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ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow #87069

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Merged
merged 5 commits into from
Jul 16, 2021
Merged

ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow #87069

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10b536f
ExprUseVisitor: treat ByValue use of Copy types as ImmBorrow
arora-aman Jul 11, 2021
36f51c9
Add test for copy type in move closure
arora-aman Jul 14, 2021
6c3774e
ExprUseVisitor::Delegate consume only when moving
arora-aman Jul 14, 2021
c4ac836
PR feedback
arora-aman Jul 15, 2021
75291ee
Update compiler/rustc_typeck/src/expr_use_visitor.rs
nikomatsakis Jul 15, 2021
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5 changes: 2 additions & 3 deletions compiler/rustc_typeck/src/check/upvar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1535,10 +1535,9 @@ impl<'a, 'tcx> InferBorrowKind<'a, 'tcx> {
place_with_id, diag_expr_id, mode
);

// Copy type being used as ByValue are equivalent to ImmBorrow and don't require any
// escalation.
// Copy types in ByValue scenarios need should be treated as ImmBorrows
match mode {
euv::ConsumeMode::Copy => return,
euv::ConsumeMode::Copy => unreachable!(),
euv::ConsumeMode::Move => {}
};

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24 changes: 19 additions & 5 deletions compiler/rustc_typeck/src/expr_use_visitor.rs
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Expand Up @@ -144,7 +144,13 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
debug!("delegate_consume(place_with_id={:?})", place_with_id);

let mode = copy_or_move(&self.mc, place_with_id);
self.delegate.consume(place_with_id, diag_expr_id, mode);

match mode {
ConsumeMode::Move => self.delegate.consume(place_with_id, diag_expr_id, mode),
ConsumeMode::Copy => {
self.delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
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Hmm, I had expected to make this change within the upvar delegate, and not the ExprUseVisitor. It seems potentially useful to some clients to know that this was a "by-value copy" -- I think there is other code in clippy that uses this, for example.

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Otherwise we should just remove the ConsumeMode

}
}
}

fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
Expand Down Expand Up @@ -653,9 +659,18 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
delegate.borrow(place, discr_place.hir_id, bk);
}
ty::BindByValue(..) => {
let mode = copy_or_move(mc, &place);
debug!("walk_pat binding consuming pat");
delegate.consume(place, discr_place.hir_id, mode);
let mode = copy_or_move(mc, &place);
match mode {
ConsumeMode::Move => {
delegate.consume(place, discr_place.hir_id, mode)
}
ConsumeMode::Copy => delegate.borrow(
place,
discr_place.hir_id,
ty::BorrowKind::ImmBorrow,
),
}
}
}
}
Expand Down Expand Up @@ -773,8 +788,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {

match capture_info.capture_kind {
ty::UpvarCapture::ByValue(_) => {
let mode = copy_or_move(&self.mc, &place_with_id);
self.delegate.consume(&place_with_id, place_with_id.hir_id, mode);
self.delegate_consume(&place_with_id, place_with_id.hir_id);
}
ty::UpvarCapture::ByRef(upvar_borrow) => {
self.delegate.borrow(
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