Scala 3消除staging.Compiler重复设置-experimental标志提示的方法

运行以下Scala 3测试代码时，频繁出现“Flag -experimental set repeatedly”提示（功能本身正常）。由于@experimental注解需要启用-experimental标志，移除(using settings)会导致测试失败，请问如何消除该提示？

import org.scalatest.flatspec.AnyFlatSpec
import org.scalatest.matchers.should.Matchers.shouldBe
import scala.quoted.{Expr, staging}
import scala.annotation.experimental


final class MyTest extends AnyFlatSpec:
  import MyTest.fun

  private val settings = staging.Compiler.Settings.make(compilerArgs="-experimental"::Nil)
  private given staging.Compiler = staging.Compiler.make(getClass.getClassLoader)(using settings)

  "subject" should "behave as expected" in:
    def test(value: Int): Unit =
      staging.run('{fun(${Expr(value)})}) shouldBe value + 1
    test(1)
    test(2)

private object MyTest:
  @experimental
  def fun(x: Int): Int = x + 1

出现该提示的核心原因是staging.Compiler实例被重复创建，导致-experimental参数被多次添加。以下是几种可行的解决方式：

方式一：复用单一Compiler实例 #

将Compiler实例的创建移到测试类的伴生对象中，确保整个测试流程只初始化一次Compiler，避免重复设置参数：

import org.scalatest.flatspec.AnyFlatSpec
import org.scalatest.matchers.should.Matchers.shouldBe
import scala.quoted.{Expr, staging}
import scala.annotation.experimental


final class MyTest extends AnyFlatSpec:
  import MyTest.{fun, compiler}

  given staging.Compiler = compiler

  "subject" should "behave as expected" in:
    def test(value: Int): Unit =
      staging.run('{fun(${Expr(value)})}) shouldBe value + 1
    test(1)
    test(2)

private object MyTest:
  @experimental
  def fun(x: Int): Int = x + 1

  // 仅初始化一次Compiler实例
  private val settings = staging.Compiler.Settings.make(compilerArgs = "-experimental" :: Nil)
  val compiler: staging.Compiler = staging.Compiler.make(getClass.getClassLoader)(using settings)

方式二：全局启用experimental标志 #

通过JVM系统属性全局开启-experimental，无需在代码中手动传递参数给staging Compiler：

方式1：运行测试时添加JVM参数 #

sbt -Dscala.experimental=true test

方式2：在build.sbt中配置 #

Test / javaOptions += "-Dscala.experimental=true"

修改后代码可简化为：

private given staging.Compiler = staging.Compiler.make(getClass.getClassLoader)

方式三：禁用测试并行执行 #

若使用ScalaTest的并行测试特性，多个测试类实例会各自创建Compiler，导致重复提示。可通过以下方式禁用并行：

方式1：给测试类添加注解 #

import org.scalatest.DoNotDiscover
import org.scalatest.flatspec.AnyFlatSpec

@DoNotDiscover
final class MyTest extends AnyFlatSpec:
  // 原有代码...

方式2：在build.sbt中全局配置 #

Test / parallelExecution := false

内容的提问来源于stack exchange，提问作者Koosha