantIdx so we can use this information
// if the next ProjectionElem is a Field.
variant = Some(*idx);
continue;
}
// These do not affect anything, they just make sure we know the right type.
ProjectionElem::OpaqueCast(_) | ProjectionElem::Subtype(..) => continue,
ProjectionElem::Index(..)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. } => {
// We don't capture array-access projections.
// We can stop here as arrays are captured completely.
break;
}
};
variant = None;
hir_projections.push(hir_projection);
}
hir_projections
}
/// Return true if the `proj_possible_ancestor` represents an ancestor path
/// to `proj_capture` or `proj_possible_ancestor` is same as `proj_capture`,
/// assuming they both start off of the same root variable.
///
/// **Note:** It's the caller's responsibility to ensure that both lists of projections
/// start off of the same root variable.
///
/// Eg: 1. `foo.x` which is represented using `projections=[Field(x)]` is an ancestor of
/// `foo.x.y` which is represented using `projections=[Field(x), Field(y)]`.
/// Note both `foo.x` and `foo.x.y` start off of the same root variable `foo`.
/// 2. Since we only look at the projections here function will return `bar.x` as an a valid
/// ancestor of `foo.x.y`. It's the caller's responsibility to ensure that both projections
/// list are being applied to the same root variable.
fn is_ancestor_or_same_capture(
proj_possible_ancestor: &[HirProjectionKind],
proj_capture: &[HirProjectionKind],
) -> bool {
// We want to make sure `is_ancestor_or_same_capture("x.0.0", "x.0")` to return false.
// Therefore we can't just check if all projections are same in the zipped iterator below.
if proj_possible_ancestor.len() > proj_capture.len() {
return false;
}
iter::zip(proj_possible_ancestor, proj_capture).all(|(a, b)| a == b)
}
/// Given a closure, returns the index of a capture within the desugared closure struct and the
/// `ty::CapturedPlace` which is the ancestor of the Place represented using the `var_hir_id`
/// and `projection`.
///
/// Note there will be at most one ancestor for any given Place.
///
/// Returns None, when the ancestor is not found.
fn find_capture_matching_projections<'a, 'tcx>(
upvars: &'a CaptureMap<'tcx>,
var_hir_id: LocalVarId,
projections: &[PlaceElem<'tcx>],
) -> Option<(usize, &'a Capture<'tcx>)> {
let hir_projections = convert_to_hir_projections_and_truncate_for_capture(projections);
upvars.get_by_key_enumerated(var_hir_id.0).find(|(_, capture)| {
let possible_ancestor_proj_kinds: Vec<_> =
capture.captured_place.place.projections.iter().map(|proj| proj.kind).collect();
is_ancestor_or_same_capture(&possible_ancestor_proj_kinds, &hir_projections)
})
}
/// Takes an upvar place and tries to resolve it into a `PlaceBuilder`
/// with `PlaceBase::Local`
#[instrument(level = "trace", skip(cx), ret)]
fn to_upvars_resolved_place_builder<'tcx>(
cx: &Builder<'_, 'tcx>,
var_hir_id: LocalVarId,
closure_def_id: LocalDefId,
projection: &[PlaceElem<'tcx>],
) -> Option<PlaceBuilder<'tcx>> {
let Some((capture_index, capture)) =
find_capture_matching_projections(&cx.upvars, var_hir_id, &projection)
else {
let closure_span = cx.tcx.def_span(closure_def_id);
if !enable_precise_capture(closure_span) {
bug!(
"No associated capture found for {:?}[{:#?}] even though \
capture_disjoint_fields isn't enabled",
var_hir_id,
projection
)
} else {
debug!("No associated capture found for {:?}[{:#?}]", var_hir_id, projection,);
}
return None;
};
// Access the capture by accessing the field within the Closure struct.
let capture_info = &cx.upvars[capture_index];
let mut upvar_resolved_place_builder = PlaceBuilder::from(capture_info.use_place);
// We used some of the projections to build the capture itself,
// now we apply the remaining to the upvar resolved place.
trace!(?capture.captured_place, ?projection);
let remaining_projections = strip_prefix(
capture.captured_place.place.base_ty,
projection,
&capture.captured_place.place.projections,
);
upvar_resolved_place_builder.projection.extend(remaining_projections);
Some(upvar_resolved_place_builder)
}
/// Returns projections remaining after stripping an initial prefix of HIR
/// projections.
///
/// Supports only HIR projection kinds that represent a path that might be
/// captured by a closure or a generator, i.e., an `Index` or a `Subslice`
/// projection kinds are unsupported.
fn strip_prefix<'a, 'tcx>(
mut base_ty: Ty<'tcx>,
projections: &'a [PlaceElem<'tcx>],
prefix_projections: &[HirProjection<'tcx>],
) -> impl Iterator<Item = PlaceElem<'tcx>> + 'a {
let mut iter = projections
.iter()
.copied()
// Filter out opaque casts, they are unnecessary in the prefix.
.filter(|elem| !matches!(elem, ProjectionElem::OpaqueCast(..)));
for projection in prefix_projections {
match projection.kind {
HirProjectionKind::Deref => {
assert_matches!(iter.next(), Some(ProjectionElem::Deref));
}
HirProjectionKind::Field(..) => {
if base_ty.is_enum() {
assert_matches!(iter.next(), Some(ProjectionElem::Downcast(..)));
}
assert_matches!(iter.next(), Some(ProjectionElem::Field(..)));
}
HirProjectionKind::OpaqueCast => {
assert_matches!(iter.next(), Some(ProjectionElem::OpaqueCast(..)));
}
HirProjectionKind::Index | HirProjectionKind::Subslice => {
bug!("unexpected projection kind: {:?}", projection);
}
}
base_ty = projection.ty;
}
iter
}
impl<'tcx> PlaceBuilder<'tcx> {
pub(in crate::build) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
self.try_to_place(cx).unwrap()
}
/// Creates a `Place` or returns `None` if an upvar cannot be resolved
pub(in crate::build) fn try_to_place(&self, cx: &Builder<'_, 'tcx>) -> Option<Place<'tcx>> {
let resolved = self.resolve_upvar(cx);
let builder = resolved.as_ref().unwrap_or(self);
let PlaceBase::Local(local) = builder.base else { return None };
let projection = cx.tcx.mk_place_elems(&builder.projection);
Some(Place { local, projection })
}
/// Attempts to resolve the `PlaceBuilder`.
/// Returns `None` if this is not an upvar.
///
/// Upvars resolve may fail for a `PlaceBuilder` when attempting to
/// resolve a disjoint field whose root variable is not captured
/// (destructured assignments) or when attempting to resolve a root
/// variable (discriminant matching with only wildcard arm) that is
/// not captured. This can happen because the final mir that will be
/// generated doesn't require a read for this place. Failures will only
/// happen inside closures.
pub(in crate::build) fn resolve_upvar(
&self,
cx: &Builder<'_, 'tcx>,
) -> Option<PlaceBuilder<'tcx>> {
let PlaceBase::Upvar { var_hir_id, closure_def_id } = self.base else {
return None;
};
to_upvars_resolved_place_builder(cx, var_hir_id, closure_def_id, &self.projection)
}
pub(crate) fn base(&self) -> PlaceBase {
self.base
}
pub(crate) fn projection(&self) -> &[PlaceElem<'tcx>] {
&self.projection
}
pub(crate) fn field(self, f: FieldIdx, ty: Ty<'tcx>) -> Self {
self.project(PlaceElem::Field(f, ty))
}
pub(crate) fn deref(self) -> Self {
self.project(PlaceElem::Deref)
}
pub(crate) fn downcast(self, adt_def: AdtDef<'tcx>, variant_index: VariantIdx) -> Self {
self.project(PlaceElem::Downcast(Some(adt_def.variant(variant_index).name), variant_index))
}
fn index(self, index: Local) -> Self {
self.project(PlaceElem::Index(index))
}
pub(crate) fn project(mut self, elem: PlaceElem<'tcx>) -> Self {
self.projection.push(elem);
self
}
/// Same as `.clone().project(..)` but more efficient
pub(crate) fn clone_project(&self, elem: PlaceElem<'tcx>) -> Self {
Self {
base: self.base,
projection: Vec::from_iter(self.projection.iter().copied().chain([elem])),
}
}
}
impl<'tcx> From<Local> for PlaceBuilder<'tcx> {
fn from(local: Local) -> Self {
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() }
}
}
impl<'tcx> From<Place<'tcx>> for PlaceBuilder<'tcx> {
fn from(p: Place<'tcx>) -> Self {
Self { base: PlaceBase::Local(p.local), projection: p.projection.to_vec() }
}
}
impl<'a, 'tcx> Builder<'a, 'tcx> {
/// Compile `expr`, yielding a place that we can move from etc.
///
/// WARNING: Any user code might:
/// * Invalidate any slice bounds checks performed.
/// * Change the address that this `Place` refers to.
/// * Modify the memory that this place refers to.
/// * Invalidate the memory that this place refers to, this will be caught
/// by borrow checking.
///
/// Extra care is needed if any user code is allowed to run between calling
/// this method and using it, as is the case for `match` and index
/// expressions.
pub(crate) fn as_place(
&mut self,
mut block: BasicBlock,
expr: &Expr<'tcx>,
) -> BlockAnd<Place<'tcx>> {
let place_builder = unpack!(block = self.as_place_builder(block, expr));
block.and(place_builder.to_place(self))
}
/// This is used when constructing a compound `Place`, so that we can avoid creating
/// intermediate `Place` values until we know the full set of projections.
pub(crate) fn as_place_builder(
&mut self,
block: BasicBlock,
expr: &Expr<'tcx>,
) -> BlockAnd<PlaceBuilder<'tcx>> {
self.expr_as_place(block, expr, Mutability::Mut, None)
}
/// Compile `expr`, yielding a place that we can move from etc.
/// Mutability note: The caller of this method promises only to read from the resulting
/// place. The place itself may or may not be mutable:
/// * If this expr is a place expr like a.b, then we will return that place.
/// * Otherwise, a temporary is created: in that event, it will be an immutable temporary.
pub(crate) fn as_read_only_place(
&mut self,
mut block: BasicBlock,
expr: &Expr<'tcx>,
) -> BlockAnd<Place<'tcx>> {
let place_builder = unpack!(block = self.as_read_only_place_builder(block, expr));
block.and(place_builder.to_place(self))
}
/// This is used when constructing a compound `Place`, so that we can avoid creating
/// intermediate `Place` values until we know the full set of projections.
/// Mutability note: The caller of this method promises only to read from the resulting
/// place. The place itself may or may not be mutable:
/// * If this expr is a place expr like a.b, then we will return that place.
/// * Otherwise, a temporary is created: in that event, it will be an immutable temporary.
fn as_read_only_place_builder(
&mut self,
block: BasicBlock,
expr: &Expr<'tcx>,
) -> BlockAnd<PlaceBuilder<'tcx>> {
self.expr_as_place(block, expr, Mutability::Not, None)
}
fn expr_as_place(
&mut self,
mut block: BasicBlock,
expr: &Expr<'tcx>,
mutability: Mutability,
fake_borrow_temps: Option<&mut Vec<Local>>,
) -> BlockAnd<PlaceBuilder<'tcx>> {
debug!("expr_as_place(block={:?}, expr={:?}, mutability={:?})", block, expr, mutability);
let this = self;
let expr_span = expr.span;
let source_info = this.source_info(expr_span);
match expr.kind {
ExprKind::Scope { region_scope, lint_level, value } => {
this.in_scope((region_scope, source_info), lint_level, |this| {
this.expr_as_place(block, &this.thir[value], mutability, fake_borrow_temps)
})
}
ExprKind::Field { lhs, variant_index, name } => {
let lhs = &this.thir[lhs];
let mut place_builder =
unpack!(block = this.expr_as_place(block, lhs, mutability, fake_borrow_temps,));
if let ty::Adt(adt_def, _) = lhs.ty.kind() {
if adt_def.is_enum() {
place_builder = place_builder.downcast(*adt_def, variant_index);
}
}
block.and(place_builder.field(name, expr.ty))
}
ExprKind::Deref { arg } => {
let place_builder = unpack!(
block =
this.expr_as_place(block, &this.thir[arg], mutability, fake_borrow_temps,)
);
block.and(place_builder.deref())
}
ExprKind::Index { lhs, index } => this.lower_index_expression(
block,
&this.thir[lhs],
&this.thir[index],
mutability,
fake_borrow_temps,
expr.temp_lifetime,
expr_span,
source_info,
),
ExprKind::UpvarRef { closure_def_id, var_hir_id } => {
this.lower_captured_upvar(block, closure_def_id.expect_local(), var_hir_id)
}
ExprKind::VarRef { id } => {
let place_builder = if this.is_bound_var_in_guard(id) {
let index = this.var_local_id(id, RefWithinGuard);
PlaceBuilder::from(index).deref()
} else {
let index = this.var_local_id(id, OutsideGuard);
PlaceBuilder::from(index)
};
block.and(place_builder)
}
ExprKind::PlaceTypeAscription { source, ref user_ty } => {
let place_builder = unpack!(
block = this.expr_as_place(
block,
&this.thir[source],
mutability,
fake_borrow_temps,
)
);
if let Some(user_ty) = user_ty {
let annotation_index =
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span: source_info.span,
user_ty: user_ty.clone(),
inferred_ty: expr.ty,
});
let place = place_builder.to_place(this);
this.cfg.push(
block,
Statement {
source_info,
kind: StatementKind::AscribeUserType(
Box::new((
place,
UserTypeProjection { base: annotation_index, projs: vec![] },
)),
Variance::Invariant,
),
},
);
}
block.and(place_builder)
}
ExprKind::ValueTypeAscription { source, ref user_ty } => {
let source = &this.thir[source];
let temp =
unpack!(block = this.as_temp(block, source.temp_lifetime, source, mutability));
if let Some(user_ty) = user_ty {
let annotation_index =
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span: source_info.span,
user_ty: user_ty.clone(),
inferred_ty: expr.ty,
});
this.cfg.push(
block,
Statement {
source_info,
kind: StatementKind::AscribeUserType(
Box::new((
Place::from(temp),
UserTypeProjection { base: annotation_index, projs: vec![] },
)),
Variance::Invariant,
),
},
);
}
block.and(PlaceBuilder::from(temp))
}
ExprKind::Array { .. }
| ExprKind::Tuple { .. }
| ExprKind::Adt { .. }
| ExprKind::Closure { .. }
| ExprKind::Unary { .. }
| ExprKind::Binary { .. }
| ExprKind::LogicalOp { .. }
| ExprKind::Box { .. }
| ExprKind::Cast { .. }
| ExprKind::Use { .. }
| ExprKind::NeverToAny { .. }
| ExprKind::PointerCoercion { .. }
| ExprKind::Repeat { .. }
| ExprKind::Borrow { .. }
| ExprKind::AddressOf { .. }
| ExprKind::Match { .. }
| ExprKind::If { .. }
| ExprKind::Loop { .. }
| ExprKind::Block { .. }
| ExprKind::Let { .. }
| ExprKind::Assign { .. }
| ExprKind::AssignOp { .. }
| ExprKind::Break { .. }
| ExprKind::Continue { .. }
| ExprKind::Return { .. }
| ExprKind::Become { .. }
| ExprKind::Literal { .. }
| ExprKind::NamedConst { .. }
| ExprKind::NonHirLiteral { .. }
| ExprKind::ZstLiteral { .. }
| ExprKind::ConstParam { .. }
| ExprKind::ConstBlock { .. }
| ExprKind::StaticRef { .. }
| ExprKind::InlineAsm { .. }
| ExprKind::OffsetOf { .. }
| ExprKind::Yield { .. }
| ExprKind::ThreadLocalRef(_)
| ExprKind::Call { .. } => {
// these are not places, so we need to make a temporary.
debug_assert!(!matches!(Category::of(&expr.kind), Some(Category::Place)));
let temp =
unpack!(block = this.as_temp(block, expr.temp_lifetime, expr, mutability));
block.and(PlaceBuilder::from(temp))
}
}
}
/// 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 identify a capture have been applied.
fn lower_captured_upvar(
&mut self,
block: BasicBlock,
closure_def_id: LocalDefId,
var_hir_id: LocalVarId,
) -> BlockAnd<PlaceBuilder<'tcx>> {
block.and(PlaceBuilder::from(PlaceBase::Upvar { var_hir_id, closure_def_id }))
}
/// Lower an index expression
///
/// This has two complications;
///
/// * We need to do a bounds check.
/// * We need to ensure that the bounds check can't be invalidated using an
/// expression like `x[1][{x = y; 2}]`. We use fake borrows here to ensure
/// that this is the case.
fn lower_index_expression(
&mut self,
mut block: BasicBlock,
base: &Expr<'tcx>,
index: &Expr<'tcx>,
mutability: Mutability,
fake_borrow_temps: Option<&mut Vec<Local>>,
temp_lifetime: Option<region::Scope>,
expr_span: Span,
source_info: SourceInfo,
) -> BlockAnd<PlaceBuilder<'tcx>> {
let base_fake_borrow_temps = &mut Vec::new();
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 =
unpack!(block = self.expr_as_place(block, base, mutability, Some(fake_borrow_temps),));
// Making this a *fresh* temporary means we do not have to worry about
// the index changing later: Nothing will ever change this temporary.
// The "retagging" transformation (for Stacked Borrows) relies on this.
let idx = unpack!(block = self.as_temp(block, temp_lifetime, index, Mutability::Not,));
block = self.bounds_check(block, &base_place, idx, expr_span, source_info);
if is_outermost_index {
self.read_fake_borrows(block, fake_borrow_temps, source_info)
} else {
self.add_fake_borrows_of_base(
base_place.to_place(self),
block,
fake_borrow_temps,
expr_span,
source_info,
);
}
block.and(base_place.index(idx))
}
fn bounds_check(
&mut self,
block: BasicBlock,
slice: &PlaceBuilder<'tcx>,
index: Local,
expr_span: Span,
source_info: SourceInfo,
) -> BasicBlock {
let usize_ty = self.tcx.types.usize;
let bool_ty = self.tcx.types.bool;
// bounds check:
let len = self.temp(usize_ty, expr_span);
let lt = self.temp(bool_ty, expr_span);
// len = len(slice)
self.cfg.push_assign(block, source_info, len, Rvalue::Len(slice.to_place(self)));
// lt = idx < len
self.cfg.push_assign(
block,
source_info,
lt,
Rvalue::BinaryOp(
BinOp::Lt,
Box::new((Operand::Copy(Place::from(index)), Operand::Copy(len))),
),
);
let msg = BoundsCheck { len: Operand::Move(len), index: Operand::Copy(Place::from(index)) };
// assert!(lt, "...")
self.assert(block, Operand::Move(lt), true, msg, expr_span)
}
fn add_fake_borrows_of_base(
&mut self,
base_place: Place<'tcx>,
block: BasicBlock,
fake_borrow_temps: &mut Vec<Local>,
expr_span: Span,
source_info: SourceInfo,
) {
let tcx = self.tcx;
let place_ty = base_place.ty(&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
// unsized values, we only need to ensure that none of the
// pointers in the base place are modified.
for (base_place, elem) in base_place.iter_projections().rev() {
match elem {
ProjectionElem::Deref => {
let fake_borrow_deref_ty = base_place.ty(&self.local_decls, tcx).ty;
let fake_borrow_ty =
Ty::new_imm_ref(tcx, tcx.lifetimes.re_erased, fake_borrow_deref_ty);
let fake_borrow_temp =
self.local_decls.push(LocalDecl::new(fake_borrow_ty, expr_span));
let projection = tcx.mk_place_elems(&base_place.projection);
self.cfg.push_assign(
block,
source_info,
fake_borrow_temp.into(),
Rvalue::Ref(
tcx.lifetimes.re_erased,
BorrowKind::Shallow,
Place { local: base_place.local, projection },
),
);
fake_borrow_temps.push(fake_borrow_temp);
}
ProjectionElem::Index(_) => {
let index_ty = base_place.ty(&self.local_decls, tcx);
match index_ty.ty.kind() {
// The previous index expression has already
// done any index expressions needed here.
ty::Slice(_) => break,
ty::Array(..) => (),
_ => bug!("unexpected index base"),
}
}
ProjectionElem::Field(..)
| ProjectionElem::Downcast(..)
| ProjectionElem::OpaqueCast(..)
| ProjectionElem::Subtype(..)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. } => (),
}
}
}
}
fn read_fake_borrows(
&mut self,
bb: BasicBlock,
fake_borrow_temps: &mut Vec<Local>,
source_info: SourceInfo,
) {
// All indexes have been evaluated now, read all of the
// fake borrows so that they are live across those index
// expressions.
for temp in fake_borrow_temps {
self.cfg.push_fake_read(bb, source_info, FakeReadCause::ForIndex, Place::from(*temp));
}
}
}
/// Precise capture is enabled if user is using Rust Edition 2021 or higher.
fn enable_precise_capture(closure_span: Span) -> bool {
closure_span.at_least_rust_2021()
}