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Rollup merge of #83521 - sexxi-goose:quick-diagnostic-fix, r=nikomatsakis

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2229: Fix diagnostic issue when using FakeReads in closures

This PR fixes a diagnostic issue caused by https://github.com/rust-lang/rust/pull/82536. A temporary work around was used in this merged PR which involved feature gating the addition of FakeReads introduced as a result of pattern matching in closures.

The fix involves adding an optional closure DefId to ForLet and ForMatchedPlace FakeReadCauses. This DefId will only be added if a closure pattern matches a Place starting with an Upvar.

r? ```@nikomatsakis```
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Dylan DPC 2021-04-04 19:20:01 +02:00 • committed by GitHub
commit a89eab9bca
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39 changed files with 132 additions and 91 deletions
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20
compiler/rustc_middle/src/mir/mod.rs
View file

@ -1482,7 +1482,7 @@ pub enum StatementKind<'tcx> {
///
/// Note that this also is emitted for regular `let` bindings to ensure that locals that are
/// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
FakeRead(FakeReadCause, Box<Place<'tcx>>),
FakeRead(Box<(FakeReadCause, Place<'tcx>)>),
/// Write the discriminant for a variant to the enum Place.
SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
@ -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
///
@ -1618,7 +1628,9 @@ impl Debug for Statement<'_> {
use self::StatementKind::*;
match self.kind {
Assign(box (ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
FakeRead(ref cause, ref place) => write!(fmt, "FakeRead({:?}, {:?})", cause, place),
FakeRead(box (ref cause, ref place)) => {
write!(fmt, "FakeRead({:?}, {:?})", cause, place)
}
Retag(ref kind, ref place) => write!(
fmt,
"Retag({}{:?})",

2
compiler/rustc_middle/src/mir/visit.rs
View file

@ -380,7 +380,7 @@ macro_rules! make_mir_visitor {
) => {
self.visit_assign(place, rvalue, location);
}
StatementKind::FakeRead(_, place) => {
StatementKind::FakeRead(box (_, place)) => {
self.visit_place(
place,
PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect),