Changing class parameters doesnt recompile dependent code

[sake92]

steps

• clone https://github.com/sake92/metals-mill-scala3-class-params-repro
• open with VSCode+Metals
• import as Mill build (Bloop or mill-bsp)
• run, all good
• add parameter to MyService
• Hello still compiles but should not compile

problem

Hello still compiles.

expectation

Hello should not compile.

notes

Seems to be scala 3 related. It works with 2.13 for example

Original issue in Metals: https://github.com/scalameta/metals/issues/6112

[SethTisue]

fyi @Gedochao, as the root cause may be in the Dotty repo

[sake92]

Hmm, I noticed another similar issue..
I moved a class to another folder, even changed the package, and it did not fail compilation.. Really weird

[sake92]

It's not a Mill issue btw, I've added sbt too, same issue.
What I didn't realize at the time is that the code successfully compiles, but throws NoSuchMethodError !

PS C:\projects\sake\metals-mill-scala3-class-params-repro> mill scalaHelloWorld.run
[36/49] scalaHelloWorld.compile
[info] compiling 1 Scala source to C:\projects\sake\metals-mill-scala3-class-params-repro\out\scalaHelloWorld\compile.dest\classes ...
[info] done compiling
[49/49] scalaHelloWorld.run
Exception in thread "main" java.lang.NoSuchMethodError: 'void example.MyService.<init>(java.lang.String)'
        at example.Hello$.<clinit>(Hello.scala:5)
        at example.Hello.main(Hello.scala)
1 targets failed
scalaHelloWorld.run subprocess failed

[eed3si9n]

@sake92 Would something like the following be an example?

class MyService(str: String, i: Int)

Like Seth suggested, likely this is more to do with the compiler bridge issue, and not specific to the build tools that calls into Zinc like Mill or sbt.

[eed3si9n]

val service = MyService("fssdfs")

My guess is that the new new-less syntax is failing to register dependency relationship to the MyService constructor, so when the constructor changed, Hello object isn't recompiled.

[eed3si9n]

Actually adding new didn't change the behavior:

> hello/run
[info] compiling 1 Scala source to /private/tmp/metals-mill-scala3-class-params-repro/scalaHelloWorld/target/scala-3.3.1/classes ...
[info] running example.Hello
Exception in thread "sbt-bg-threads-13" java.lang.NoSuchMethodError: 'void example.MyService.<init>(java.lang.String)'
    at example.Hello$.<clinit>(Hello.scala:5)
    at example.Hello.main(Hello.scala)

[eed3si9n]

I suggest reporting this to https://github.com/scala/scala3/issues.

[sake92]

Thanks for checking @eed3si9n .
I'll report to the scala3 repo.