ZIO Does Not Compile Against Latest Nightly Version of Dotty

[adamgfraser]

Following up discussion in zio/zio#2412 we are not able to compile ZIO against the latest nightly version of Dotty. We are testing all PRs against Dotty 0.20 as part of our CI process so it appears that the issue relates to a change since then. Specifically, I am getting the following error:

[error] not found: /drone/src/library/src/scala/internal/Quoted.scala
[error] not found: /drone/src/library/src/scala/internal/Quoted.scala
[error] not found: /drone/src/library/src/scala/internal/Quoted.scala
[error] not found: /drone/src/library/src/scala/quoted/QuoteContext.scala
[error] not found: /drone/src/library/src/scala/quoted/QuoteContext.scala
[error] not found: /drone/src/library/src/scala/quoted/QuoteContext.scala

To reproduce, you can change this line in ZIO to use the latest Dotty nightly and then attempt to compile after setting the version to Dotty or do the same thing with my local branch here.

Sorry I don't have a more detailed diagnosis. Copying @smarter and @neko-kai.

[nicolasstucki]

@adamgfraser which sbt commands should I use to reproduce it?

[adamgfraser]

@nicolasstucki See below.

./sbt
++ 0.21.0-bin-20191202-ccb7b13-NIGHTLY
project stacktracerJVM
compile

[nicolasstucki]

If I publish the latest version of dotty locally it works. Maybe something is missing when publishing the artifacts. In which case 9e4ee9f looks like a likely suspect.

[smarter]

If I publish the latest version of dotty locally it works

If you publish it locally then the path to Quoted.scala will be a real file on your filesystem, so it makes sense that it would work and not emit a "not found" error.

[nicolasstucki]

true

[nicolasstucki]

I bisected it and it started in 59ea176

[nicolasstucki]

@smarter could you have a look? Revering 59ea176 fixes the issue

[smarter]

That looks completely unrelated, no idea.

[nicolasstucki]

Double-checking it I saw that reverting it did not help

[nicolasstucki]

It is actually 7185680

[nicolasstucki]

@adamgfraser could you try to minimize it in a self-contained example? Debugging this on the full ZIO project will be too complex and will not allow us to add a good regression test.

[bishabosha]

so if you unzip the jar file for the artifact ch.epfl.lamp:dotty-library_0.21-0.21.0-bin-20191202-ccb7b13-NIGHTLY, these strings can be found in the raw tasty files scala/quoted/QuoteContext.tasty and scala/internal/Quoted.tasty, but not in the contents if you do -print-tasty or -decompile on them

[smarter]

The error comes from this check: https://github.com/lampepfl/dotty/blob/0a33ad34e212d3eba2ecd41fac07dddc172e149d/compiler/src/dotty/tools/dotc/CompilationUnit.scala#L92-L95 which I don't think is actually useful.

[adamgfraser]

Yes. I was trying to minimize the example, at one point got a version with code commented out that compiled, and now I am able to compile the entire project successfully with no code commented out. So it seems like maybe there is some check for a missing file that is occurring too early, so we're not getting to the point where that file can be generated?

[adamgfraser]

Thank you!