Stop computing error info in move path builder.

cjgillot · cjgillot · commit 2a29b20178a0 · 2023-09-30T20:23:34.000Z
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2483,9 +2483,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         /* Check if the mpi is initialized as an argument */
         let mut is_argument = false;
         for arg in self.body.args_iter() {
-            let path = self.move_data.rev_lookup.find_local(arg);
-            if mpis.contains(&path) {
-                is_argument = true;
+            if let Some(path) = self.move_data.rev_lookup.find_local(arg) {
+                if mpis.contains(&path) {
+                    is_argument = true;
+                }
             }
         }
 
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
@@ -1410,7 +1410,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         // As such we have to search for the local that this
                         // capture comes from and mark it as being used as mut.
 
-                        let temp_mpi = self.move_data.rev_lookup.find_local(local);
+                        let Some(temp_mpi) = self.move_data.rev_lookup.find_local(local) else {
+                            bug!("temporary should be tracked");
+                        };
                         let init = if let [init_index] = *self.move_data.init_path_map[temp_mpi] {
                             &self.move_data.inits[init_index]
                         } else {
@@ -2213,7 +2215,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         local: Local,
         flow_state: &Flows<'cx, 'tcx>,
     ) -> Option<InitIndex> {
-        let mpi = self.move_data.rev_lookup.find_local(local);
+        let mpi = self.move_data.rev_lookup.find_local(local)?;
         let ii = &self.move_data.init_path_map[mpi];
         ii.into_iter().find(|&&index| flow_state.ever_inits.contains(index)).copied()
     }
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -284,7 +284,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
     fn compute_drop_live_points_for(&mut self, local: Local) {
         debug!("compute_drop_live_points_for(local={:?})", local);
 
-        let mpi = self.cx.move_data.rev_lookup.find_local(local);
+        let Some(mpi) = self.cx.move_data.rev_lookup.find_local(local) else { return };
         debug!("compute_drop_live_points_for: mpi = {:?}", mpi);
 
         // Find the drops where `local` is initialized.
diff --git a/compiler/rustc_mir_dataflow/src/impls/initialized.rs b/compiler/rustc_mir_dataflow/src/impls/initialized.rs
@@ -690,9 +690,13 @@ impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, 'tcx> {
         if let mir::StatementKind::StorageDead(local) = stmt.kind {
             // End inits for StorageDead, so that an immutable variable can
             // be reinitialized on the next iteration of the loop.
-            let move_path_index = rev_lookup.find_local(local);
-            debug!("clears the ever initialized status of {:?}", init_path_map[move_path_index]);
-            trans.kill_all(init_path_map[move_path_index].iter().copied());
+            if let Some(move_path_index) = rev_lookup.find_local(local) {
+                debug!(
+                    "clears the ever initialized status of {:?}",
+                    init_path_map[move_path_index]
+                );
+                trans.kill_all(init_path_map[move_path_index].iter().copied());
+            }
         }
     }
 
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
@@ -7,8 +7,7 @@ use smallvec::{smallvec, SmallVec};
 use std::mem;
 
 use super::abs_domain::Lift;
-use super::IllegalMoveOriginKind::*;
-use super::{Init, InitIndex, InitKind, InitLocation, LookupResult, MoveError};
+use super::{Init, InitIndex, InitKind, InitLocation, LookupResult};
 use super::{
     LocationMap, MoveData, MoveOut, MoveOutIndex, MovePath, MovePathIndex, MovePathLookup,
 };
@@ -39,15 +38,15 @@ impl<'a, 'tcx> MoveDataBuilder<'a, 'tcx> {
                         .iter_enumerated()
                         .map(|(i, l)| {
                             if l.is_deref_temp() {
-                                MovePathIndex::MAX
+                                None
                             } else {
-                                Self::new_move_path(
+                                Some(Self::new_move_path(
                                     &mut move_paths,
                                     &mut path_map,
                                     &mut init_path_map,
                                     None,
                                     Place::from(i),
-                                )
+                                ))
                             }
                         })
                         .collect(),
@@ -88,6 +87,12 @@ impl<'a, 'tcx> MoveDataBuilder<'a, 'tcx> {
     }
 }
 
+enum MovePathResult {
+    Path(MovePathIndex),
+    Union(MovePathIndex),
+    Error,
+}
+
 impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
     /// This creates a MovePath for a given place, returning an `MovePathError`
     /// if that place can't be moved from.
@@ -96,11 +101,13 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
     /// problematic for borrowck.
     ///
     /// Maybe we should have separate "borrowck" and "moveck" modes.
-    fn move_path_for(&mut self, place: Place<'tcx>) -> Result<MovePathIndex, MoveError<'tcx>> {
+    fn move_path_for(&mut self, place: Place<'tcx>) -> MovePathResult {
         let data = &mut self.builder.data;
 
         debug!("lookup({:?})", place);
-        let mut base = data.rev_lookup.find_local(place.local);
+        let Some(mut base) = data.rev_lookup.find_local(place.local) else {
+            return MovePathResult::Error;
+        };
 
         // The move path index of the first union that we find. Once this is
         // some we stop creating child move paths, since moves from unions
@@ -116,12 +123,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             match elem {
                 ProjectionElem::Deref => match place_ty.kind() {
                     ty::Ref(..) | ty::RawPtr(..) => {
-                        return Err(MoveError::cannot_move_out_of(
-                            self.loc,
-                            BorrowedContent {
-                                target_place: place_ref.project_deeper(&[elem], tcx),
-                            },
-                        ));
+                        return MovePathResult::Error;
                     }
                     ty::Adt(adt, _) => {
                         if !adt.is_box() {
@@ -157,10 +159,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                 ProjectionElem::Field(_, _) => match place_ty.kind() {
                     ty::Adt(adt, _) => {
                         if adt.has_dtor(tcx) {
-                            return Err(MoveError::cannot_move_out_of(
-                                self.loc,
-                                InteriorOfTypeWithDestructor { container_ty: place_ty },
-                            ));
+                            return MovePathResult::Error;
                         }
                         if adt.is_union() {
                             union_path.get_or_insert(base);
@@ -195,33 +194,15 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                 ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
                     match place_ty.kind() {
                         ty::Slice(_) => {
-                            return Err(MoveError::cannot_move_out_of(
-                                self.loc,
-                                InteriorOfSliceOrArray {
-                                    ty: place_ty,
-                                    is_index: matches!(elem, ProjectionElem::Index(..)),
-                                },
-                            ));
+                            return MovePathResult::Error;
                         }
                         ty::Array(_, _) => (),
                         _ => bug!("Unexpected type {:#?}", place_ty.is_array()),
                     }
                 }
                 ProjectionElem::Index(_) => match place_ty.kind() {
-                    ty::Array(..) => {
-                        return Err(MoveError::cannot_move_out_of(
-                            self.loc,
-                            InteriorOfSliceOrArray { ty: place_ty, is_index: true },
-                        ));
-                    }
-                    ty::Slice(_) => {
-                        return Err(MoveError::cannot_move_out_of(
-                            self.loc,
-                            InteriorOfSliceOrArray {
-                                ty: place_ty,
-                                is_index: matches!(elem, ProjectionElem::Index(..)),
-                            },
-                        ));
+                    ty::Array(..) | ty::Slice(_) => {
+                        return MovePathResult::Error;
                     }
                     _ => bug!("Unexpected type {place_ty:#?}"),
                 },
@@ -247,9 +228,9 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
 
         if let Some(base) = union_path {
             // Move out of union - always move the entire union.
-            Err(MoveError::UnionMove { path: base })
+            MovePathResult::Union(base)
         } else {
-            Ok(base)
+            MovePathResult::Path(base)
         }
     }
 
@@ -325,17 +306,17 @@ pub(super) fn gather_moves<'tcx>(
 impl<'a, 'tcx> MoveDataBuilder<'a, 'tcx> {
     fn gather_args(&mut self) {
         for arg in self.body.args_iter() {
-            let path = self.data.rev_lookup.find_local(arg);
-
-            let init = self.data.inits.push(Init {
-                path,
-                kind: InitKind::Deep,
-                location: InitLocation::Argument(arg),
-            });
+            if let Some(path) = self.data.rev_lookup.find_local(arg) {
+                let init = self.data.inits.push(Init {
+                    path,
+                    kind: InitKind::Deep,
+                    location: InitLocation::Argument(arg),
+                });
 
-            debug!("gather_args: adding init {:?} of {:?} for argument {:?}", init, path, arg);
+                debug!("gather_args: adding init {:?} of {:?} for argument {:?}", init, path, arg);
 
-            self.data.init_path_map[path].push(init);
+                self.data.init_path_map[path].push(init);
+            }
         }
     }
 
@@ -538,12 +519,12 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             let base_place =
                 Place { local: place.local, projection: self.builder.tcx.mk_place_elems(base) };
             let base_path = match self.move_path_for(base_place) {
-                Ok(path) => path,
-                Err(MoveError::UnionMove { path }) => {
+                MovePathResult::Path(path) => path,
+                MovePathResult::Union(path) => {
                     self.record_move(place, path);
                     return;
                 }
-                Err(MoveError::IllegalMove { .. }) => {
+                MovePathResult::Error => {
                     return;
                 }
             };
@@ -563,8 +544,10 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             }
         } else {
             match self.move_path_for(place) {
-                Ok(path) | Err(MoveError::UnionMove { path }) => self.record_move(place, path),
-                Err(MoveError::IllegalMove { .. }) => {}
+                MovePathResult::Path(path) | MovePathResult::Union(path) => {
+                    self.record_move(place, path)
+                }
+                MovePathResult::Error => {}
             };
         }
     }
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
@@ -2,7 +2,7 @@ use crate::un_derefer::UnDerefer;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::*;
-use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
+use rustc_middle::ty::{ParamEnv, TyCtxt};
 use rustc_span::Span;
 use smallvec::SmallVec;
 
@@ -290,7 +290,7 @@ impl Init {
 /// Tables mapping from a place to its MovePathIndex.
 #[derive(Debug)]
 pub struct MovePathLookup<'tcx> {
-    locals: IndexVec<Local, MovePathIndex>,
+    locals: IndexVec<Local, Option<MovePathIndex>>,
 
     /// projections are made from a base-place and a projection
     /// elem. The base-place will have a unique MovePathIndex; we use
@@ -317,7 +317,9 @@ impl<'tcx> MovePathLookup<'tcx> {
     // unknown place, but will rather return the nearest available
     // parent.
     pub fn find(&self, place: PlaceRef<'tcx>) -> LookupResult {
-        let mut result = self.find_local(place.local);
+        let Some(mut result) = self.find_local(place.local) else {
+            return LookupResult::Parent(None);
+        };
 
         for (_, elem) in self.un_derefer.iter_projections(place) {
             if let Some(&subpath) = self.projections.get(&(result, elem.lift())) {
@@ -331,54 +333,16 @@ impl<'tcx> MovePathLookup<'tcx> {
     }
 
     #[inline]
-    pub fn find_local(&self, local: Local) -> MovePathIndex {
+    pub fn find_local(&self, local: Local) -> Option<MovePathIndex> {
         self.locals[local]
     }
 
     /// An enumerated iterator of `local`s and their associated
     /// `MovePathIndex`es.
     pub fn iter_locals_enumerated(
         &self,
-    ) -> impl DoubleEndedIterator<Item = (Local, MovePathIndex)> + ExactSizeIterator + '_ {
-        self.locals.iter_enumerated().map(|(l, &idx)| (l, idx))
-    }
-}
-
-#[derive(Debug)]
-pub struct IllegalMoveOrigin<'tcx> {
-    pub location: Location,
-    pub kind: IllegalMoveOriginKind<'tcx>,
-}
-
-#[derive(Debug)]
-pub enum IllegalMoveOriginKind<'tcx> {
-    /// Illegal move due to attempt to move from behind a reference.
-    BorrowedContent {
-        /// The place the reference refers to: if erroneous code was trying to
-        /// move from `(*x).f` this will be `*x`.
-        target_place: Place<'tcx>,
-    },
-
-    /// Illegal move due to attempt to move from field of an ADT that
-    /// implements `Drop`. Rust maintains invariant that all `Drop`
-    /// ADT's remain fully-initialized so that user-defined destructor
-    /// can safely read from all of the ADT's fields.
-    InteriorOfTypeWithDestructor { container_ty: Ty<'tcx> },
-
-    /// Illegal move due to attempt to move out of a slice or array.
-    InteriorOfSliceOrArray { ty: Ty<'tcx>, is_index: bool },
-}
-
-#[derive(Debug)]
-pub enum MoveError<'tcx> {
-    IllegalMove { cannot_move_out_of: IllegalMoveOrigin<'tcx> },
-    UnionMove { path: MovePathIndex },
-}
-
-impl<'tcx> MoveError<'tcx> {
-    pub fn cannot_move_out_of(location: Location, kind: IllegalMoveOriginKind<'tcx>) -> Self {
-        let origin = IllegalMoveOrigin { location, kind };
-        MoveError::IllegalMove { cannot_move_out_of: origin }
+    ) -> impl DoubleEndedIterator<Item = (Local, MovePathIndex)> + '_ {
+        self.locals.iter_enumerated().filter_map(|(l, &idx)| Some((l, idx?)))
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -2483,9 +2483,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {`
`2483`	`2483`	`/* Check if the mpi is initialized as an argument */`
`2484`	`2484`	`let mut is_argument = false;`
`2485`	`2485`	`for arg in self.body.args_iter() {`
`2486`		`- let path = self.move_data.rev_lookup.find_local(arg);`
`2487`		`- if mpis.contains(&path) {`
`2488`		`- is_argument = true;`
	`2486`	`+ if let Some(path) = self.move_data.rev_lookup.find_local(arg) {`
	`2487`	`+ if mpis.contains(&path) {`
	`2488`	`+ is_argument = true;`
	`2489`	`+ }`
`2489`	`2490`	`}`
`2490`	`2491`	`}`
`2491`	`2492`