Rollup merge of #122468 - beepster4096:borrowck_prefixes_cleanup, r=Nadrieril
Cleanup `MirBorrowckCtxt::prefixes` Some of the uses of this method aren't necessary anymore and `PrefixSet::Supporting` is not used anywhere. With `PrefixSet::Supporting` removed, this could technically be moved to an extension trait on `PlaceRef`. However, it would have to be moved back to `MirBorrowckCtxt` when the `Derefer` MIR pass is moved before borrowck so I didn't.
This commit is contained in:
Guillaume Gomez
GitHub
commit
5c0012b953
@ -39,7 +39,7 @@ use crate::diagnostics::conflict_errors::StorageDeadOrDrop::LocalStorageDead;
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use crate::diagnostics::{find_all_local_uses, CapturedMessageOpt};
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use crate::{
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borrow_set::BorrowData, diagnostics::Instance, prefixes::IsPrefixOf,
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InitializationRequiringAction, MirBorrowckCtxt, PrefixSet, WriteKind,
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InitializationRequiringAction, MirBorrowckCtxt, WriteKind,
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};
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use super::{
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@ -114,7 +114,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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self.buffer_error(err);
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} else {
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if let Some((reported_place, _)) = self.has_move_error(&move_out_indices) {
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if self.prefixes(*reported_place, PrefixSet::All).any(|p| p == used_place) {
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if used_place.is_prefix_of(*reported_place) {
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debug!(
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"report_use_of_moved_or_uninitialized place: error suppressed mois={:?}",
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move_out_indices
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@ -1995,21 +1995,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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kind: Option<WriteKind>,
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) {
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let drop_span = place_span.1;
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let root_place =
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self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap();
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let borrowed_local = borrow.borrowed_place.local;
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let borrow_spans = self.retrieve_borrow_spans(borrow);
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let borrow_span = borrow_spans.var_or_use_path_span();
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assert!(root_place.projection.is_empty());
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let proper_span = self.body.local_decls[root_place.local].source_info.span;
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let proper_span = self.body.local_decls[borrowed_local].source_info.span;
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let root_place_projection = self.infcx.tcx.mk_place_elems(root_place.projection);
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if self.access_place_error_reported.contains(&(
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Place { local: root_place.local, projection: root_place_projection },
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borrow_span,
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)) {
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if self.access_place_error_reported.contains(&(Place::from(borrowed_local), borrow_span)) {
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debug!(
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"suppressing access_place error when borrow doesn't live long enough for {:?}",
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borrow_span
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@ -2017,12 +2010,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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return;
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}
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self.access_place_error_reported.insert((
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Place { local: root_place.local, projection: root_place_projection },
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borrow_span,
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));
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self.access_place_error_reported.insert((Place::from(borrowed_local), borrow_span));
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let borrowed_local = borrow.borrowed_place.local;
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if self.body.local_decls[borrowed_local].is_ref_to_thread_local() {
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let err =
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self.report_thread_local_value_does_not_live_long_enough(drop_span, borrow_span);
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@ -2544,9 +2533,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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};
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(format!("{local_kind}`{place_desc}`"), format!("`{place_desc}` is borrowed here"))
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} else {
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let root_place =
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self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap();
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let local = root_place.local;
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let local = borrow.borrowed_place.local;
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match self.body.local_kind(local) {
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LocalKind::Arg => (
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"function parameter".to_string(),
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@ -1,7 +1,4 @@
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//! From the NLL RFC: "The deep [aka 'supporting'] prefixes for an
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//! place are formed by stripping away fields and derefs, except that
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//! we stop when we reach the deref of a shared reference. [...] "
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//!
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//! From the NLL RFC:
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//! "Shallow prefixes are found by stripping away fields, but stop at
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//! any dereference. So: writing a path like `a` is illegal if `a.b`
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//! is borrowed. But: writing `a` is legal if `*a` is borrowed,
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@ -9,9 +6,7 @@
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use super::MirBorrowckCtxt;
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use rustc_hir as hir;
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use rustc_middle::mir::{Body, PlaceRef, ProjectionElem};
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_middle::mir::{PlaceRef, ProjectionElem};
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pub trait IsPrefixOf<'tcx> {
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fn is_prefix_of(&self, other: PlaceRef<'tcx>) -> bool;
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@ -25,9 +20,7 @@ impl<'tcx> IsPrefixOf<'tcx> for PlaceRef<'tcx> {
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}
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}
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pub(super) struct Prefixes<'cx, 'tcx> {
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body: &'cx Body<'tcx>,
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tcx: TyCtxt<'tcx>,
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pub(super) struct Prefixes<'tcx> {
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kind: PrefixSet,
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next: Option<PlaceRef<'tcx>>,
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}
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@ -39,24 +32,18 @@ pub(super) enum PrefixSet {
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All,
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/// Stops at any dereference.
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Shallow,
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/// Stops at the deref of a shared reference.
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Supporting,
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}
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impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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/// Returns an iterator over the prefixes of `place`
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/// (inclusive) from longest to smallest, potentially
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/// terminating the iteration early based on `kind`.
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pub(super) fn prefixes(
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&self,
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place_ref: PlaceRef<'tcx>,
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kind: PrefixSet,
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) -> Prefixes<'cx, 'tcx> {
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Prefixes { next: Some(place_ref), kind, body: self.body, tcx: self.infcx.tcx }
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pub(super) fn prefixes(&self, place_ref: PlaceRef<'tcx>, kind: PrefixSet) -> Prefixes<'tcx> {
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Prefixes { next: Some(place_ref), kind }
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}
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}
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impl<'cx, 'tcx> Iterator for Prefixes<'cx, 'tcx> {
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impl<'tcx> Iterator for Prefixes<'tcx> {
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type Item = PlaceRef<'tcx>;
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fn next(&mut self) -> Option<Self::Item> {
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let mut cursor = self.next?;
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@ -91,57 +78,23 @@ impl<'cx, 'tcx> Iterator for Prefixes<'cx, 'tcx> {
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panic!("Subtype projection is not allowed before borrow check")
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}
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ProjectionElem::Deref => {
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// (handled below)
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match self.kind {
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PrefixSet::Shallow => {
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// Shallow prefixes are found by stripping away
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// fields, but stop at *any* dereference.
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// So we can just stop the traversal now.
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self.next = None;
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return Some(cursor);
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}
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PrefixSet::All => {
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// All prefixes: just blindly enqueue the base
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// of the projection.
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self.next = Some(cursor_base);
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return Some(cursor);
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}
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}
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}
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}
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assert_eq!(elem, ProjectionElem::Deref);
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match self.kind {
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PrefixSet::Shallow => {
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// Shallow prefixes are found by stripping away
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// fields, but stop at *any* dereference.
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// So we can just stop the traversal now.
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self.next = None;
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return Some(cursor);
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}
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PrefixSet::All => {
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// All prefixes: just blindly enqueue the base
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// of the projection.
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self.next = Some(cursor_base);
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return Some(cursor);
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}
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PrefixSet::Supporting => {
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// Fall through!
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}
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}
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assert_eq!(self.kind, PrefixSet::Supporting);
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// Supporting prefixes: strip away fields and
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// derefs, except we stop at the deref of a shared
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// reference.
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let ty = cursor_base.ty(self.body, self.tcx).ty;
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match ty.kind() {
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ty::RawPtr(_) | ty::Ref(_ /*rgn*/, _ /*ty*/, hir::Mutability::Not) => {
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// don't continue traversing over derefs of raw pointers or shared
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// borrows.
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self.next = None;
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return Some(cursor);
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}
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ty::Ref(_ /*rgn*/, _ /*ty*/, hir::Mutability::Mut) => {
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self.next = Some(cursor_base);
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return Some(cursor);
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}
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ty::Adt(..) if ty.is_box() => {
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self.next = Some(cursor_base);
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return Some(cursor);
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}
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_ => panic!("unknown type fed to Projection Deref."),
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}
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}
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}
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}
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