在从Scala 2.13迁移到3.2时丢失

Question

我一直按照迁移指南上的指示行事，但没有成功。我已经有了一个跨编译的SBT项目，没有问题，有以下build.sbt

lazy val ttv = (project in file("."))
  .settings(
    name := "Tame the Void",
    version := "0.1",
    scalaVersion := "3.2.0",
    crossScalaVersions := Seq("2.13.6", "3.2.0"),
    libraryDependencies ++= mainDependencies ++ testDependencies,
    scalacOptions := {
      Seq(
        "-encoding",
        "UTF-8",
        "-feature",
        "-language:implicitConversions",
        // disabled during the migration
        // "-Xfatal-warnings"
      ) ++
        (CrossVersion.partialVersion(scalaVersion.value) match {
          case Some((3, _)) =>
            println("Using 3.0 flags --------------------")
            Seq(
              "-unchecked",
              "-source:3.2-migration",
              "-indent",
              "-rewrite"
            )
          case _ =>
            println("Using 2.13 flags --------------------")
            Seq(
              "-deprecation",
              "-Wunused:imports,privates,locals",
              "-Wvalue-discard"
            )
        })
    }
  )

所有Scala2.13代码都编译得很好，但是我添加了一个scala 3特定的文件来测试：src/main/scala-3/Scala3test.scala

object Scala3Test extends App {

  given x: Int = 1
  def f(using x: Int) = println(x)
  f

  given Ordering[Int] with
    override def compare(x: Int, y: Int): Int = if x < y then 1 else -1

  def g(using x: Ordering[Int]) = println(x.compare(3, 4))
  g
}

如果我从头创建Scala 3项目，这个测试运行得很好，但是这里似乎根本不识别新的语法：

compile
Using 3.0 flags --------------------
[info] compiling 102 Scala sources to D:\Projects\4x-scala\target\scala-3.2.0\classes ...
[warn] Flag -source set repeatedly
[error] -- [E018] Syntax Error: D:\Projects\4x-scala\src\main\scala-3\Scala3Test.scala:3:9 
[error] 3 |  given x: Int = 1
[error]   |         ^
[error]   |         expression expected but : found
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] -- Error: D:\Projects\4x-scala\src\main\scala-3\Scala3Test.scala:3:15 ----------
[error] 3 |  given x: Int = 1
[error]   |               ^
[error]   |               end of statement expected but '=' found
[error] -- [E018] Syntax Error: D:\Projects\4x-scala\src\main\scala-3\Scala3Test.scala:7:16 
[error] 7 |  given Ordering[Int] with
[error]   |                ^
[error]   |                expression expected but '[' found
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] -- [E006] Not Found Error: D:\Projects\4x-scala\src\main\scala-3\Scala3Test.scala:3:2 
[error] 3 |  given x: Int = 1
[error]   |  ^^^^^
[error]   |  Not found: given
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] -- Error: D:\Projects\4x-scala\src\main\scala-3\Scala3Test.scala:5:3 -----------
[error] 5 |  f
[error]   |   ^
[error]   |No given instance of type Int was found for parameter x of method f in object Scala3Test
[error] -- [E006] Not Found Error: D:\Projects\4x-scala\src\main\scala-3\Scala3Test.scala:7:2 
[error] 7 |  given Ordering[Int] with
[error]   |  ^^^^^
[error]   |  Not found: given
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[warn] one warning found
[error] 6 errors found

我的理解是，基于SBT的交叉构建文档应该在3.2.0中构建该文件并识别语法。它也没有重写任何语法(应该给出"-indent“、"-rewrite”标志)。

任何指示都将不胜感激。

Answer 1

你在某个地方设置了错误的旗子。请允许我表明：

$ ls
Scala3Test.scala build.sbt
$ cat build.sbt
name := "scala-3-test"
scalaVersion := "3.2.0"
scalacOptions += "-source:3.0-migration"
$ sbt compile
[info] compiling 1 Scala source to ***/target/scala-3.2.0/classes ...
[error] -- [E018] Syntax Error: ***/Scala3Test.scala:3:9
[error] 3 |  given x: Int = 1
[error]   |         ^
[error]   |         expression expected but : found
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] -- Error: ***/Scala3Test.scala:3:15 -----------
[error] 3 |  given x: Int = 1
[error]   |               ^
[error]   |               end of statement expected but '=' found
[error] -- [E018] Syntax Error: ***/Scala3Test.scala:7:16
[error] 7 |  given Ordering[Int] with
[error]   |                ^
[error]   |                expression expected but '[' found
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] -- [E006] Not Found Error: ***/Scala3Test.scala:3:2
[error] 3 |  given x: Int = 1
[error]   |  ^^^^^
[error]   |  Not found: given
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] -- Error: ***/Scala3Test.scala:5:3 ------------
[error] 5 |  f
[error]   |   ^
[error]   |No given instance of type Int was found for parameter x of method f in object Scala3Test
[error] -- [E006] Not Found Error: ***/Scala3Test.scala:7:2
[error] 7 |  given Ordering[Int] with
[error]   |  ^^^^^
[error]   |  Not found: given
[error]   |
[error]   | longer explanation available when compiling with `-explain`
[error] 6 errors found
[error] (Compile / compileIncremental) Compilation failed
[error] Total time: 3 s, completed 28 Sep 2022, 15:23:17

现在我禁用了-source:3.0-migration标志。

$ cat build.sbt
name := "scala-3-test"
scalaVersion := "3.2.0"
//scalacOptions += "-source:3.0-migration"
$ sbt compile
[info] compiling 1 Scala source to ***/target/scala-3.2.0/classes ...
[success] Total time: 3 s, completed 28 Sep 2022, 15:23:56

此外，编译器警告您注意Flag -source set repeatedly，即使您在构建文件中只设置了一次，这也意味着您也在其他地方设置了它。

如果您的项目中真的没有其他构建代码，包括可以设置一些您不知道的标志的插件，那么也许您的$HOME/.sbt/1.0文件夹中有一些允许插件或设置标志的代码。

Answer 2

移除

"-source:3.2-migration",

会有帮助的。