Flatten InferredCaptureInformation

Min capture computation can already handle the same place appearing twice,
and previous commits made CaptureInfo construction very cheap, so just
delegate all work to min capture and let InferBorrowKind and
process_collected_capture_information handle everything linearly.

Author: nbdd0121

compiler/rustc_typeck/src/check/upvar.rs

@@ -33,7 +33,6 @@
 use super::FnCtxt;
 
 use crate::expr_use_visitor as euv;
-use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
@@ -72,7 +71,7 @@ enum PlaceAncestryRelation {
 /// Intermediate format to store a captured `Place` and associated `ty::CaptureInfo`
 /// during capture analysis. Information in this map feeds into the minimum capture
 /// analysis pass.
-type InferredCaptureInformation<'tcx> = FxIndexMap<Place<'tcx>, ty::CaptureInfo>;
+type InferredCaptureInformation<'tcx> = Vec<(Place<'tcx>, ty::CaptureInfo)>;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub fn closure_analyze(&self, body: &'tcx hir::Body<'tcx>) {
@@ -258,7 +257,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         capture_kind,
                     };
 
-                    capture_information.insert(place, fake_info);
+                    capture_information.push((place, fake_info));
                 }
             }
 
@@ -384,76 +383,68 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         capture_clause: hir::CaptureBy,
         capture_information: InferredCaptureInformation<'tcx>,
     ) -> (InferredCaptureInformation<'tcx>, ty::ClosureKind, Option<(Span, Place<'tcx>)>) {
-        let mut processed: InferredCaptureInformation<'tcx> = Default::default();
-
         let mut closure_kind = ty::ClosureKind::LATTICE_BOTTOM;
         let mut origin: Option<(Span, Place<'tcx>)> = None;
 
-        for (place, mut capture_info) in capture_information {
-            // Apply rules for safety before inferring closure kind
-            let (place, capture_kind) =
-                restrict_capture_precision(place, capture_info.capture_kind);
-            capture_info.capture_kind = capture_kind;
+        let processed = capture_information
+            .into_iter()
+            .map(|(place, mut capture_info)| {
+                // Apply rules for safety before inferring closure kind
+                let (place, capture_kind) =
+                    restrict_capture_precision(place, capture_info.capture_kind);
 
-            let (place, capture_kind) =
-                truncate_capture_for_optimization(place, capture_info.capture_kind);
-            capture_info.capture_kind = capture_kind;
+                let (place, capture_kind) = truncate_capture_for_optimization(place, capture_kind);
 
-            let usage_span = if let Some(usage_expr) = capture_info.path_expr_id {
-                self.tcx.hir().span(usage_expr)
-            } else {
-                unreachable!()
-            };
+                let usage_span = if let Some(usage_expr) = capture_info.path_expr_id {
+                    self.tcx.hir().span(usage_expr)
+                } else {
+                    unreachable!()
+                };
 
-            let updated = match capture_info.capture_kind {
-                ty::UpvarCapture::ByValue => match closure_kind {
-                    ty::ClosureKind::Fn | ty::ClosureKind::FnMut => {
-                        (ty::ClosureKind::FnOnce, Some((usage_span, place.clone())))
-                    }
-                    // If closure is already FnOnce, don't update
-                    ty::ClosureKind::FnOnce => (closure_kind, origin),
-                },
+                let updated = match capture_kind {
+                    ty::UpvarCapture::ByValue => match closure_kind {
+                        ty::ClosureKind::Fn | ty::ClosureKind::FnMut => {
+                            (ty::ClosureKind::FnOnce, Some((usage_span, place.clone())))
+                        }
+                        // If closure is already FnOnce, don't update
+                        ty::ClosureKind::FnOnce => (closure_kind, origin.take()),
+                    },
 
-                ty::UpvarCapture::ByRef(
-                    ty::BorrowKind::MutBorrow | ty::BorrowKind::UniqueImmBorrow,
-                ) => {
-                    match closure_kind {
-                        ty::ClosureKind::Fn => {
-                            (ty::ClosureKind::FnMut, Some((usage_span, place.clone())))
+                    ty::UpvarCapture::ByRef(
+                        ty::BorrowKind::MutBorrow | ty::BorrowKind::UniqueImmBorrow,
+                    ) => {
+                        match closure_kind {
+                            ty::ClosureKind::Fn => {
+                                (ty::ClosureKind::FnMut, Some((usage_span, place.clone())))
+                            }
+                            // Don't update the origin
+                            ty::ClosureKind::FnMut | ty::ClosureKind::FnOnce => {
+                                (closure_kind, origin.take())
+                            }
                         }
-                        // Don't update the origin
-                        ty::ClosureKind::FnMut | ty::ClosureKind::FnOnce => (closure_kind, origin),
                     }
-                }
-
-                _ => (closure_kind, origin),
-            };
 
-            closure_kind = updated.0;
-            origin = updated.1;
+                    _ => (closure_kind, origin.take()),
+                };
 
-            let (place, capture_kind) = match capture_clause {
-                hir::CaptureBy::Value => adjust_for_move_closure(place, capture_info.capture_kind),
-                hir::CaptureBy::Ref => {
-                    adjust_for_non_move_closure(place, capture_info.capture_kind)
-                }
-            };
+                closure_kind = updated.0;
+                origin = updated.1;
 
-            // This restriction needs to be applied after we have handled adjustments for `move`
-            // closures. We want to make sure any adjustment that might make us move the place into
-            // the closure gets handled.
-            let (place, capture_kind) =
-                restrict_precision_for_drop_types(self, place, capture_kind, usage_span);
+                let (place, capture_kind) = match capture_clause {
+                    hir::CaptureBy::Value => adjust_for_move_closure(place, capture_kind),
+                    hir::CaptureBy::Ref => adjust_for_non_move_closure(place, capture_kind),
+                };
 
-            capture_info.capture_kind = capture_kind;
+                // This restriction needs to be applied after we have handled adjustments for `move`
+                // closures. We want to make sure any adjustment that might make us move the place into
+                // the closure gets handled.
+                let (place, capture_kind) =
+                    restrict_precision_for_drop_types(self, place, capture_kind, usage_span);
 
-            let capture_info = if let Some(existing) = processed.get(&place) {
-                determine_capture_info(*existing, capture_info)
-            } else {
-                capture_info
-            };
-            processed.insert(place, capture_info);
-        }
+                capture_info.capture_kind = capture_kind;
+                (place, capture_info)
+            })
+            .collect();
 
         (processed, closure_kind, origin)
     }
@@ -609,8 +600,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if !descendant_found {
                 for possible_ancestor in min_cap_list.iter_mut() {
                     match determine_place_ancestry_relation(&place, &possible_ancestor.place) {
+                        PlaceAncestryRelation::SamePlace => {
+                            ancestor_found = true;
+                            possible_ancestor.info = determine_capture_info(
+                                possible_ancestor.info,
+                                updated_capture_info,
+                            );
+
+                            // Only one related place will be in the list.
+                            break;
+                        }
                         // current place is descendant of possible_ancestor
-                        PlaceAncestryRelation::Descendant | PlaceAncestryRelation::SamePlace => {
+                        PlaceAncestryRelation::Descendant => {
                             ancestor_found = true;
                             let backup_path_expr_id = possible_ancestor.info.path_expr_id;
 
@@ -630,7 +631,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             // we need to keep the ancestor's `path_expr_id`
                             possible_ancestor.info.path_expr_id = backup_path_expr_id;
 
-                            // Only one ancestor of the current place will be in the list.
+                            // Only one related place will be in the list.
                             break;
                         }
                         _ => {}
@@ -1532,7 +1533,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn log_capture_analysis_first_pass(
         &self,
         closure_def_id: rustc_hir::def_id::DefId,
-        capture_information: &FxIndexMap<Place<'tcx>, ty::CaptureInfo>,
+        capture_information: &InferredCaptureInformation<'tcx>,
         closure_span: Span,
     ) {
         if self.should_log_capture_analysis(closure_def_id) {
@@ -1759,20 +1760,6 @@ struct InferBorrowKind<'a, 'tcx> {
     fake_reads: Vec<(Place<'tcx>, FakeReadCause, hir::HirId)>,
 }
 
-impl<'a, 'tcx> InferBorrowKind<'a, 'tcx> {
-    fn adjust_capture_info(&mut self, place: Place<'tcx>, capture_info: ty::CaptureInfo) {
-        match self.capture_information.get_mut(&place) {
-            Some(curr_info) => {
-                *curr_info = determine_capture_info(*curr_info, capture_info);
-            }
-            None => {
-                debug!("Capturing new place {:?}, capture_info={:?}", place, capture_info);
-                self.capture_information.insert(place, capture_info);
-            }
-        }
-    }
-}
-
 impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> {
     fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId) {
         let PlaceBase::Upvar(_) = place.base else { return };
@@ -1797,14 +1784,14 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> {
         let PlaceBase::Upvar(upvar_id) = place_with_id.place.base else { return };
         assert_eq!(self.closure_def_id, upvar_id.closure_expr_id);
 
-        self.adjust_capture_info(
+        self.capture_information.push((
             place_with_id.place.clone(),
             ty::CaptureInfo {
                 capture_kind_expr_id: Some(diag_expr_id),
                 path_expr_id: Some(diag_expr_id),
                 capture_kind: ty::UpvarCapture::ByValue,
             },
-        );
+        ));
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -1835,14 +1822,14 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> {
             capture_kind = ty::UpvarCapture::ByRef(ty::BorrowKind::ImmBorrow);
         }
 
-        self.adjust_capture_info(
+        self.capture_information.push((
             place,
             ty::CaptureInfo {
                 capture_kind_expr_id: Some(diag_expr_id),
                 path_expr_id: Some(diag_expr_id),
                 capture_kind,
             },
-        );
+        ));
     }
 
     #[instrument(skip(self), level = "debug")]

src/test/ui/closures/2229_closure_analysis/arrays-completely-captured.rs

@@ -15,6 +15,7 @@ fn main() {
         //~^ NOTE: Capturing m[] -> MutBorrow
         //~| NOTE: Min Capture m[] -> MutBorrow
         m[1] += 40;
+        //~^ NOTE: Capturing m[] -> MutBorrow
     };
 
     c();

src/test/ui/closures/2229_closure_analysis/arrays-completely-captured.stderr

@@ -15,7 +15,7 @@ LL | |
 LL | |
 LL | |         m[0] += 10;
 ...  |
-LL | |         m[1] += 40;
+LL | |
 LL | |     };
    | |_____^
    |
@@ -24,6 +24,11 @@ note: Capturing m[] -> MutBorrow
    |
 LL |         m[0] += 10;
    |         ^
+note: Capturing m[] -> MutBorrow
+  --> $DIR/arrays-completely-captured.rs:17:9
+   |
+LL |         m[1] += 40;
+   |         ^
 
 error: Min Capture analysis includes:
   --> $DIR/arrays-completely-captured.rs:11:5
@@ -33,7 +38,7 @@ LL | |
 LL | |
 LL | |         m[0] += 10;
 ...  |
-LL | |         m[1] += 40;
+LL | |
 LL | |     };
    | |_____^
    |

src/test/ui/closures/2229_closure_analysis/destructure_patterns.rs

@@ -15,6 +15,8 @@ fn arrays() {
     //~| ERROR: Min Capture analysis includes:
         let [a, b, .., e] = arr;
         //~^ NOTE: Capturing arr[Index] -> ByValue
+        //~| NOTE: Capturing arr[Index] -> ByValue
+        //~| NOTE: Capturing arr[Index] -> ByValue
         //~| NOTE: Min Capture arr[] -> ByValue
         assert_eq!(a, "A");
         assert_eq!(b, "B");