"asSeenFrom" in Scala 3

[xuwei-k]

I need asSeenFrom method similar to Scala 2 reflection API. but I could not found in Scala 3 API.

https://github.com/scala/scala/blob/18ce8d410b57f30f4161896b49b03d2d3e7b0401/src/reflect/scala/reflect/api/Types.scala#L246

dotty.tools.dotc.core.TypeOps has asSeenFrom but I think we can not use that from quotes API.

https://github.com/lampepfl/dotty/blob/53f5531e7e31eca02b3db158c8c384e713b4542a/compiler/src/dotty/tools/dotc/core/TypeOps.scala#L30

Is there more better solution to avoid compiler internal api.

please see following example.

xuwei-k/Scala-asSeenFrom@8300806

Thanks.

[smarter]

Does this work for your usecase?
https://github.com/lampepfl/dotty/blob/53f5531e7e31eca02b3db158c8c384e713b4542a/library/src/scala/quoted/Quotes.scala#L2590-L2594
(It's implemented using asSeenFrom: https://github.com/lampepfl/dotty/blob/53f5531e7e31eca02b3db158c8c384e713b4542a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala#L1740-L1741)

[xuwei-k]

memberType does not work in my usecase. because it fixed cls = member.owner param.

[smarter]

Can you give a concrete example of what output you expect and what output you get with memberType?

[xuwei-k]

please see following example.

xuwei-k/Scala-asSeenFrom@8300806

🙏

class MyAnnotation(clazz: Class[?]) extends StaticAnnotation

trait D[E]

class A[B] {
  @MyAnnotation(clazz = classOf[D[B]])
  def x: B = ???
}

class C extends A[Int]

I expect D[Int].

xuwei-k/Scala-asSeenFrom@64784c7

memberType result

ClassInfo(ThisType(TypeRef(NoPrefix,module class example)), class C, List(AppliedType(TypeRef(ThisType(TypeRef(NoPrefix,module class example)),class A),List(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),Int)))))

ClassInfo(ThisType(TypeRef(NoPrefix,module class example)), class A, List(TypeRef(ThisType(TypeRef(NoPrefix,module class lang)),class Object)))

[smarter]

Ah I see, you're interested in the type of' D[B] in the scope of C, indeed it seems like we're missing an API for doing that /cc @nicolasstucki, you could open an issue for this (and maybe even a PR with a proposed API addition).