1016 lines
40 KiB
Rust
1016 lines
40 KiB
Rust
//! See docs in build/expr/mod.rs
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use crate::build::expr::category::Category;
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use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
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use crate::build::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
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use rustc_hir::def_id::LocalDefId;
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use rustc_middle::hir::place::Projection as HirProjection;
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use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
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use rustc_middle::middle::region;
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use rustc_middle::mir::tcx::PlaceTy;
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use rustc_middle::mir::AssertKind::BoundsCheck;
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use rustc_middle::mir::*;
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use rustc_middle::thir::*;
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use rustc_middle::ty::AdtDef;
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use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty, TyCtxt, Variance};
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use rustc_span::Span;
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use rustc_target::abi::VariantIdx;
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use rustc_index::vec::Idx;
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use std::assert_matches::assert_matches;
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use std::convert::From;
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use std::iter;
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/// `PlaceBuilder` is used to create places during MIR construction. It allows you to "build up" a
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/// place by pushing more and more projections onto the end, and then convert the final set into a
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/// place using the `into_place` method.
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///
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/// This is used internally when building a place for an expression like `a.b.c`. The fields `b`
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/// and `c` can be progressively pushed onto the place builder that is created when converting `a`.
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#[derive(Clone, Debug, PartialEq)]
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pub(in crate::build) enum PlaceBuilder<'tcx> {
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/// Denotes the start of a `Place`.
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///
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/// We use `PlaceElem` since this has all `Field` types available.
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Local(Local, Vec<PlaceElem<'tcx>>),
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/// When building place for an expression within a closure, the place might start off a
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/// captured path. When `capture_disjoint_fields` is enabled, we might not know the capture
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/// index (within the desugared closure) of the captured path until most of the projections
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/// are applied. We use `PlaceBuilder::Upvar` to keep track of the root variable off of which the
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/// captured path starts, the closure the capture belongs to and the trait the closure
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/// implements.
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///
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/// Once we have figured out the capture index, we can convert the place builder to
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/// `PlaceBuilder::Local`.
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///
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/// Consider the following example
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/// ```rust
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/// let t = (((10, 10), 10), 10);
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///
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/// let c = || {
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/// println!("{}", t.0.0.0);
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/// };
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/// ```
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/// Here the THIR expression for `t.0.0.0` will be something like
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///
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/// ```ignore (illustrative)
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/// * Field(0)
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/// * Field(0)
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/// * Field(0)
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/// * UpvarRef(t)
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/// ```
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///
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/// When `capture_disjoint_fields` is enabled, `t.0.0.0` is captured and we won't be able to
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/// figure out that it is captured until all the `Field` projections are applied.
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///
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/// Note: in contrast to `PlaceBuilder::Local` we have not yet determined all `Field` types
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/// and will only do so once converting to `PlaceBuilder::Local`.
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UpVar(UpVar, Vec<UpvarProjectionElem<'tcx>>),
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}
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#[derive(Copy, Clone, Debug, PartialEq)]
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pub(crate) struct UpVar {
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var_hir_id: LocalVarId,
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closure_def_id: LocalDefId,
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}
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/// Given a list of MIR projections, convert them to list of HIR ProjectionKind.
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/// The projections are truncated to represent a path that might be captured by a
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/// closure/generator. This implies the vector returned from this function doesn't contain
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/// ProjectionElems `Downcast`, `ConstantIndex`, `Index`, or `Subslice` because those will never be
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/// part of a path that is captured by a closure. We stop applying projections once we see the first
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/// projection that isn't captured by a closure.
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fn convert_to_hir_projections_and_truncate_for_capture<'tcx>(
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mir_projections: &[UpvarProjectionElem<'tcx>],
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) -> Vec<HirProjectionKind> {
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let mut hir_projections = Vec::new();
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let mut variant = None;
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for mir_projection in mir_projections {
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let hir_projection = match mir_projection {
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ProjectionElem::Deref => HirProjectionKind::Deref,
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ProjectionElem::Field(field, _) => {
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let variant = variant.unwrap_or(VariantIdx::new(0));
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HirProjectionKind::Field(field.index() as u32, variant)
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}
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ProjectionElem::Downcast(.., idx) => {
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// We don't expect to see multi-variant enums here, as earlier
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// phases will have truncated them already. However, there can
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// still be downcasts, thanks to single-variant enums.
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// We keep track of VariantIdx so we can use this information
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// if the next ProjectionElem is a Field.
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variant = Some(*idx);
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continue;
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}
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// These do not affect anything, they just make sure we know the right type.
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ProjectionElem::OpaqueCast(_) => continue,
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ProjectionElem::Index(..)
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| ProjectionElem::ConstantIndex { .. }
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| ProjectionElem::Subslice { .. } => {
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// We don't capture array-access projections.
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// We can stop here as arrays are captured completely.
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break;
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}
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};
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variant = None;
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hir_projections.push(hir_projection);
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}
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hir_projections
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}
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/// Return true if the `proj_possible_ancestor` represents an ancestor path
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/// to `proj_capture` or `proj_possible_ancestor` is same as `proj_capture`,
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/// assuming they both start off of the same root variable.
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///
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/// **Note:** It's the caller's responsibility to ensure that both lists of projections
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/// start off of the same root variable.
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///
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/// Eg: 1. `foo.x` which is represented using `projections=[Field(x)]` is an ancestor of
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/// `foo.x.y` which is represented using `projections=[Field(x), Field(y)]`.
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/// Note both `foo.x` and `foo.x.y` start off of the same root variable `foo`.
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/// 2. Since we only look at the projections here function will return `bar.x` as an a valid
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/// ancestor of `foo.x.y`. It's the caller's responsibility to ensure that both projections
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/// list are being applied to the same root variable.
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fn is_ancestor_or_same_capture(
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proj_possible_ancestor: &[HirProjectionKind],
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proj_capture: &[HirProjectionKind],
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) -> bool {
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// We want to make sure `is_ancestor_or_same_capture("x.0.0", "x.0")` to return false.
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// Therefore we can't just check if all projections are same in the zipped iterator below.
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if proj_possible_ancestor.len() > proj_capture.len() {
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return false;
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}
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iter::zip(proj_possible_ancestor, proj_capture).all(|(a, b)| a == b)
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}
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/// Given a closure, returns the index of a capture within the desugared closure struct and the
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/// `ty::CapturedPlace` which is the ancestor of the Place represented using the `var_hir_id`
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/// and `projection`.
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///
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/// Note there will be at most one ancestor for any given Place.
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///
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/// Returns None, when the ancestor is not found.
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fn find_capture_matching_projections<'a, 'tcx>(
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upvars: &'a CaptureMap<'tcx>,
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var_hir_id: LocalVarId,
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projections: &[UpvarProjectionElem<'tcx>],
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) -> Option<(usize, &'a Capture<'tcx>)> {
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let hir_projections = convert_to_hir_projections_and_truncate_for_capture(projections);
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upvars.get_by_key_enumerated(var_hir_id.0).find(|(_, capture)| {
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let possible_ancestor_proj_kinds: Vec<_> =
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capture.captured_place.place.projections.iter().map(|proj| proj.kind).collect();
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is_ancestor_or_same_capture(&possible_ancestor_proj_kinds, &hir_projections)
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})
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}
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/// Takes an upvar place and tries to resolve it into a `PlaceBuilder`
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/// with `PlaceBase::Local`
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#[instrument(level = "trace", skip(cx), ret)]
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fn to_upvars_resolved_place_builder<'tcx>(
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cx: &Builder<'_, 'tcx>,
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var_hir_id: LocalVarId,
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closure_def_id: LocalDefId,
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projection: &[UpvarProjectionElem<'tcx>],
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) -> Option<PlaceBuilder<'tcx>> {
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let Some((capture_index, capture)) =
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find_capture_matching_projections(
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&cx.upvars,
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var_hir_id,
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&projection,
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) else {
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let closure_span = cx.tcx.def_span(closure_def_id);
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if !enable_precise_capture(cx.tcx, closure_span) {
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bug!(
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"No associated capture found for {:?}[{:#?}] even though \
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capture_disjoint_fields isn't enabled",
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var_hir_id,
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projection
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)
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} else {
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debug!(
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"No associated capture found for {:?}[{:#?}]",
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var_hir_id, projection,
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);
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}
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return None;
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};
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// Access the capture by accessing the field within the Closure struct.
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let capture_info = &cx.upvars[capture_index];
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let Place { local: upvar_resolved_local, projection: local_projection } =
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capture_info.use_place;
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// We used some of the projections to build the capture itself,
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// now we apply the remaining to the upvar resolved place.
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let upvar_projection = strip_prefix(
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capture.captured_place.place.base_ty,
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projection,
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&capture.captured_place.place.projections,
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);
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let upvar_resolved_place_builder = PlaceBuilder::construct_local_place_builder(
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cx,
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upvar_resolved_local,
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local_projection.as_slice(),
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upvar_projection,
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);
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debug_assert!({
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let builder = upvar_resolved_place_builder.clone();
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let mut valid_conversion = true;
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match builder {
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PlaceBuilder::Local(_, projections) => {
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for proj in projections.iter() {
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match proj {
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ProjectionElem::Field(_, field_ty) => {
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if matches!(field_ty.kind(), ty::Infer(..)) {
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debug!(
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"field ty should have been converted for projection {:?} in PlaceBuilder {:?}",
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proj,
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upvar_resolved_place_builder.clone()
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);
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valid_conversion = false;
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break;
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}
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}
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_ => {}
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}
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}
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}
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PlaceBuilder::UpVar(..) => {
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unreachable!()
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}
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}
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valid_conversion
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});
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Some(upvar_resolved_place_builder)
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}
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/// Returns projections remaining after stripping an initial prefix of HIR
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/// projections.
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///
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/// Supports only HIR projection kinds that represent a path that might be
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/// captured by a closure or a generator, i.e., an `Index` or a `Subslice`
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/// projection kinds are unsupported.
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fn strip_prefix<'a, 'tcx>(
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mut base_ty: Ty<'tcx>,
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projections: &'a [UpvarProjectionElem<'tcx>],
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prefix_projections: &[HirProjection<'tcx>],
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) -> impl Iterator<Item = UpvarProjectionElem<'tcx>> + 'a {
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let mut iter = projections
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.iter()
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// Filter out opaque casts, they are unnecessary in the prefix.
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.filter(|elem| !matches!(elem, ProjectionElem::OpaqueCast(..)))
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.map(|elem| *elem);
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for projection in prefix_projections {
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debug!(?projection, ?projection.ty);
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match projection.kind {
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HirProjectionKind::Deref => {
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assert_matches!(iter.next(), Some(ProjectionElem::Deref));
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}
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HirProjectionKind::Field(..) => {
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if base_ty.is_enum() {
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assert_matches!(iter.next(), Some(ProjectionElem::Downcast(..)));
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}
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assert_matches!(iter.next(), Some(ProjectionElem::Field(..)));
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}
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HirProjectionKind::Index | HirProjectionKind::Subslice => {
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bug!("unexpected projection kind: {:?}", projection);
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}
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}
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base_ty = projection.ty;
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}
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iter
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}
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impl<'tcx> PlaceBuilder<'tcx> {
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pub(in crate::build) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
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self.try_to_place(cx).unwrap()
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}
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/// Creates a `Place` or returns `None` if an upvar cannot be resolved
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pub(in crate::build) fn try_to_place(&self, cx: &Builder<'_, 'tcx>) -> Option<Place<'tcx>> {
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let resolved = self.resolve_upvar(cx);
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let builder = resolved.as_ref().unwrap_or(self);
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let PlaceBuilder::Local(local, projection) = builder else { return None };
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let projection = cx.tcx.intern_place_elems(&projection);
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Some(Place { local: *local, projection })
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}
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/// Attempts to resolve the `PlaceBuilder`.
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/// Returns `None` if this is not an upvar.
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///
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/// Upvars resolve may fail for a `PlaceBuilder` when attempting to
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/// resolve a disjoint field whose root variable is not captured
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/// (destructured assignments) or when attempting to resolve a root
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/// variable (discriminant matching with only wildcard arm) that is
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/// not captured. This can happen because the final mir that will be
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/// generated doesn't require a read for this place. Failures will only
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/// happen inside closures.
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pub(in crate::build) fn resolve_upvar(
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&self,
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cx: &Builder<'_, 'tcx>,
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) -> Option<PlaceBuilder<'tcx>> {
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let PlaceBuilder::UpVar( UpVar {var_hir_id, closure_def_id }, projection) = self else {
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return None;
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};
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to_upvars_resolved_place_builder(cx, *var_hir_id, *closure_def_id, &projection)
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}
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pub(crate) fn get_local_projection(&self) -> &[PlaceElem<'tcx>] {
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match self {
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Self::Local(_, projection) => projection,
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Self::UpVar(..) => {
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bug!("get_local_projection_mut can only be called on PlaceBuilder::Local")
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}
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}
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}
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#[instrument(skip(cx), level = "debug")]
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pub(crate) fn field(self, cx: &Builder<'_, 'tcx>, f: Field) -> Self {
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let field_ty = match self.clone() {
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PlaceBuilder::Local(local, projection) => {
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let base_place = PlaceBuilder::Local(local, projection);
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let PlaceTy { ty, variant_index } =
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base_place.to_place(cx).ty(&cx.local_decls, cx.tcx);
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let base_ty = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
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PlaceBuilder::compute_field_ty(cx, f, base_ty, variant_index)
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}
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PlaceBuilder::UpVar(..) => {
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let dummy_ty = cx.tcx.mk_ty_infer(ty::FreshTy(0));
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dummy_ty
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}
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};
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self.project(ProjectionElem::Field(f, field_ty))
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}
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pub(crate) fn deref(self) -> Self {
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self.project(PlaceElem::Deref)
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}
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pub(crate) fn downcast(self, adt_def: AdtDef<'tcx>, variant_index: VariantIdx) -> Self {
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self.project(PlaceElem::Downcast(Some(adt_def.variant(variant_index).name), variant_index))
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}
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fn index(self, index: Local) -> Self {
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self.project(PlaceElem::Index(index))
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}
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#[instrument(level = "debug")]
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pub(crate) fn project(self, elem: PlaceElem<'tcx>) -> Self {
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let result = match self {
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PlaceBuilder::Local(local, mut proj) => {
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proj.push(elem);
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PlaceBuilder::Local(local, proj)
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}
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PlaceBuilder::UpVar(upvar, mut proj) => {
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proj.push(elem.into());
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PlaceBuilder::UpVar(upvar, proj)
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}
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};
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debug!(?result);
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result
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}
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/// Same as `.clone().project(..)` but more efficient
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pub(crate) fn clone_project(&self, elem: PlaceElem<'tcx>) -> Self {
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match self {
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PlaceBuilder::Local(local, proj) => PlaceBuilder::Local(
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*local,
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Vec::from_iter(proj.iter().copied().chain([elem.into()])),
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),
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PlaceBuilder::UpVar(upvar, proj) => PlaceBuilder::UpVar(
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*upvar,
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Vec::from_iter(proj.iter().copied().chain([elem.into()])),
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),
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}
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}
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/// Similar to `Place::ty` but needed during mir building.
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///
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/// Applies the projections in the `PlaceBuilder` to the base
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/// type.
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///
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/// Fallible as the root of this place may be an upvar for
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/// which no base type can be determined.
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#[instrument(skip(cx), level = "debug")]
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fn compute_field_ty(
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cx: &Builder<'_, 'tcx>,
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field: Field,
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base_ty: Ty<'tcx>,
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variant_index: Option<VariantIdx>,
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) -> Ty<'tcx> {
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let field_idx = field.as_usize();
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let field_ty = match base_ty.kind() {
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ty::Adt(adt_def, substs) if adt_def.is_enum() => {
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let variant_idx = variant_index.unwrap();
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adt_def.variant(variant_idx).fields[field_idx].ty(cx.tcx, substs)
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}
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ty::Adt(adt_def, substs) => adt_def
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.all_fields()
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.nth(field_idx)
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.unwrap_or_else(|| {
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bug!(
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"expected to take field with idx {:?} of fields of {:?}",
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field_idx,
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adt_def
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)
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})
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.ty(cx.tcx, substs),
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ty::Tuple(elems) => elems.iter().nth(field_idx).unwrap_or_else(|| {
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bug!("expected to take field with idx {:?} of {:?}", field_idx, elems)
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}),
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ty::Closure(_, substs) => {
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let substs = substs.as_closure();
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let Some(f_ty) = substs.upvar_tys().nth(field_idx) else {
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bug!("expected to take field with idx {:?} of {:?}", field_idx, substs.upvar_tys().collect::<Vec<_>>());
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};
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f_ty
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}
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&ty::Generator(def_id, substs, _) => {
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if let Some(var) = variant_index {
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let gen_body = cx.tcx.optimized_mir(def_id);
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let Some(layout) = gen_body.generator_layout() else {
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bug!("No generator layout for {:?}", base_ty);
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};
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let Some(&local) = layout.variant_fields[var].get(field) else {
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bug!("expected to take field {:?} of {:?}", field, layout.variant_fields[var]);
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};
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let Some(&f_ty) = layout.field_tys.get(local) else {
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bug!("expected to get element for {:?} in {:?}", local, layout.field_tys);
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};
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f_ty
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} else {
|
|
let Some(f_ty) = substs.as_generator().prefix_tys().nth(field.index()) else {
|
|
bug!("expected to take index {:?} in {:?}", field.index(), substs.as_generator().prefix_tys().collect::<Vec<_>>());
|
|
};
|
|
|
|
f_ty
|
|
}
|
|
}
|
|
_ => bug!("couldn't create field type, unexpected base type: {:?}", base_ty),
|
|
};
|
|
|
|
cx.tcx.normalize_erasing_regions(cx.param_env, field_ty)
|
|
}
|
|
|
|
/// Creates a `PlaceBuilder::Local` from a `PlaceBuilder::UpVar` whose upvars
|
|
/// are resolved. This function takes two kinds of projections: `local_projection`
|
|
/// contains the projections of the captured upvar and `upvar_projection` the
|
|
/// projections that are applied to the captured upvar. The main purpose of this
|
|
/// function is to figure out the `Ty`s of the field projections in `upvar_projection`.
|
|
#[instrument(skip(cx, local, upvar_projection))]
|
|
fn construct_local_place_builder(
|
|
cx: &Builder<'_, 'tcx>,
|
|
local: Local,
|
|
local_projection: &[PlaceElem<'tcx>],
|
|
upvar_projection: impl Iterator<Item = UpvarProjectionElem<'tcx>>,
|
|
) -> Self {
|
|
// We maintain a `Ty` to which we apply a projection in each iteration over `upvar_projection`.
|
|
// This `ancestor_ty` let's us infer the field type whenever we encounter a
|
|
// `ProjectionElem::Field`.
|
|
let (mut ancestor_ty, mut opt_variant_idx) =
|
|
local_projections_to_ty(cx, local, local_projection);
|
|
|
|
// We add all projection elements we encounter to this `Vec`.
|
|
let mut local_projection = local_projection.to_vec();
|
|
|
|
for (i, proj) in upvar_projection.enumerate() {
|
|
debug!("i: {:?}, proj: {:?}, local_projection: {:?}", i, proj, local_projection);
|
|
match proj {
|
|
ProjectionElem::Field(field, _) => {
|
|
let field_ty =
|
|
PlaceBuilder::compute_field_ty(cx, field, ancestor_ty, opt_variant_idx);
|
|
debug!(?field_ty);
|
|
|
|
local_projection.push(ProjectionElem::Field(field, field_ty));
|
|
ancestor_ty = field_ty;
|
|
opt_variant_idx = None;
|
|
}
|
|
_ => {
|
|
let proj = upvar_proj_to_place_elem_no_field_proj(proj);
|
|
(ancestor_ty, opt_variant_idx) = project_ty(cx.tcx, ancestor_ty, proj);
|
|
local_projection.push(proj);
|
|
}
|
|
}
|
|
}
|
|
|
|
PlaceBuilder::Local(local, local_projection)
|
|
}
|
|
}
|
|
|
|
impl<'tcx> From<Local> for PlaceBuilder<'tcx> {
|
|
fn from(local: Local) -> Self {
|
|
Self::Local(local, Vec::new())
|
|
}
|
|
}
|
|
|
|
impl<'tcx> From<Place<'tcx>> for PlaceBuilder<'tcx> {
|
|
fn from(p: Place<'tcx>) -> Self {
|
|
Self::Local(p.local, p.projection.to_vec())
|
|
}
|
|
}
|
|
|
|
fn project_ty<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
ty: Ty<'tcx>,
|
|
elem: PlaceElem<'tcx>,
|
|
) -> (Ty<'tcx>, Option<VariantIdx>) {
|
|
match elem {
|
|
ProjectionElem::Deref => {
|
|
let updated_ty = ty
|
|
.builtin_deref(true)
|
|
.unwrap_or_else(|| bug!("deref projection of non-dereferenceable ty {:?}", ty))
|
|
.ty;
|
|
|
|
(updated_ty, None)
|
|
}
|
|
ProjectionElem::Index(_) | ProjectionElem::ConstantIndex { .. } => {
|
|
(ty.builtin_index().unwrap(), None)
|
|
}
|
|
ProjectionElem::Subslice { from, to, from_end } => {
|
|
let ty = match ty.kind() {
|
|
ty::Slice(..) => ty,
|
|
ty::Array(inner, _) if !from_end => tcx.mk_array(*inner, (to - from) as u64),
|
|
ty::Array(inner, size) if from_end => {
|
|
let size = size.eval_usize(tcx, ty::ParamEnv::empty());
|
|
let len = size - (from as u64) - (to as u64);
|
|
tcx.mk_array(*inner, len)
|
|
}
|
|
_ => bug!("cannot subslice non-array type: `{:?}`", ty),
|
|
};
|
|
|
|
(ty, None)
|
|
}
|
|
ProjectionElem::Downcast(_, variant_idx) => (ty, Some(variant_idx)),
|
|
ProjectionElem::Field(_, ty) => {
|
|
if matches!(ty.kind(), ty::Infer(..)) {
|
|
bug!("Field ty should have been resolved");
|
|
}
|
|
|
|
(ty, None)
|
|
}
|
|
ProjectionElem::OpaqueCast(..) => bug!("didn't expect OpaqueCast"),
|
|
}
|
|
}
|
|
|
|
fn local_projections_to_ty<'a, 'tcx>(
|
|
cx: &'a Builder<'a, 'tcx>,
|
|
local: Local,
|
|
projection: &'a [PlaceElem<'tcx>],
|
|
) -> (Ty<'tcx>, Option<VariantIdx>) {
|
|
let local_ty = cx.local_decls.local_decls()[local].ty;
|
|
projection.iter().fold((local_ty, None), |ty_variant_idx, elem| {
|
|
let ty = ty_variant_idx.0;
|
|
project_ty(cx.tcx, ty, *elem)
|
|
})
|
|
}
|
|
|
|
// Converts an `UpvarProjectionElem` to `PlaceElem`, ICE'ing when being passed a
|
|
// field projection.
|
|
fn upvar_proj_to_place_elem_no_field_proj<'tcx>(
|
|
upvar_proj: UpvarProjectionElem<'tcx>,
|
|
) -> PlaceElem<'tcx> {
|
|
match upvar_proj {
|
|
ProjectionElem::Deref => ProjectionElem::Deref,
|
|
ProjectionElem::Index(i) => ProjectionElem::Index(i),
|
|
ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
|
|
ProjectionElem::ConstantIndex { offset, min_length, from_end }
|
|
}
|
|
ProjectionElem::Subslice { from, to, from_end } => {
|
|
ProjectionElem::Subslice { from, to, from_end }
|
|
}
|
|
ProjectionElem::Downcast(ty, variant_idx) => ProjectionElem::Downcast(ty, variant_idx),
|
|
ProjectionElem::OpaqueCast(ty) => ProjectionElem::OpaqueCast(ty),
|
|
ProjectionElem::Field(..) => bug!("should not be called with `ProjectionElem::Field`"),
|
|
}
|
|
}
|
|
|
|
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)
|
|
}
|
|
|
|
#[instrument(skip(self, fake_borrow_temps), level = "debug")]
|
|
fn expr_as_place(
|
|
&mut self,
|
|
mut block: BasicBlock,
|
|
expr: &Expr<'tcx>,
|
|
mutability: Mutability,
|
|
fake_borrow_temps: Option<&mut Vec<Local>>,
|
|
) -> BlockAnd<PlaceBuilder<'tcx>> {
|
|
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,));
|
|
debug!(?place_builder);
|
|
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(this, name))
|
|
}
|
|
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::Pointer { .. }
|
|
| 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::Literal { .. }
|
|
| ExprKind::NamedConst { .. }
|
|
| ExprKind::NonHirLiteral { .. }
|
|
| ExprKind::ZstLiteral { .. }
|
|
| ExprKind::ConstParam { .. }
|
|
| ExprKind::ConstBlock { .. }
|
|
| ExprKind::StaticRef { .. }
|
|
| ExprKind::InlineAsm { .. }
|
|
| 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 `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::UpVar(UpVar { var_hir_id, closure_def_id }, vec![]))
|
|
}
|
|
|
|
/// 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 (idx, elem) in base_place.projection.iter().enumerate().rev() {
|
|
match elem {
|
|
ProjectionElem::Deref => {
|
|
let fake_borrow_deref_ty = Place::ty_from(
|
|
base_place.local,
|
|
&base_place.projection[..idx],
|
|
&self.local_decls,
|
|
tcx,
|
|
)
|
|
.ty;
|
|
let fake_borrow_ty =
|
|
tcx.mk_imm_ref(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.intern_place_elems(&base_place.projection[..idx]);
|
|
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 = Place::ty_from(
|
|
base_place.local,
|
|
&base_place.projection[..idx],
|
|
&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::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 the feature gate `capture_disjoint_fields` is enabled or if
|
|
/// user is using Rust Edition 2021 or higher.
|
|
fn enable_precise_capture(tcx: TyCtxt<'_>, closure_span: Span) -> bool {
|
|
tcx.features().capture_disjoint_fields || closure_span.rust_2021()
|
|
}
|