Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/next_solver/infer/snapshot/undo_log.rs')
| -rw-r--r-- | crates/hir-ty/src/next_solver/infer/snapshot/undo_log.rs | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/crates/hir-ty/src/next_solver/infer/snapshot/undo_log.rs b/crates/hir-ty/src/next_solver/infer/snapshot/undo_log.rs new file mode 100644 index 0000000000..05a1013b3f --- /dev/null +++ b/crates/hir-ty/src/next_solver/infer/snapshot/undo_log.rs @@ -0,0 +1,204 @@ +//! Snapshotting in the infer ctxt of the next-trait-solver. + +use std::marker::PhantomData; + +use ena::snapshot_vec as sv; +use ena::undo_log::{Rollback, UndoLogs}; +use ena::unify as ut; +use rustc_type_ir::FloatVid; +use rustc_type_ir::IntVid; +use tracing::debug; + +use crate::next_solver::OpaqueTypeKey; +use crate::next_solver::infer::opaque_types::OpaqueHiddenType; +use crate::next_solver::infer::unify_key::ConstVidKey; +use crate::next_solver::infer::unify_key::RegionVidKey; +use crate::next_solver::infer::{InferCtxtInner, region_constraints, type_variable}; +use crate::traits; + +pub struct Snapshot { + pub(crate) undo_len: usize, +} + +/// Records the "undo" data for a single operation that affects some form of inference variable. +#[derive(Clone)] +pub(crate) enum UndoLog<'db> { + DuplicateOpaqueType, + OpaqueTypes(OpaqueTypeKey<'db>, Option<OpaqueHiddenType<'db>>), + TypeVariables(type_variable::UndoLog<'db>), + ConstUnificationTable(sv::UndoLog<ut::Delegate<ConstVidKey<'db>>>), + IntUnificationTable(sv::UndoLog<ut::Delegate<IntVid>>), + FloatUnificationTable(sv::UndoLog<ut::Delegate<FloatVid>>), + RegionConstraintCollector(region_constraints::UndoLog<'db>), + RegionUnificationTable(sv::UndoLog<ut::Delegate<RegionVidKey<'db>>>), + PushRegionObligation, +} + +macro_rules! impl_from { + ($($ctor:ident ($ty:ty),)*) => { + $( + impl<'db> From<$ty> for UndoLog<'db> { + fn from(x: $ty) -> Self { + UndoLog::$ctor(x.into()) + } + } + )* + } +} + +// Upcast from a single kind of "undoable action" to the general enum +impl_from! { + RegionConstraintCollector(region_constraints::UndoLog<'db>), + + TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'db>>>), + TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidSubKey>>), + TypeVariables(type_variable::UndoLog<'db>), + IntUnificationTable(sv::UndoLog<ut::Delegate<IntVid>>), + FloatUnificationTable(sv::UndoLog<ut::Delegate<FloatVid>>), + + ConstUnificationTable(sv::UndoLog<ut::Delegate<ConstVidKey<'db>>>), + + RegionUnificationTable(sv::UndoLog<ut::Delegate<RegionVidKey<'db>>>), +} + +/// The Rollback trait defines how to rollback a particular action. +impl<'db> Rollback<UndoLog<'db>> for InferCtxtInner<'db> { + fn reverse(&mut self, undo: UndoLog<'db>) { + match undo { + UndoLog::DuplicateOpaqueType => self.opaque_type_storage.pop_duplicate_entry(), + UndoLog::OpaqueTypes(key, idx) => self.opaque_type_storage.remove(key, idx), + UndoLog::TypeVariables(undo) => self.type_variable_storage.reverse(undo), + UndoLog::ConstUnificationTable(undo) => self.const_unification_storage.reverse(undo), + UndoLog::IntUnificationTable(undo) => self.int_unification_storage.reverse(undo), + UndoLog::FloatUnificationTable(undo) => self.float_unification_storage.reverse(undo), + UndoLog::RegionConstraintCollector(undo) => { + self.region_constraint_storage.as_mut().unwrap().reverse(undo) + } + UndoLog::RegionUnificationTable(undo) => { + self.region_constraint_storage.as_mut().unwrap().unification_table.reverse(undo) + } + UndoLog::PushRegionObligation => { + self.region_obligations.pop(); + } + } + } +} + +/// The combined undo log for all the various unification tables. For each change to the storage +/// for any kind of inference variable, we record an UndoLog entry in the vector here. +#[derive(Clone, Default)] +pub(crate) struct InferCtxtUndoLogs<'db> { + logs: Vec<UndoLog<'db>>, + num_open_snapshots: usize, +} + +/// The UndoLogs trait defines how we undo a particular kind of action (of type T). We can undo any +/// action that is convertible into an UndoLog (per the From impls above). +impl<'db, T> UndoLogs<T> for InferCtxtUndoLogs<'db> +where + UndoLog<'db>: From<T>, +{ + #[inline] + fn num_open_snapshots(&self) -> usize { + self.num_open_snapshots + } + + #[inline] + fn push(&mut self, undo: T) { + if self.in_snapshot() { + self.logs.push(undo.into()) + } + } + + fn clear(&mut self) { + self.logs.clear(); + self.num_open_snapshots = 0; + } + + fn extend<J>(&mut self, undos: J) + where + Self: Sized, + J: IntoIterator<Item = T>, + { + if self.in_snapshot() { + self.logs.extend(undos.into_iter().map(UndoLog::from)) + } + } +} + +impl<'db> InferCtxtInner<'db> { + pub fn rollback_to(&mut self, snapshot: Snapshot) { + debug!("rollback_to({})", snapshot.undo_len); + self.undo_log.assert_open_snapshot(&snapshot); + + while self.undo_log.logs.len() > snapshot.undo_len { + let undo = self.undo_log.logs.pop().unwrap(); + self.reverse(undo); + } + + self.type_variable_storage.finalize_rollback(); + + if self.undo_log.num_open_snapshots == 1 { + // After the root snapshot the undo log should be empty. + assert!(snapshot.undo_len == 0); + assert!(self.undo_log.logs.is_empty()); + } + + self.undo_log.num_open_snapshots -= 1; + } + + pub fn commit(&mut self, snapshot: Snapshot) { + debug!("commit({})", snapshot.undo_len); + + if self.undo_log.num_open_snapshots == 1 { + // The root snapshot. It's safe to clear the undo log because + // there's no snapshot further out that we might need to roll back + // to. + assert!(snapshot.undo_len == 0); + self.undo_log.logs.clear(); + } + + self.undo_log.num_open_snapshots -= 1; + } +} + +impl<'db> InferCtxtUndoLogs<'db> { + pub(crate) fn start_snapshot(&mut self) -> Snapshot { + self.num_open_snapshots += 1; + Snapshot { undo_len: self.logs.len() } + } + + pub(crate) fn region_constraints_in_snapshot( + &self, + s: &Snapshot, + ) -> impl Iterator<Item = &'_ region_constraints::UndoLog<'db>> + Clone { + self.logs[s.undo_len..].iter().filter_map(|log| match log { + UndoLog::RegionConstraintCollector(log) => Some(log), + _ => None, + }) + } + + pub(crate) fn opaque_types_in_snapshot(&self, s: &Snapshot) -> bool { + self.logs[s.undo_len..].iter().any(|log| matches!(log, UndoLog::OpaqueTypes(..))) + } + + fn assert_open_snapshot(&self, snapshot: &Snapshot) { + // Failures here may indicate a failure to follow a stack discipline. + assert!(self.logs.len() >= snapshot.undo_len); + assert!(self.num_open_snapshots > 0); + } +} + +impl<'db> std::ops::Index<usize> for InferCtxtUndoLogs<'db> { + type Output = UndoLog<'db>; + + fn index(&self, key: usize) -> &Self::Output { + &self.logs[key] + } +} + +impl<'db> std::ops::IndexMut<usize> for InferCtxtUndoLogs<'db> { + fn index_mut(&mut self, key: usize) -> &mut Self::Output { + &mut self.logs[key] + } +} |