SAM type change causes undercompilation

[eed3si9n]

This is yet another example of Zinc lagging Scala language spec change.
https://www.scala-lang.org/news/2.12.0/#lambda-syntax-for-sam-types

steps

Haven't minimized it but I noticed while coding. First you have a Java interface in one subproject.

import java.nio.file.Path;
import java.util.Optional;

public interface SingleOutput {
    public Path getOutputDirectory();

    public default Optional<Path> getSingleOutput() {
        return Optional.of(getOutputDirectory());
    }
}

In another subproject, use it as SAM-type lambda:

val output: SingleOutput = () => RootFilePath.resolve("out")

Then change the Java interface..

import java.io.File;
import java.util.Optional;

public interface SingleOutput {
    public File getOutputDirectory();

    public default Optional< File > getSingleOutput() {
        return Optional.of(getOutputDirectory());
    }
}

problem

The Scala code is not invalidated. So locally compile keeps succeeding. On CI the build fails if it's compiled from scratch.

expectation

Invalidate correctly.

[smarter]

Fixed in Scala 3 with scala/scala3#16996.

[smarter]

Interesting, this got closed from a commit in another repo, but should be kept open since it's still an issue in scala 2.