3.1.2 compiler emits an error - Type argument B does not conform to lower bound String for export of a Seq value

[chungonn]

The following code compiles in Scala 3.1.1 and with Scala 3.1.2, the compiler emits the following error - Type argument B does not conform to lower bound String

object Test{
  
  val xs: Seq[String] = List("Apple", "Orange", "Pear")
  export xs.*
  
} 

Test.head

[som-snytt]

It looks like the bound on a default arg method.

    final def lastIndexOf[B >: String](elem: B, end: Int): Int = X.xs.lastIndexOf[B](elem, end)
    final def lastIndexOf$default$2[B >: A]: Int @uncheckedVariance = X.xs.lastIndexOf$default$2[B]

Or, minimized

class C[A] {
  def f[B >: A](x: Int = 42): A = ???
}
object X {
  val c = new C[String]
  export c.*
}

which looks like

  @SourceFile("exp0.scala") class C[A >: Nothing <: Any]() extends Object() {
    A
    def f[B >: C.this.A <: Any](x: Int): C.this.A = ???
    def f$default$1[B >: C.this.A <: Any]: Int @uncheckedVariance = 42
  }
  final lazy module val X: X = new X()
  @SourceFile("exp0.scala") final module class X() extends Object() { this: X.type =>
    private def writeReplace(): AnyRef = new scala.runtime.ModuleSerializationProxy(classOf[X.type])
    val c: C[String] = new C[String]()
    export X.c.*
    final def f[B >: String](x: Int): String = X.c.f[B](x)
    final def f$default$1[B >: A]: Int @uncheckedVariance = X.c.f$default$1[B]
  }

For an error in synthetic code where the caret isn't helpful, it would be nice if the message could capture enough context (such as the enclosing definition) to pretty print with the caret.

[chungonn]

My code uses only the Seq#head method and when I did the export xs.head my application compiles. I suppose the method resolution for export in Scala 3.1.2 is different Scala 3.1.1

I realised the export xs.* declaration alone has compilation error.

[som-snytt]

My comment explains that the export exports the wrong signature for the default arg methods. The signature includes the type param of the "source" method even if not used, and the bound should be [B :> String] in the examples.

[chungonn]

Noted with thanks. I thought I could provide more context on my export usage :)