move snapshot handling into mod

compiler/rustc_infer/src/infer/mod.rs

@@ -7,12 +7,10 @@ pub use self::SubregionOrigin::*;
 pub use self::ValuePairs::*;
 pub use relate::combine::ObligationEmittingRelation;
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::undo_log::UndoLogs;
 use rustc_middle::infer::unify_key::EffectVarValue;
 use rustc_middle::infer::unify_key::{ConstVidKey, EffectVidKey};
 
 use self::opaque_types::OpaqueTypeStorage;
-pub(crate) use self::undo_log::{InferCtxtUndoLogs, Snapshot, UndoLog};
 
 use crate::traits::{
     self, ObligationCause, ObligationInspector, PredicateObligations, TraitEngine, TraitEngineExt,
@@ -50,11 +48,10 @@ use self::error_reporting::TypeErrCtxt;
 use self::free_regions::RegionRelations;
 use self::lexical_region_resolve::LexicalRegionResolutions;
 use self::region_constraints::{GenericKind, VarInfos, VerifyBound};
-use self::region_constraints::{
-    RegionConstraintCollector, RegionConstraintStorage, RegionSnapshot,
-};
+use self::region_constraints::{RegionConstraintCollector, RegionConstraintStorage};
 pub use self::relate::combine::CombineFields;
 pub use self::relate::StructurallyRelateAliases;
+use self::snapshot::undo_log::InferCtxtUndoLogs;
 use self::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 
 pub mod at;
@@ -62,7 +59,6 @@ pub mod canonical;
 pub mod error_reporting;
 pub mod free_regions;
 mod freshen;
-mod fudge;
 mod lexical_region_resolve;
 pub mod opaque_types;
 pub mod outlives;
@@ -70,8 +66,8 @@ mod projection;
 pub mod region_constraints;
 mod relate;
 pub mod resolve;
+pub(crate) mod snapshot;
 pub mod type_variable;
-mod undo_log;
 
 #[must_use]
 #[derive(Debug)]
@@ -738,13 +734,6 @@ impl<'tcx> InferOk<'tcx, ()> {
     }
 }
 
-#[must_use = "once you start a snapshot, you should always consume it"]
-pub struct CombinedSnapshot<'tcx> {
-    undo_snapshot: Snapshot<'tcx>,
-    region_constraints_snapshot: RegionSnapshot,
-    universe: ty::UniverseIndex,
-}
-
 impl<'tcx> InferCtxt<'tcx> {
     pub fn dcx(&self) -> &'tcx DiagCtxt {
         self.tcx.dcx()
@@ -842,90 +831,6 @@ impl<'tcx> InferCtxt<'tcx> {
         }
     }
 
-    pub fn in_snapshot(&self) -> bool {
-        UndoLogs::<UndoLog<'tcx>>::in_snapshot(&self.inner.borrow_mut().undo_log)
-    }
-
-    pub fn num_open_snapshots(&self) -> usize {
-        UndoLogs::<UndoLog<'tcx>>::num_open_snapshots(&self.inner.borrow_mut().undo_log)
-    }
-
-    fn start_snapshot(&self) -> CombinedSnapshot<'tcx> {
-        debug!("start_snapshot()");
-
-        let mut inner = self.inner.borrow_mut();
-
-        CombinedSnapshot {
-            undo_snapshot: inner.undo_log.start_snapshot(),
-            region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
-            universe: self.universe(),
-        }
-    }
-
-    #[instrument(skip(self, snapshot), level = "debug")]
-    fn rollback_to(&self, snapshot: CombinedSnapshot<'tcx>) {
-        let CombinedSnapshot { undo_snapshot, region_constraints_snapshot, universe } = snapshot;
-
-        self.universe.set(universe);
-
-        let mut inner = self.inner.borrow_mut();
-        inner.rollback_to(undo_snapshot);
-        inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot);
-    }
-
-    #[instrument(skip(self, snapshot), level = "debug")]
-    fn commit_from(&self, snapshot: CombinedSnapshot<'tcx>) {
-        let CombinedSnapshot { undo_snapshot, region_constraints_snapshot: _, universe: _ } =
-            snapshot;
-
-        self.inner.borrow_mut().commit(undo_snapshot);
-    }
-
-    /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
-    #[instrument(skip(self, f), level = "debug")]
-    pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
-    where
-        F: FnOnce(&CombinedSnapshot<'tcx>) -> Result<T, E>,
-    {
-        let snapshot = self.start_snapshot();
-        let r = f(&snapshot);
-        debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
-        match r {
-            Ok(_) => {
-                self.commit_from(snapshot);
-            }
-            Err(_) => {
-                self.rollback_to(snapshot);
-            }
-        }
-        r
-    }
-
-    /// Execute `f` then unroll any bindings it creates.
-    #[instrument(skip(self, f), level = "debug")]
-    pub fn probe<R, F>(&self, f: F) -> R
-    where
-        F: FnOnce(&CombinedSnapshot<'tcx>) -> R,
-    {
-        let snapshot = self.start_snapshot();
-        let r = f(&snapshot);
-        self.rollback_to(snapshot);
-        r
-    }
-
-    /// Scan the constraints produced since `snapshot` and check whether
-    /// we added any region constraints.
-    pub fn region_constraints_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'tcx>) -> bool {
-        self.inner
-            .borrow_mut()
-            .unwrap_region_constraints()
-            .region_constraints_added_in_snapshot(&snapshot.undo_snapshot)
-    }
-
-    pub fn opaque_types_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'tcx>) -> bool {
-        self.inner.borrow().undo_log.opaque_types_in_snapshot(&snapshot.undo_snapshot)
-    }
-
     pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, expected: T, actual: T) -> bool
     where
         T: at::ToTrace<'tcx>,

compiler/rustc_infer/src/infer/opaque_types/table.rs

@@ -1,7 +1,7 @@
 use rustc_data_structures::undo_log::UndoLogs;
 use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey, Ty};
 
-use crate::infer::{InferCtxtUndoLogs, UndoLog};
+use crate::infer::snapshot::undo_log::{InferCtxtUndoLogs, UndoLog};
 
 use super::{OpaqueTypeDecl, OpaqueTypeMap};
 

compiler/rustc_infer/src/infer/outlives/obligations.rs

@@ -63,9 +63,8 @@ use crate::infer::outlives::components::{push_outlives_components, Component};
 use crate::infer::outlives::env::RegionBoundPairs;
 use crate::infer::outlives::verify::VerifyBoundCx;
 use crate::infer::resolve::OpportunisticRegionResolver;
-use crate::infer::{
-    self, GenericKind, InferCtxt, RegionObligation, SubregionOrigin, UndoLog, VerifyBound,
-};
+use crate::infer::snapshot::undo_log::UndoLog;
+use crate::infer::{self, GenericKind, InferCtxt, RegionObligation, SubregionOrigin, VerifyBound};
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::undo_log::UndoLogs;
 use rustc_middle::mir::ConstraintCategory;

compiler/rustc_infer/src/infer/region_constraints/leak_check.rs

@@ -1,9 +1,7 @@
 use super::*;
-use crate::infer::CombinedSnapshot;
-use rustc_data_structures::{
-    fx::FxIndexMap,
-    graph::{scc::Sccs, vec_graph::VecGraph},
-};
+use crate::infer::snapshot::CombinedSnapshot;
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::graph::{scc::Sccs, vec_graph::VecGraph};
 use rustc_index::Idx;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::relate::RelateResult;

compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -3,9 +3,8 @@
 use self::CombineMapType::*;
 use self::UndoLog::*;
 
-use super::{
-    InferCtxtUndoLogs, MiscVariable, RegionVariableOrigin, Rollback, Snapshot, SubregionOrigin,
-};
+use super::{MiscVariable, RegionVariableOrigin, Rollback, SubregionOrigin};
+use crate::infer::snapshot::undo_log::{InferCtxtUndoLogs, Snapshot};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
@@ -360,7 +359,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     ///
     /// Not legal during a snapshot.
     pub fn into_infos_and_data(self) -> (VarInfos, RegionConstraintData<'tcx>) {
-        assert!(!UndoLogs::<super::UndoLog<'_>>::in_snapshot(&self.undo_log));
+        assert!(!UndoLogs::<UndoLog<'_>>::in_snapshot(&self.undo_log));
         (mem::take(&mut self.storage.var_infos), mem::take(&mut self.storage.data))
     }
 
@@ -377,7 +376,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     ///
     /// Not legal during a snapshot.
     pub fn take_and_reset_data(&mut self) -> RegionConstraintData<'tcx> {
-        assert!(!UndoLogs::<super::UndoLog<'_>>::in_snapshot(&self.undo_log));
+        assert!(!UndoLogs::<UndoLog<'_>>::in_snapshot(&self.undo_log));
 
         // If you add a new field to `RegionConstraintCollector`, you
         // should think carefully about whether it needs to be cleared

compiler/rustc_infer/src/infer/relate/higher_ranked.rs

@@ -1,7 +1,7 @@
 //! Helper routines for higher-ranked things. See the `doc` module at
 //! the end of the file for details.
 
-use crate::infer::CombinedSnapshot;
+use crate::infer::snapshot::CombinedSnapshot;
 use crate::infer::InferCtxt;
 use rustc_middle::ty::fold::FnMutDelegate;
 use rustc_middle::ty::relate::RelateResult;

compiler/rustc_infer/src/infer/snapshot/fudge.rs

@@ -2,9 +2,9 @@ use rustc_middle::infer::unify_key::{ConstVariableOriginKind, ConstVariableValue
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid};
 
-use super::type_variable::TypeVariableOrigin;
-use super::InferCtxt;
-use super::{ConstVariableOrigin, RegionVariableOrigin, UnificationTable};
+use crate::infer::type_variable::TypeVariableOrigin;
+use crate::infer::InferCtxt;
+use crate::infer::{ConstVariableOrigin, RegionVariableOrigin, UnificationTable};
 
 use rustc_data_structures::snapshot_vec as sv;
 use rustc_data_structures::unify as ut;

compiler/rustc_infer/src/infer/snapshot/mod.rs

@@ -0,0 +1,102 @@
+use super::region_constraints::RegionSnapshot;
+use super::InferCtxt;
+use rustc_data_structures::undo_log::UndoLogs;
+use rustc_middle::ty;
+
+mod fudge;
+pub(crate) mod undo_log;
+
+use undo_log::{Snapshot, UndoLog};
+
+#[must_use = "once you start a snapshot, you should always consume it"]
+pub struct CombinedSnapshot<'tcx> {
+    pub(super) undo_snapshot: Snapshot<'tcx>,
+    region_constraints_snapshot: RegionSnapshot,
+    universe: ty::UniverseIndex,
+}
+
+impl<'tcx> InferCtxt<'tcx> {
+    pub fn in_snapshot(&self) -> bool {
+        UndoLogs::<UndoLog<'tcx>>::in_snapshot(&self.inner.borrow_mut().undo_log)
+    }
+
+    pub fn num_open_snapshots(&self) -> usize {
+        UndoLogs::<UndoLog<'tcx>>::num_open_snapshots(&self.inner.borrow_mut().undo_log)
+    }
+
+    fn start_snapshot(&self) -> CombinedSnapshot<'tcx> {
+        debug!("start_snapshot()");
+
+        let mut inner = self.inner.borrow_mut();
+
+        CombinedSnapshot {
+            undo_snapshot: inner.undo_log.start_snapshot(),
+            region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
+            universe: self.universe(),
+        }
+    }
+
+    #[instrument(skip(self, snapshot), level = "debug")]
+    fn rollback_to(&self, snapshot: CombinedSnapshot<'tcx>) {
+        let CombinedSnapshot { undo_snapshot, region_constraints_snapshot, universe } = snapshot;
+
+        self.universe.set(universe);
+
+        let mut inner = self.inner.borrow_mut();
+        inner.rollback_to(undo_snapshot);
+        inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot);
+    }
+
+    #[instrument(skip(self, snapshot), level = "debug")]
+    fn commit_from(&self, snapshot: CombinedSnapshot<'tcx>) {
+        let CombinedSnapshot { undo_snapshot, region_constraints_snapshot: _, universe: _ } =
+            snapshot;
+
+        self.inner.borrow_mut().commit(undo_snapshot);
+    }
+
+    /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
+    #[instrument(skip(self, f), level = "debug")]
+    pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
+    where
+        F: FnOnce(&CombinedSnapshot<'tcx>) -> Result<T, E>,
+    {
+        let snapshot = self.start_snapshot();
+        let r = f(&snapshot);
+        debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
+        match r {
+            Ok(_) => {
+                self.commit_from(snapshot);
+            }
+            Err(_) => {
+                self.rollback_to(snapshot);
+            }
+        }
+        r
+    }
+
+    /// Execute `f` then unroll any bindings it creates.
+    #[instrument(skip(self, f), level = "debug")]
+    pub fn probe<R, F>(&self, f: F) -> R
+    where
+        F: FnOnce(&CombinedSnapshot<'tcx>) -> R,
+    {
+        let snapshot = self.start_snapshot();
+        let r = f(&snapshot);
+        self.rollback_to(snapshot);
+        r
+    }
+
+    /// Scan the constraints produced since `snapshot` and check whether
+    /// we added any region constraints.
+    pub fn region_constraints_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'tcx>) -> bool {
+        self.inner
+            .borrow_mut()
+            .unwrap_region_constraints()
+            .region_constraints_added_in_snapshot(&snapshot.undo_snapshot)
+    }
+
+    pub fn opaque_types_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'tcx>) -> bool {
+        self.inner.borrow().undo_log.opaque_types_in_snapshot(&snapshot.undo_snapshot)
+    }
+}

compiler/rustc_infer/src/traits/project.rs

@@ -2,7 +2,7 @@
 
 use super::PredicateObligation;
 
-use crate::infer::InferCtxtUndoLogs;
+use crate::infer::snapshot::undo_log::InferCtxtUndoLogs;
 
 use rustc_data_structures::{
     snapshot_map::{self, SnapshotMapRef, SnapshotMapStorage},