Added apply methods to import selectors in Quotes #21225

[ghik]

Fixes #21225

[bishabosha]

Suggested change

	@experimental def apply(bound: Option[TypeTree]): GivenSelector
	@experimental def apply(bound: Option[TypeRepr]): GivenSelector

I would suggest internally wrapping the type in TypeTree with the default span

[ghik]

That would be inconsistent with unapply and the .bound accessor method. Is that a problem?

[jchyb]

TypeTree makes more sense to me too

[jchyb]

Thank you for submitting! The PR looks good, and in my opinion the use case is valid. I would only suggest adding a test, at least for GivenSelector and OmitSelector - I don't really know how we could test others. Here's what I came up with, based on the snippets submitted in #21225:
In tests/run-macros/i21225/Macro_1.scala:

//> using options -experimental

import scala.quoted.*

trait Codec[-T] { def print(): Unit }
object Codec {
  inline def derivedWithDeps[T](deps: Any): Codec[T] = ${derivedWithDepsImpl[T]('deps)}

  private def derivedWithDepsImpl[T](deps: Expr[Any])(using q: Quotes)(using Type[T]): Expr[Codec[T]] = {
    import q.reflect.*

    val givenSelector: Selector = GivenSelector(None)
    val theImport = Import(deps.asTerm, List(givenSelector))
    Block(List(theImport), '{scala.compiletime.summonInline[Codec[T]]}.asTerm).asExprOf[Codec[T]]
    /* import deps.given
     * summonInline[Codec[T]]
     */
  }

  inline def derivedWithDepsWithNamedOmitted[T](deps: Any): Codec[T] = ${derivedWithDepsWithNamedOmittedImpl[T]('deps)}

  private def derivedWithDepsWithNamedOmittedImpl[T](deps: Expr[Any])(using q: Quotes)(using Type[T]): Expr[Codec[T]] = {
    import q.reflect.*

    val givenSelector: Selector = GivenSelector(None)
    val omitSelector: Selector = OmitSelector("named")
    val theImport = Import(deps.asTerm, List(givenSelector, omitSelector))
    Block(List(theImport), '{scala.compiletime.summonInline[Codec[T]]}.asTerm).asExprOf[Codec[T]]
    /* import deps.{given, named => _}
     * summonInline[Codec[T]]
     */
  }
}

In tests/run-macros/i21225/Test_2.scala :

//> using options -experimental

import scala.quoted.*

sealed trait Foo
case class Bar() extends Foo
object CustomCodecs {
  given named: Codec[Bar] = new Codec[Bar]{ def print(): Unit = println("bar codec")}
  given Codec[Foo] = new Codec[Foo]{ def print(): Unit = println("foo codec") }
}

@main def Test =
  Codec.derivedWithDeps[Bar](CustomCodecs).print()
  Codec.derivedWithDepsWithNamedOmitted[Bar](CustomCodecs).print()

In tests/run-macros/i21225.check:

bar codec
foo codec

Sorry about the long wait, let me know if you have the time to add those, alternatively I can take this over.

[ghik]

@jchyb added tests as you suggested