Ignore selection prototypes when typing type applications

[odersky]

Ignore selection prototypes at first when typing type applications. If we need them later for overloading disambiguation, reveal the ignored type.

The reason for doing this is that a selection might come from an extension method, and in this case we should not require the selected name as a member of the result.

This change breaks one test (overloading-specifity-2.scala) that explicitly tested that we don't consult implicit arguments for disambiguation since the expected type was a selection that already determined the outcome. This logic no longer holds. We have to see whether this change breaks any code in practice.

Fixes #23773

[odersky]

@hamzaremmal I am surprised to not see community build tasks in the task list. Where are they?

[hamzaremmal]

They are there, they just kick in later.

[hamzaremmal]

@WojciechMazur can we have an Open CB run on this PR? Thanks.

[WojciechMazur]

Sure, I'll schedule the build as soon as I'll fix some infra problems

[odersky]

This should be backported to 3.8.0 if it works but not to 3.3 since it involves a change in behavior.

[hamzaremmal]

This should be backported to 3.8.0 if it works but not to 3.3 since it involves a change in behavior.

Yes, the label is for 3.8.0, not 3.3.x

[hamzaremmal]

LGTM but I'll wait for the Open CB run result before approving.

[WojciechMazur]

Sorry for long delay but we had problems with OpenCB infra.
I've found 3 project that seems to be affected by this PR resulting in fail, but which do compile in latest nightly.

Here's the first reproduced issue from eikek/soidc

trait NumericDate
trait JWSDecoded[H]

trait StandardHeaderWrite[H]:
  def setAlgorithm(header: H, algorithm: Algorithm): H

object StandardHeaderWrite:
  def apply[H](using sh: StandardHeaderWrite[H]): StandardHeaderWrite[H] = ???
  // unused - required to reproduce
  def apply[H](setAlg: (H, Algorithm) => H): StandardHeaderWrite[H] = ???

final case class JWK(algorithm: Option[Algorithm])
sealed trait Algorithm

def Test[F[_], H](key: JWK, header: H)(using StandardHeaderWrite[H]) = {
  key.algorithm
    .map(StandardHeaderWrite[H].setAlgorithm(header, _))
    .getOrElse(header)
}

ompiling project (Scala 3.8.1-RC1-bin-20251120-60444cb, JVM (21))
[error] ./test.scala:17:10
[error] value setAlgorithm is not a member of ((H, Algorithm) => H) => StandardHeaderWrite[H]
[error]     .map(StandardHeaderWrite[H].setAlgorithm(header, _))
[error]          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

2 additional failed projects without reproduction, however these seem similar to existing issues fixed in current main

Project	Version	Build URL	Notes
kacperfkorban/guinep	0.1.1	Open CB logs	Similar to #23969 passed in main
paoloboni/binance-scala-client	1.6.1	Open CB logs	Probably the same as #24093 passes latest nightly

[odersky]

Thanks for the minimization! That looks like expected behavior after the change in this PR. In StandardHeaderWrite[H].setAlgorithm we are choosing the alternative without knowledge of the expected result type now. That would resolve to the second apply, since that second apply does not require an implicit parameter. But the chosen alternative does not match the selection prototype once it is revealed.

I can see one possible improvement of the PR: We could maybe retain the fact somehow that we expect some selection, to rule out the alternative where the next action would be an application. Let me try that.

[odersky]

I managed to make the minimizer compiler with some additional tweaks.