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2229: Update signature for truncate function #88267

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Aug 25, 2021
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2229: Update signature for truncate function #88267

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118 changes: 48 additions & 70 deletions compiler/rustc_typeck/src/check/upvar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -489,7 +489,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let mut root_var_min_capture_list =
typeck_results.closure_min_captures.remove(&closure_def_id).unwrap_or_default();

for (place, capture_info) in capture_information.into_iter() {
for (mut place, capture_info) in capture_information.into_iter() {
let var_hir_id = match place.base {
PlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
base => bug!("Expected upvar, found={:?}", base),
Expand Down Expand Up @@ -530,14 +530,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

// Truncate the descendant (already in min_captures) to be same as the ancestor to handle any
// possible change in capture mode.
let (_, descendant_capture_kind) = truncate_place_to_len(
possible_descendant.place,
possible_descendant.info.capture_kind,
truncate_place_to_len_and_update_capture_kind(
&mut possible_descendant.place,
&mut possible_descendant.info.capture_kind,
place.projections.len(),
);

possible_descendant.info.capture_kind = descendant_capture_kind;

updated_capture_info =
determine_capture_info(updated_capture_info, possible_descendant.info);

Expand All @@ -561,14 +559,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

// Truncate the descendant (current place) to be same as the ancestor to handle any
// possible change in capture mode.
let (_, descendant_capture_kind) = truncate_place_to_len(
place.clone(),
updated_capture_info.capture_kind,
truncate_place_to_len_and_update_capture_kind(
&mut place,
&mut updated_capture_info.capture_kind,
possible_ancestor.place.projections.len(),
);

updated_capture_info.capture_kind = descendant_capture_kind;

possible_ancestor.info = determine_capture_info(
possible_ancestor.info,
updated_capture_info,
Expand Down Expand Up @@ -1476,7 +1472,7 @@ fn restrict_repr_packed_field_ref_capture<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
place: &Place<'tcx>,
curr_borrow_kind: ty::UpvarCapture<'tcx>,
mut curr_borrow_kind: ty::UpvarCapture<'tcx>,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
let pos = place.projections.iter().enumerate().position(|(i, p)| {
let ty = place.ty_before_projection(i);
Expand Down Expand Up @@ -1508,13 +1504,13 @@ fn restrict_repr_packed_field_ref_capture<'tcx>(
}
});

let place = place.clone();
let mut place = place.clone();

if let Some(pos) = pos {
truncate_place_to_len(place, curr_borrow_kind, pos)
} else {
(place, curr_borrow_kind)
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_borrow_kind, pos);
}

(place, curr_borrow_kind)
}

/// Returns a Ty that applies the specified capture kind on the provided capture Ty
Expand Down Expand Up @@ -1841,31 +1837,28 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> {
/// them completely.
/// - No projections are applied on top of Union ADTs, since these require unsafe blocks.
fn restrict_precision_for_unsafe(
place: Place<'tcx>,
curr_mode: ty::UpvarCapture<'tcx>,
mut place: Place<'tcx>,
mut curr_mode: ty::UpvarCapture<'tcx>,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
if place.projections.is_empty() {
// Nothing to do here
return (place, curr_mode);
}

if place.base_ty.is_unsafe_ptr() {
return truncate_place_to_len(place, curr_mode, 0);
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, 0);
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we used to return here, but now we don't? maybe this function also wants to take &mut arguments?

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we just return once at the bottom. Otherwise each of these has a return (place, curr_mode)

}

if place.base_ty.is_union() {
return truncate_place_to_len(place, curr_mode, 0);
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, 0);
}

for (i, proj) in place.projections.iter().enumerate() {
if proj.ty.is_unsafe_ptr() {
// Don't apply any projections on top of an unsafe ptr.
return truncate_place_to_len(place, curr_mode, i + 1);
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, i + 1);
break;
}

if proj.ty.is_union() {
// Don't capture preicse fields of a union.
return truncate_place_to_len(place, curr_mode, i + 1);
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, i + 1);
break;
}
}

Expand All @@ -1880,7 +1873,7 @@ fn restrict_capture_precision<'tcx>(
place: Place<'tcx>,
curr_mode: ty::UpvarCapture<'tcx>,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
let (place, curr_mode) = restrict_precision_for_unsafe(place, curr_mode);
let (mut place, mut curr_mode) = restrict_precision_for_unsafe(place, curr_mode);
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as above, I suspect this could take &mut place arguments


if place.projections.is_empty() {
// Nothing to do here
Expand All @@ -1891,7 +1884,8 @@ fn restrict_capture_precision<'tcx>(
match proj.kind {
ProjectionKind::Index => {
// Arrays are completely captured, so we drop Index projections
return truncate_place_to_len(place, curr_mode, i);
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, i);
return (place, curr_mode);
}
ProjectionKind::Deref => {}
ProjectionKind::Field(..) => {} // ignore
Expand All @@ -1906,8 +1900,8 @@ fn restrict_capture_precision<'tcx>(
/// (or if closure attempts to move data that it doesn’t own).
/// Note: When taking ownership, only capture data found on the stack.
fn adjust_for_move_closure<'tcx>(
place: Place<'tcx>,
kind: ty::UpvarCapture<'tcx>,
mut place: Place<'tcx>,
mut kind: ty::UpvarCapture<'tcx>,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
let contains_deref_of_ref = place.deref_tys().any(|ty| ty.is_ref());
let first_deref = place.projections.iter().position(|proj| proj.kind == ProjectionKind::Deref);
Expand All @@ -1917,52 +1911,38 @@ fn adjust_for_move_closure<'tcx>(

// If there's any Deref and the data needs to be moved into the closure body,
// or it's a Deref of a Box, truncate the path to the first deref
_ if first_deref.is_some() => {
let place = match first_deref {
Some(idx) => {
let (place, _) = truncate_place_to_len(place, kind, idx);
place
}
None => place,
};
_ => {
if let Some(idx) = first_deref {
truncate_place_to_len_and_update_capture_kind(&mut place, &mut kind, idx);
}

// AMAN: I think we don't need the span inside the ByValue anymore
// we have more detailed span in CaptureInfo
(place, ty::UpvarCapture::ByValue(None))
}

_ => (place, ty::UpvarCapture::ByValue(None)),
}
}

/// Adjust closure capture just that if taking ownership of data, only move data
/// from enclosing stack frame.
fn adjust_for_non_move_closure<'tcx>(
place: Place<'tcx>,
mut place: Place<'tcx>,
mut kind: ty::UpvarCapture<'tcx>,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
let contains_deref =
place.projections.iter().position(|proj| proj.kind == ProjectionKind::Deref);

match kind {
ty::UpvarCapture::ByValue(..) if contains_deref.is_some() => {
let place = match contains_deref {
Some(idx) => {
let (place, new_kind) = truncate_place_to_len(place, kind, idx);

kind = new_kind;
place
}
// Because of the if guard on the match on `kind`, we should never get here.
None => unreachable!(),
};

(place, kind)
ty::UpvarCapture::ByValue(..) => {
if let Some(idx) = contains_deref {
truncate_place_to_len_and_update_capture_kind(&mut place, &mut kind, idx);
}
}

ty::UpvarCapture::ByValue(..) => (place, kind),
ty::UpvarCapture::ByRef(..) => (place, kind),
ty::UpvarCapture::ByRef(..) => {}
}

(place, kind)
}

fn construct_place_string(tcx: TyCtxt<'_>, place: &Place<'tcx>) -> String {
Expand Down Expand Up @@ -2157,15 +2137,13 @@ fn determine_capture_info(
///
/// Note: Capture kind changes from `MutBorrow` to `UniqueImmBorrow` if the truncated part of the `place`
/// contained `Deref` of `&mut`.
fn truncate_place_to_len(
mut place: Place<'tcx>,
curr_mode: ty::UpvarCapture<'tcx>,
fn truncate_place_to_len_and_update_capture_kind(
place: &mut Place<'tcx>,
curr_mode: &mut ty::UpvarCapture<'tcx>,
len: usize,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
) {
let is_mut_ref = |ty: Ty<'_>| matches!(ty.kind(), ty::Ref(.., hir::Mutability::Mut));

let mut capture_kind = curr_mode;

// If the truncated part of the place contains `Deref` of a `&mut` then convert MutBorrow ->
// UniqueImmBorrow
// Note that if the place contained Deref of a raw pointer it would've not been MutBorrow, so
Expand All @@ -2176,7 +2154,7 @@ fn truncate_place_to_len(
if place.projections[i].kind == ProjectionKind::Deref
&& is_mut_ref(place.ty_before_projection(i))
{
capture_kind = ty::UpvarCapture::ByRef(ty::UpvarBorrow {
*curr_mode = ty::UpvarCapture::ByRef(ty::UpvarBorrow {
kind: ty::BorrowKind::UniqueImmBorrow,
region,
});
Expand All @@ -2190,8 +2168,6 @@ fn truncate_place_to_len(
}

place.projections.truncate(len);

(place, capture_kind)
}

/// Determines the Ancestry relationship of Place A relative to Place B
Expand Down Expand Up @@ -2256,8 +2232,8 @@ fn determine_place_ancestry_relation(
/// }
/// ```
fn truncate_capture_for_optimization<'tcx>(
place: Place<'tcx>,
curr_mode: ty::UpvarCapture<'tcx>,
mut place: Place<'tcx>,
mut curr_mode: ty::UpvarCapture<'tcx>,
) -> (Place<'tcx>, ty::UpvarCapture<'tcx>) {
let is_shared_ref = |ty: Ty<'_>| matches!(ty.kind(), ty::Ref(.., hir::Mutability::Not));

Expand All @@ -2269,10 +2245,12 @@ fn truncate_capture_for_optimization<'tcx>(
match idx {
// If that pointer is a shared reference, then we don't need those fields.
Some(idx) if is_shared_ref(place.ty_before_projection(idx)) => {
truncate_place_to_len(place, curr_mode, idx + 1)
truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, idx + 1)
}
None | Some(_) => (place, curr_mode),
None | Some(_) => {}
}

(place, curr_mode)
}

/// Precise capture is enabled if the feature gate `capture_disjoint_fields` is enabled or if
Expand Down