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Fix diagnostic issue when using FakeReads in closures

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This commit is contained in:
Roxane 2021-03-25 23:03:12 -04:00
parent 138fd56cf9
commit 2fb1fb7634
31 changed files with 119 additions and 80 deletions
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16
compiler/rustc_middle/src/mir/mod.rs
View file

@ -1452,7 +1452,7 @@ pub struct Statement<'tcx> {
// `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Statement<'_>, 32);
static_assert_size!(Statement<'_>, 40);
impl Statement<'_> {
/// Changes a statement to a nop. This is both faster than deleting instructions and avoids
@ -1575,7 +1575,12 @@ pub enum FakeReadCause {
/// `let x: !; match x {}` doesn't generate any read of x so we need to
/// generate a read of x to check that it is initialized and safe.
ForMatchedPlace,
///
/// If a closure pattern matches a Place starting with an Upvar, then we introduce a
/// FakeRead for that Place outside the closure, in such a case this option would be
/// Some(closure_def_id).
/// Otherwise, the value of the optional DefId will be None.
ForMatchedPlace(Option<DefId>),
/// A fake read of the RefWithinGuard version of a bind-by-value variable
/// in a match guard to ensure that it's value hasn't change by the time
@ -1594,7 +1599,12 @@ pub enum FakeReadCause {
/// but in some cases it can affect the borrow checker, as in #53695.
/// Therefore, we insert a "fake read" here to ensure that we get
/// appropriate errors.
ForLet,
///
/// If a closure pattern matches a Place starting with an Upvar, then we introduce a
/// FakeRead for that Place outside the closure, in such a case this option would be
/// Some(closure_def_id).
/// Otherwise, the value of the optional DefId will be None.
ForLet(Option<DefId>),
/// If we have an index expression like
///

2
compiler/rustc_mir/src/borrow_check/diagnostics/explain_borrow.rs
View file

@ -515,7 +515,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let block = &self.body.basic_blocks()[location.block];
let kind = if let Some(&Statement {
kind: StatementKind::FakeRead(FakeReadCause::ForLet, _),
kind: StatementKind::FakeRead(FakeReadCause::ForLet(_), _),
..
}) = block.statements.get(location.statement_index)
{

22
compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs
View file

@ -7,8 +7,8 @@ use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItemGroup;
use rustc_hir::GeneratorKind;
use rustc_middle::mir::{
AggregateKind, Constant, Field, Local, LocalInfo, LocalKind, Location, Operand, Place,
PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
};
use rustc_middle::ty::print::Print;
use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt};
@ -795,6 +795,24 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
}
// StatementKind::FakeRead only contains a def_id if they are introduced as a result
// of pattern matching within a closure.
if let StatementKind::FakeRead(cause, box ref place) = stmt.kind {
match cause {
FakeReadCause::ForMatchedPlace(Some(closure_def_id))
| FakeReadCause::ForLet(Some(closure_def_id)) => {
debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
let places = &[Operand::Move(*place)];
if let Some((args_span, generator_kind, var_span)) =
self.closure_span(closure_def_id, moved_place, places)
{
return ClosureUse { generator_kind, args_span, var_span };
}
}
_ => {}
}
}
let normal_ret =
if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
PatUse(stmt.source_info.span)

30
compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
View file

@ -179,24 +179,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// match x { _ => () } // fake read of `x`
// };
// ```
// FIXME(RFC2229): Remove feature gate once diagnostics are improved
if this.tcx.features().capture_disjoint_fields {
for (thir_place, cause, hir_id) in fake_reads.into_iter() {
let place_builder =
unpack!(block = this.as_place_builder(block, thir_place));
for (thir_place, cause, hir_id) in fake_reads.into_iter() {
let place_builder = unpack!(block = this.as_place_builder(block, thir_place));
if let Ok(place_builder_resolved) =
place_builder.try_upvars_resolved(this.tcx, this.typeck_results)
{
let mir_place =
place_builder_resolved.into_place(this.tcx, this.typeck_results);
this.cfg.push_fake_read(
block,
this.source_info(this.tcx.hir().span(*hir_id)),
*cause,
mir_place,
);
}
if let Ok(place_builder_resolved) =
place_builder.try_upvars_resolved(this.tcx, this.typeck_results)
{
let mir_place =
place_builder_resolved.into_place(this.tcx, this.typeck_results);
this.cfg.push_fake_read(
block,
this.source_info(this.tcx.hir().span(*hir_id)),
*cause,
mir_place,
);
}
}

6
compiler/rustc_mir_build/src/build/matches/mod.rs
View file

@ -139,7 +139,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// uninhabited value. If we get never patterns, those will check that
// the place is initialized, and so this read would only be used to
// check safety.
let cause_matched_place = FakeReadCause::ForMatchedPlace;
let cause_matched_place = FakeReadCause::ForMatchedPlace(None);
let source_info = self.source_info(scrutinee_span);
if let Ok(scrutinee_builder) =
@ -400,7 +400,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// Inject a fake read, see comments on `FakeReadCause::ForLet`.
let source_info = self.source_info(irrefutable_pat.span);
self.cfg.push_fake_read(block, source_info, FakeReadCause::ForLet, place);
self.cfg.push_fake_read(block, source_info, FakeReadCause::ForLet(None), place);
self.schedule_drop_for_binding(var, irrefutable_pat.span, OutsideGuard);
block.unit()
@ -435,7 +435,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// Inject a fake read, see comments on `FakeReadCause::ForLet`.
let pattern_source_info = self.source_info(irrefutable_pat.span);
let cause_let = FakeReadCause::ForLet;
let cause_let = FakeReadCause::ForLet(None);
self.cfg.push_fake_read(block, pattern_source_info, cause_let, place);
let ty_source_info = self.source_info(user_ty_span);

21
compiler/rustc_typeck/src/expr_use_visitor.rs
View file

@ -280,9 +280,14 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
if needs_to_be_read {
self.borrow_expr(&discr, ty::ImmBorrow);
} else {
let closure_def_id = match discr_place.place.base {
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
_ => None,
};
self.delegate.fake_read(
discr_place.place.clone(),
FakeReadCause::ForMatchedPlace,
FakeReadCause::ForMatchedPlace(closure_def_id),
discr_place.hir_id,
);
@ -578,9 +583,14 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
}
fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
let closure_def_id = match discr_place.place.base {
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
_ => None,
};
self.delegate.fake_read(
discr_place.place.clone(),
FakeReadCause::ForMatchedPlace,
FakeReadCause::ForMatchedPlace(closure_def_id),
discr_place.hir_id,
);
self.walk_pat(discr_place, &arm.pat);
@ -595,9 +605,14 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
/// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
/// let binding, and *not* a match arm or nested pat.)
fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
let closure_def_id = match discr_place.place.base {
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
_ => None,
};
self.delegate.fake_read(
discr_place.place.clone(),
FakeReadCause::ForLet,
FakeReadCause::ForLet(closure_def_id),
discr_place.hir_id,
);
self.walk_pat(discr_place, pat);