opaque type selects different method with -from-tasty

[bishabosha]

Compiler version

3.0.0-RC1

Minimized code

package opaquetypes

object `package`:

  opaque type Foo = Double

  object Bar:

    class Baz(val i: Foo):
      def foo(that: Any): Boolean = that match
        // `Double.==` selected from source; `Any.==` selected `-from-tasty`
        case that1 @ (_: Baz) => Baz.this.i == that1.i
        case _ => true

Expectation

Double.== should also be selected with -from-tasty, the issue arises when if you actually select Double.== in unpickling then the checker does not expect it

[bishabosha]

@smarter this one is a problem because at the point of pickling, Baz.this.i.== resolves to the symbol Double.==, but at the point of unpickling qualType.findMember("==") would find Any.==, same with TreeChecker.

I would think TreeChecker should not find Any.==, this makes it a problem to encode selecting from an opaque type with SELECTin in #11210

Noteworthy is that when compiling from source TreeChecker has no problem with Double.==

[smarter]

Shouldn't findMember find both and pick the one from Double since it has the correct signature?

[bishabosha]

@smarter no, it gets NoDenotation

// compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
def accessibleDenot(qualType: Type, name: Name, sig: Signature, target: Name) = {
  val pre = ctx.typeAssigner.maybeSkolemizePrefix(qualType, name)
  val d = qualType.findMember(name, pre).atSignature(sig, target)
  val denot =
    if (!d.symbol.exists || d.symbol.isAccessibleFrom(pre)) d
    else qualType.findMember(name, pre, excluded = Private).atSignature(sig, target)
  report.echo(i"$qualType.$name unpickle from SELECT is denot $denot (sig is $sig)")
  denot
}

we get the log message

(Baz.this.i : opaquetypes.Foo).== unpickle from SELECT is denot NoDenotation (sig is Signature(List(scala.Double),scala.Boolean))

[smarter]

I think https://github.com/dotty-staging/dotty/commits/thisType-check fixes the problem, can you double-check and take care of integrating it in your PR (sameThis should probably be a method in ThisType...).

[bishabosha]

I think https://github.com/dotty-staging/dotty/commits/thisType-check fixes the problem, can you double-check and take care of integrating it in your PR (sameThis should probably be a method in ThisType...).

I just tried and it worked, very cool