Fix scala-js/scala-js#4801: Rebase the super JS type as seen from the this type in JS super call.

When doing a super call to a method of a path-dependent JS super
class, the `superClass.typeRef` is only valid as seen from the
super class' thisType. We need to rebase it with `asSeenFrom` to
be in the context of the current class' thisType.

Forward port of the upstream commit
scala-js/scala-js@3cef9d0

Author: sjrd

compiler/src/dotty/tools/dotc/transform/sjs/ExplicitJSClasses.scala

@@ -637,7 +637,11 @@ class ExplicitJSClasses extends MiniPhase with InfoTransformer { thisPhase =>
   private def maybeWrapSuperCallWithContextualJSClassValue(tree: Tree)(using Context): Tree = {
     methPart(tree) match {
       case Select(sup: Super, _) if isInnerOrLocalJSClass(sup.symbol.asClass.superClass) =>
-        wrapWithContextualJSClassValue(sup.symbol.asClass.superClass.typeRef)(tree)
+        val superClass = sup.symbol.asClass.superClass
+        val jsClassTypeInSuperClass = superClass.typeRef
+        // scala-js#4801 Rebase the super class type on the current class' this type
+        val jsClassTypeAsSeenFromThis = jsClassTypeInSuperClass.asSeenFrom(currentClass.thisType, superClass)
+        wrapWithContextualJSClassValue(jsClassTypeAsSeenFromThis)(tree)
       case _ =>
         tree
     }