Fix nondeterministic private field ordering in Lifter

The private fields generated by the lifter had nondeterministic ordering
because they were built by iterating over Map values derived from Set
operations. Scala's Set and Map do not guarantee stable iteration order.

The fix uses sorted ordered lists (passedSymsOrdered, capturesOrdered,
passedDefnsOrdered, and new liftedObjsOrdered) to look up map values in
a deterministic order based on symbol UIDs, instead of iterating map
values directly.

Agent-Logs-Url: https://github.com/LPTK/mlscript/sessions/07ac81ed-dfff-467c-af13-4a25818d2faa

Author: Copilot

hkmc2/shared/src/main/scala/hkmc2/codegen/Lifter.scala

@@ -792,6 +792,7 @@ class Lifter(topLevelBlk: Block)(using State, Raise, Config):
     protected val liftedObjsSyms: Map[InnerSymbol, VarSymbol] = node.liftedObjSyms.map: s =>
         s -> VarSymbol(Tree.Ident(s.nme + "$"))
       .toMap
+    protected val liftedObjsOrdered: List[InnerSymbol] = node.liftedObjSyms.toList.sortBy(_.uid)
     override lazy val liftedObjsMap: Map[InnerSymbol, LocalPath] = liftedObjsSyms.map:
       case k -> v => k -> v.asLocalPath
 
@@ -806,6 +807,7 @@ class Lifter(topLevelBlk: Block)(using State, Raise, Config):
     protected val liftedObjsSyms: Map[InnerSymbol, TermSymbol] = node.liftedObjSyms.map: s =>
         s -> TermSymbol(syntax.ImmutVal, S(sym), Tree.Ident(s.nme + "$"))
       .toMap
+    protected val liftedObjsOrdered: List[InnerSymbol] = node.liftedObjSyms.toList.sortBy(_.uid)
     override lazy val liftedObjsMap: Map[InnerSymbol, LocalPath] = liftedObjsSyms.map:
       case k -> v => k -> v.asLocalPath
     protected def rewriteMethods(node: ScopeNode, methods: List[FunDefn])(using ctx: LifterCtxNew) =
@@ -879,7 +881,7 @@ class Lifter(topLevelBlk: Block)(using State, Raise, Config):
       val newCls = obj.cls.copy(
         ctor = ctorWithCap,
         preCtor = rewrittenPrector,
-        privateFields = captureSym :: liftedObjsSyms.values.toList ::: obj.cls.privateFields,
+        privateFields = captureSym :: liftedObjsOrdered.map(liftedObjsSyms) ::: obj.cls.privateFields,
         methods = newMtds,
       )(obj.cls.configOverride)
       LifterResult(newCls, rewriterCtor.extraDefns.toList ::: rewriterPreCtor.extraDefns.toList ::: extras)
@@ -898,7 +900,7 @@ class Lifter(topLevelBlk: Block)(using State, Raise, Config):
       val LifterResult(newMtds, extras) = rewriteMethods(node, obj.clsBody.methods)
       val newComp = obj.clsBody.copy(
         ctor = ctorWithCap,
-        privateFields = captureSym :: liftedObjsSyms.values.toList ::: obj.clsBody.privateFields,
+        privateFields = captureSym :: liftedObjsOrdered.map(liftedObjsSyms) ::: obj.clsBody.privateFields,
         methods = newMtds
       )
       LifterResult(newComp, rewriterCtor.extraDefns.toList ::: extras)
@@ -1040,9 +1042,11 @@ class Lifter(topLevelBlk: Block)(using State, Raise, Config):
           )
       .toMap
 
-    private val extraPrivSyms = 
-      liftedObjsSyms.values ++ passedSymsMap_.values.map(_.ts)
-      ++ capSymsMap_.values.map(_.ts) ++ defnSymsMap_.values.map(_.ts)
+    private lazy val extraPrivSyms: List[TermSymbol] = 
+      liftedObjsOrdered.map(liftedObjsSyms)
+      ::: passedDefnsOrdered.map(defnSymsMap_(_).ts)
+      ::: capturesOrdered.map(capSymsMap_(_).ts)
+      ::: passedSymsOrdered.map(passedSymsMap_(_).ts)
 
     override lazy val capturesOrdered: List[ScopedInfo] = reqCaptures.toList.sortBy(c => capSymsMap_(c).vs.uid)
 
@@ -1173,7 +1177,7 @@ class Lifter(topLevelBlk: Block)(using State, Raise, Config):
         k = syntax.Cls, // turn objects into classes
         ctor = ctorWithDefns,
         preCtor = rewrittenPrector,
-        privateFields = captureSym :: extraPrivSyms.toList ::: obj.cls.privateFields,
+        privateFields = captureSym :: extraPrivSyms ::: obj.cls.privateFields,
         methods = newMtds,
         auxParams = newAuxList
       )(obj.cls.configOverride)

hkmc2/shared/src/test/mlscript/lifter/ClassInFun.mls

@@ -157,9 +157,9 @@ f().foo()
 //│ };
 //│ define Good⁰ as class Good¹() {
 //│   private val Good$cap⁰;
+//│   private val scope0$cap⁰;
 //│   private val x¹;
 //│   private val y²;
-//│   private val scope0$cap⁰;
 //│   constructor Good²(scope0$cap, x, y) {
 //│     set scope0$cap⁰ = scope0$cap;
 //│     set x¹ = x;