[unstable-rust] Use ATPIT in txn check types.

all-is-cubes/src/behavior.rs

@@ -575,7 +575,7 @@ impl<H: BehaviorHost> BehaviorSetTransaction<H> {
 
 impl<H: BehaviorHost> Transaction for BehaviorSetTransaction<H> {
     type Target = BehaviorSet<H>;
-    type CommitCheck = CommitCheck;
+    type CommitCheck = impl fmt::Debug;
     type Output = transaction::NoOutput;
     type Mismatch = BehaviorTransactionMismatch;
 
@@ -619,9 +619,11 @@ impl<H: BehaviorHost> Transaction for BehaviorSetTransaction<H> {
     fn commit(
         &self,
         target: &mut BehaviorSet<H>,
-        _: Self::CommitCheck,
+        check: Self::CommitCheck,
         _outputs: &mut dyn FnMut(Self::Output),
     ) -> Result<(), transaction::CommitError> {
+        let CommitCheck { _private: () } = check;
+
         for (key, replacement) in &self.replace {
             match &replacement.new {
                 Some(new) => {
@@ -677,7 +679,7 @@ impl<H: BehaviorHost> Transaction for BehaviorSetTransaction<H> {
 }
 
 impl<H: BehaviorHost> transaction::Merge for BehaviorSetTransaction<H> {
-    type MergeCheck = MergeCheck;
+    type MergeCheck = impl fmt::Debug;
     type Conflict = BehaviorTransactionConflict;
 
     fn check_merge(&self, other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {
@@ -692,7 +694,9 @@ impl<H: BehaviorHost> transaction::Merge for BehaviorSetTransaction<H> {
         Ok(MergeCheck { _private: () })
     }
 
-    fn commit_merge(&mut self, other: Self, _: Self::MergeCheck) {
+    fn commit_merge(&mut self, other: Self, check: Self::MergeCheck) {
+        let MergeCheck { _private: () } = check;
+
         self.replace.extend(other.replace);
         self.insert.extend(other.insert);
     }

all-is-cubes/src/block/block_def.rs

@@ -317,7 +317,7 @@ impl BlockDefTransaction {
 
 impl Transaction for BlockDefTransaction {
     type Target = BlockDef;
-    type CommitCheck = ();
+    type CommitCheck = impl fmt::Debug;
     type Output = transaction::NoOutput;
     type Mismatch = BlockDefMismatch;
 
@@ -345,7 +345,7 @@ impl Transaction for BlockDefTransaction {
 }
 
 impl transaction::Merge for BlockDefTransaction {
-    type MergeCheck = ();
+    type MergeCheck = impl fmt::Debug;
     type Conflict = BlockDefConflict;
 
     fn check_merge(&self, other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {

all-is-cubes/src/character.rs

@@ -725,11 +725,7 @@ impl CharacterTransaction {
 #[allow(clippy::type_complexity)]
 impl Transaction for CharacterTransaction {
     type Target = Character;
-    type CommitCheck = (
-        <BodyTransaction as Transaction>::CommitCheck,
-        <InventoryTransaction as Transaction>::CommitCheck,
-        <BehaviorSetTransaction<Character> as Transaction>::CommitCheck,
-    );
+    type CommitCheck = impl fmt::Debug;
     type Output = transaction::NoOutput;
     type Mismatch = CharacterTransactionMismatch;
 
@@ -781,11 +777,7 @@ impl Transaction for CharacterTransaction {
 }
 
 impl Merge for CharacterTransaction {
-    type MergeCheck = (
-        <BodyTransaction as Merge>::MergeCheck,
-        <InventoryTransaction as Merge>::MergeCheck,
-        <BehaviorSetTransaction<Character> as Merge>::MergeCheck,
-    );
+    type MergeCheck = impl fmt::Debug;
     type Conflict = CharacterTransactionConflict;
 
     fn check_merge(&self, other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {

all-is-cubes/src/inv/inventory.rs

@@ -5,6 +5,7 @@ use alloc::boxed::Box;
 use alloc::collections::BTreeMap;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
+use core::fmt;
 use core::num::NonZeroU16;
 
 use crate::block::Block;
@@ -366,14 +367,14 @@ impl InventoryTransaction {
 
 impl Transaction for InventoryTransaction {
     type Target = Inventory;
-    type CommitCheck = Option<InventoryCheck>;
+    type CommitCheck = impl fmt::Debug;
     type Output = InventoryChange;
     type Mismatch = InventoryMismatch;
 
     fn check(&self, inventory: &Inventory) -> Result<Self::CommitCheck, Self::Mismatch> {
         // Don't do the expensive copy if we have one already
         if self.replace.is_empty() && self.insert.is_empty() {
-            return Ok(None);
+            return Ok(None::<InventoryCheck>);
         }
 
         // The simplest bulletproof algorithm to ensure we're stacking everything right
@@ -441,7 +442,7 @@ impl Transaction for InventoryTransaction {
 }
 
 impl Merge for InventoryTransaction {
-    type MergeCheck = ();
+    type MergeCheck = impl fmt::Debug;
     type Conflict = InventoryConflict;
 
     fn check_merge(&self, other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {

all-is-cubes/src/lib.rs

@@ -1,3 +1,4 @@
+#![feature(impl_trait_in_assoc_type)]
 #![feature(never_type)]
 
 //! All is Cubes is a game/engine for worlds made of cubical blocks, where the blocks

all-is-cubes/src/physics/body.rs

@@ -709,7 +709,7 @@ impl transaction::Transactional for Body {
 
 impl Transaction for BodyTransaction {
     type Target = Body;
-    type CommitCheck = ();
+    type CommitCheck = impl fmt::Debug;
     type Output = transaction::NoOutput;
     type Mismatch = BodyMismatch;
 
@@ -730,7 +730,7 @@ impl Transaction for BodyTransaction {
 }
 
 impl transaction::Merge for BodyTransaction {
-    type MergeCheck = ();
+    type MergeCheck = impl fmt::Debug;
     type Conflict = core::convert::Infallible;
 
     fn check_merge(&self, _other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {

all-is-cubes/src/space/space_txn.rs

@@ -173,7 +173,7 @@ impl SpaceTransaction {
 
 impl Transaction for SpaceTransaction {
     type Target = Space;
-    type CommitCheck = <BehaviorSetTransaction<Space> as Transaction>::CommitCheck;
+    type CommitCheck = impl fmt::Debug;
     type Output = NoOutput;
     type Mismatch = SpaceTransactionMismatch;
 
@@ -298,7 +298,7 @@ impl Transaction for SpaceTransaction {
 }
 
 impl Merge for SpaceTransaction {
-    type MergeCheck = <BehaviorSetTransaction<Space> as Merge>::MergeCheck;
+    type MergeCheck = impl fmt::Debug;
     type Conflict = SpaceTransactionConflict;
 
     fn check_merge(&self, other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {
@@ -566,6 +566,7 @@ impl CubeTransaction {
 }
 
 impl Merge for CubeTransaction {
+    /// Not opaque because [`SpaceTransaction`] uses it
     type MergeCheck = CubeMergeCheck;
     type Conflict = CubeConflict;
 

all-is-cubes/src/transaction.rs

@@ -42,7 +42,7 @@ pub trait Transaction: Merge {
     /// This may be used to pass precalculated values to speed up the commit phase,
     /// or even lock guards or similar, but also makes it slightly harder to accidentally
     /// call `commit` without `check`.
-    type CommitCheck: 'static;
+    type CommitCheck: fmt::Debug + 'static;
 
     /// The results of a [`Transaction::commit()`] or [`Transaction::execute()`].
     /// Each commit may produce any number of these messages.
@@ -144,7 +144,7 @@ pub trait Merge: Sized {
     /// Type of a value passed from [`Merge::check_merge`] to [`Merge::commit_merge`].
     /// This may be used to pass precalculated values to speed up the merge phase,
     /// but also makes it difficult to accidentally merge without checking.
-    type MergeCheck: 'static;
+    type MergeCheck: fmt::Debug + 'static;
 
     /// Error type giving the reason why a merge was not possible.
     ///

all-is-cubes/src/universe/universe_txn.rs

@@ -87,6 +87,15 @@ where
     check: <O::Transaction as Transaction>::CommitCheck,
 }
 
+impl<O> fmt::Debug for TransactionInUniverseCheck<O>
+where
+    O: Transactional + 'static,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.check.fmt(f)
+    }
+}
+
 impl<O> Merge for TransactionInUniverse<O>
 where
     O: Transactional + 'static,
@@ -208,18 +217,18 @@ pub struct UniverseTransaction {
 }
 
 // TODO: Benchmark cheaper HashMaps / using BTreeMap here
-#[doc(hidden)] // Almost certainly will never need to be used explicitly
 #[derive(Debug)]
+#[doc(hidden)] // Almost certainly will never need to be used explicitly
 pub struct UniverseMergeCheck {
     members: HbHashMap<Name, MemberMergeCheck>,
-    behaviors: behavior::MergeCheck,
+    behaviors: <behavior::BehaviorSetTransaction<Universe> as Merge>::MergeCheck,
 }
 #[doc(hidden)] // Almost certainly will never need to be used explicitly
 #[derive(Debug)]
-pub struct UniverseCommitCheck {
+struct UniverseCommitCheck {
     members: HbHashMap<Name, MemberCommitCheck>,
     anonymous_insertions: Vec<MemberCommitCheck>,
-    behaviors: behavior::CommitCheck,
+    behaviors: <behavior::BehaviorSetTransaction<Universe> as Transaction>::CommitCheck,
 }
 
 /// Transaction precondition error type for [`UniverseTransaction`].
@@ -467,7 +476,7 @@ impl From<AnyTransaction> for UniverseTransaction {
 
 impl Transaction for UniverseTransaction {
     type Target = Universe;
-    type CommitCheck = UniverseCommitCheck;
+    type CommitCheck = impl fmt::Debug;
     type Output = transaction::NoOutput;
     type Mismatch = UniverseMismatch;
 
@@ -577,7 +586,7 @@ impl Transaction for UniverseTransaction {
 }
 
 impl Merge for UniverseTransaction {
-    type MergeCheck = UniverseMergeCheck;
+    type MergeCheck = impl fmt::Debug;
     type Conflict = UniverseConflict;
 
     fn check_merge(&self, other: &Self) -> Result<Self::MergeCheck, Self::Conflict> {
@@ -605,10 +614,14 @@ impl Merge for UniverseTransaction {
             behaviors,
             universe_id,
         } = self;
+        let UniverseMergeCheck {
+            members: check_members,
+            behaviors: check_behaviors,
+        } = check;
 
-        members.commit_merge(other.members, check.members);
+        members.commit_merge(other.members, check_members);
         anonymous_insertions.extend(other.anonymous_insertions);
-        behaviors.commit_merge(other.behaviors, check.behaviors);
+        behaviors.commit_merge(other.behaviors, check_behaviors);
         transaction::merge_option(
             universe_id,
             other.universe_id,