Scala 3 / Dotty Support

[ekrich]

Blockers

This issue is a overall issue to keep track of Dotty support. Different PRs are being worked on and merged to master as long as the changes are backward compatible.

• Dotty backend does not generate serialVersionUID Dotty backend does not generate serialVersionUID scala/scala3#7319

Fix was merged in 0.20.0-RC1 so we have serialization but the output is not the same.

• Investigate serialization difference. These seem to be caused by the inability to assign an Enum to a value running into the following Bad type operand on stack errors or the like.

Blocked on the following issues.

• This is the closest issue - Compiling code with Enums in without doing a clean compile causes runtime VerifyError scala/scala3#6664 which is part of this issue.
• Enum Improvements Epic Enum Improvements Epic scala/scala3#7501
• Maybe this is the issue? Singleton enum cases (marked Serializable) are incorrectly serialized scala/scala3#9179

Update: 9-2-2020 - Dotty 0.27.0-RC1 - One test fails - org.ekrich.config.impl.ValidationTest.validationFailedSerializable
Error: java.io.NotSerializableException: org.ekrich.config.impl.SimpleConfigOrigin
Ignored for now - needs investigating.

• Found the issue - Serialization fails when @transient val is passed to constructor scala/scala3#9881

This is currently not passing the tests due to a Callable[Config] that produces a value correctly but does not get assigned correctly. This call returns a config - https://github.com/ekrich/sconfig/blob/topic/dotty2/sconfig/shared/src/main/scala/org/ekrich/config/impl/ConfigImpl.scala#L54 when debugged from here - https://github.com/ekrich/sconfig/blob/topic/dotty2/sconfig/shared/src/main/scala/org/ekrich/config/impl/ConfigImpl.scala#L353-L365 - but then always falls through to this code - https://github.com/ekrich/sconfig/blob/topic/dotty2/sconfig/shared/src/main/scala/org/ekrich/config/impl/ConfigImpl.scala#L65-L66

The above has been reported and considered.

• Miscompilation: When a try expression mutating a var is lifted, incorrect code is generated Miscompilation: When a try expression mutating a var is lifted, incorrect code is generated scala/scala3#7356

This code now has been modified to avoid this problem so the code will work and test. See 2ae7d88

Java Blockers

These are lower priority as Java can use the Java API but these keep all the functionality from working.

• Do not autoimport scala.* when parsing .java files Do not autoimport scala.* when parsing .java files scala/scala3#7312 Fixed as of 0.27.0-bin-20200810-74ba21c-NIGHTLY
• @vararg annotation when called from Java does not compile @vararg annotation when called from Java does not compile scala/scala3#7212

[ekrich]

First PR. #48

[ekrich]

Second PR. #49

[ekrich]

Third and fourth: #62 and #65
Modified the build so a subset of the tests will compile. Include fixes for non-local returns which removes the warnings.

[ekrich]

Vararg will be fixed on the next release of Dotty. See #85

[ekrich]

This issue scala/scala3#7312 is now fixed so the Java files need to be reverted. Fix check mark above when completed.
The 20200810 nightly or later can be tested.

[ekrich]

There is one serialization test failing now based on changes in this PR - #92

Once this has been fixed and the pull merged, this issue can be closed.