Remove isTrackableRef check in BiTypeMap.backward

Author: bracevac

Diff for: compiler/src/dotty/tools/dotc/cc/Setup.scala

@@ -570,7 +570,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
               // For example, `(x: T, y: x.f.type) => Unit`. In this case, when we
               // substitute `x.f.type`, `x` becomes a `TermParamRef`. But the new method
               // type is still under initialization and `paramInfos` is still `null`,
-              // so the new `NamedType` will not have a denoation.
+              // so the new `NamedType` will not have a denotation.
               def adaptedInfo(psym: Symbol, info: mt.PInfo): mt.PInfo = mt.companion match
                 case mtc: MethodTypeCompanion => mtc.adaptParamInfo(psym, info).asInstanceOf[mt.PInfo]
                 case _ => info

Diff for: compiler/src/dotty/tools/dotc/core/Types.scala

@@ -6070,22 +6070,11 @@ object Types extends TypeUtils {
     def inverse: BiTypeMap
 
     /** A restriction of this map to a function on tracked CaptureRefs */
-    def forward(ref: CaptureRef): CaptureRef =
-      val result = this(ref)
-      /*def ensureTrackable(tp: Type): CaptureRef = tp match
-        case tp: CaptureRef =>
-          if tp.isTrackableRef then tp
-          else ensureTrackable(tp.underlying)
-        case tp: TypeAlias =>
-          ensureTrackable(tp.alias)
-        case _ =>
-          assert(false, i"not a trackable captureRef ref: $result, ${result.underlyingIterator.toList}")
-      ensureTrackable(result)*/
-      result.asInstanceOf[CaptureRef]
+    def forward(ref: CaptureRef): CaptureRef = this(ref).asInstanceOf[CaptureRef]
 
     /** A restriction of the inverse to a function on tracked CaptureRefs */
     def backward(ref: CaptureRef): CaptureRef = inverse(ref) match
-      case result: CaptureRef if result.isTrackableRef => result
+      case result: CaptureRef => result
   end BiTypeMap
 
   abstract class TypeMap(implicit protected var mapCtx: Context)