Make captureSetofInfo cache in CaptureRefs depend on iteration count

Author: odersky

compiler/src/dotty/tools/dotc/cc/CaptureRef.scala

@@ -9,21 +9,30 @@ import typer.ErrorReporting.Addenda
 import util.common.alwaysTrue
 import scala.collection.mutable
 import CCState.*
-import Periods.NoRunId
+import Periods.{NoRunId, RunWidth}
 import compiletime.uninitialized
 import StdNames.nme
 import CaptureSet.VarState
 import Annotations.Annotation
 import config.Printers.capt
 
+object CaptureRef:
+  opaque type Validity = Int
+  def validId(runId: Int, iterId: Int): Validity =
+    runId + (iterId << RunWidth)
+  def currentId(using Context): Validity = validId(ctx.runId, ccState.iterCount)
+  val invalid: Validity = validId(NoRunId, 0)
+
 /** A trait for references in CaptureSets. These can be NamedTypes, ThisTypes or ParamRefs,
  *  as well as three kinds of AnnotatedTypes representing readOnly, reach, and maybe capabilities.
  *  If there are several annotations they come with an order:
  *  `*` first, `.rd` next, `?` last.
  */
 trait CaptureRef extends TypeProxy, ValueType:
+  import CaptureRef.*
+
   private var myCaptureSet: CaptureSet | Null = uninitialized
-  private var myCaptureSetRunId: Int = NoRunId
+  private var myCaptureSetValid: Validity = invalid
   private var mySingletonCaptureSet: CaptureSet.Const | Null = null
   private var myDerivedRefs: List[AnnotatedType] = Nil
 
@@ -130,7 +139,7 @@ trait CaptureRef extends TypeProxy, ValueType:
 
   /** The capture set of the type underlying this reference */
   final def captureSetOfInfo(using Context): CaptureSet =
-    if ctx.runId == myCaptureSetRunId then myCaptureSet.nn
+    if myCaptureSetValid == currentId then myCaptureSet.nn
     else if myCaptureSet.asInstanceOf[AnyRef] eq CaptureSet.Pending then CaptureSet.empty
     else
       myCaptureSet = CaptureSet.Pending
@@ -143,11 +152,11 @@ trait CaptureRef extends TypeProxy, ValueType:
         myCaptureSet = null
       else
         myCaptureSet = computed
-        myCaptureSetRunId = ctx.runId
+        myCaptureSetValid = currentId
       computed
 
   final def invalidateCaches() =
-    myCaptureSetRunId = NoRunId
+    myCaptureSetValid = invalid
 
   /**  x subsumes x
    *   x =:= y       ==>  x subsumes y

compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala

@@ -268,7 +268,9 @@ class CheckCaptures extends Recheck, SymTransformer:
       needAnotherRun = false
       resetNuTypes()
       todoAtPostCheck.clear()
-      for (sym, completer) <- completed do sym.info = completer
+      for (sym, completer) <- completed do
+        sym.info = completer
+        sym.resetFlag(Touched)
       completed.clear()
 
     extension [T <: Tree](tree: T)