Move FollowAliasesMap from CaptureOps to Types

Author: odersky

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

@@ -639,19 +639,6 @@ class CleanupRetains(using Context) extends TypeMap:
         RetainingType(tp, Nil, byName = annot.symbol == defn.RetainsByNameAnnot)
       case _ => mapOver(tp)
 
-/** A typemap that follows aliases and keeps their transformed results if
- *  there is a change.
- */
-trait FollowAliasesMap(using Context) extends TypeMap:
-  var follow = true    // Used for debugging so that we can compare results with and w/o following.
-  def mapFollowingAliases(t: Type): Type =
-    val t1 = t.dealiasKeepAnnots
-    if follow && (t1 ne t) then
-      val t2 = apply(t1)
-      if t2 ne t1 then t2
-      else t
-    else mapOver(t)
-
 /** An extractor for `caps.reachCapability(ref)`, which is used to express a reach
  *  capability as a tree in a @retains annotation.
  */

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -6168,6 +6168,18 @@ object Types extends TypeUtils {
 
   end BiTypeMap
 
+  /** A typemap that follows aliases and keeps their transformed results if
+  *  there is a change.
+  */
+  trait FollowAliasesMap(using Context) extends TypeMap:
+    def mapFollowingAliases(t: Type): Type =
+      val t1 = t.dealiasKeepAnnots
+      if t1 ne t then
+        val t2 = apply(t1)
+        if t2 ne t1 then t2
+        else t
+      else mapOver(t)
+
   abstract class TypeMap(implicit protected var mapCtx: Context)
   extends VariantTraversal with (Type => Type) { thisMap =>