Since 3.8.0-RC1, inline match with inlined values sometimes does not compile as it erases values that it accesses

[rmgk]

Compiler version

3.8.0-RC1 and newer (tested 3.8.1-RC1-bin-20251128-fe49539-NIGHTLY)
(compiles in 3.7.4)

Minimized code

Scastie: https://scastie.scala-lang.org/l4JwtPFxQBaKZqMFoAOzaA

object Test {
  inline def dispatch(inline v: Long | String) =
    inline v match
      case str: String => printString(str)
      case long: Long  => printLong(long)

  def printString(s: String) = println(s)
  def printLong(s: Long) = println(s)


  @main
  def run() =
    dispatch(System.nanoTime().toString)
    dispatch(s"${System.nanoTime().toString}")

}

Output

Compiling project (Scala 3.8.1-RC1-bin-20251128-fe49539-NIGHTLY, JVM (17))
[error] ./test.scala:14:5
[error] value str is unusable in method run because it refers to an erased expression
[error] in the selector of an inline match that reduces to
[error] 
[error] {
[error]   erased val $scrutinee2: String =
[error]     _root_.scala.StringContext.apply(["","" : String]*).s(
[error]       [System.nanoTime().toString() : Any]*)
[error]   erased val str: String = $scrutinee2
[error]   {
[error]     Test.printString(str)
[error]   }
[error] }
[error]     dispatch(s"${System.nanoTime().toString}")
[error]     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Expectation

For some reason, specifically when passing s"…" to the dispatch inline def directly, the above error happens. All other strings I tried to pass compile as expected.
Works fine if the parameter of the inline def is not inline.

[hamzaremmal]

For some reason, specifically when passing s"…" to the dispatch inline def directly, the above error happens. All other strings I tried to pass compile as expected.
Works fine if the parameter of the inline def is not inline.

Thanks for the bug report. The 3 interpolators as defined in the library are considered Erased by the compiler (but that's not new). In #24407, I'm trying to remove this old behaviour so it would be interesting to see first if that fixes this issue and second why it was triggered in the first place.