Mirror.SumOf fails to summon in the context of multiple files

[anatoliykmetyuk]

Test.scala:

def Test =
  summon[deriving.Mirror.SumOf[Foo]]

Wrapper.scala:

sealed trait Foo
case class Bar(x: Int) extends Foo

Compile together while specifying Test.scala first in the compiler command: dotty-bootstrapped/dotc -d out Test.scala Wrapper.scala.

Output:

-- Error: /Users/kmetiuk/Projects/scala3/playground/upickle-pg/Test.scala:2:36 -
2 |  summon[deriving.Mirror.SumOf[Foo]]
  |                                    ^
  |no implicit argument of type deriving.Mirror.SumOf[Foo] was found for parameter x of method summon in object DottyPredef
-- Error: /Users/kmetiuk/Projects/scala3/playground/upickle-pg/Wrapper.scala:2:11
2 |case class Bar(x: Int) extends Foo
  |           ^
  |children of trait Foo were already queried before class Bar was discovered.
  |As a remedy, you could move class Bar on the same nesting level as trait Foo.
2 errors found

If you flip the order of the files in the command (dotty-bootstrapped/dotc -d out Wrapper.scala Test.scala) or compile them as a single file:

sealed trait Foo
case class Bar(x: Int) extends Foo
def Test =
  summon[deriving.Mirror.SumOf[Foo]]

The compilation succeeds.

You can reproduce the issue with Dotty Issues Workspace using the following launch.iss script:

launch.iss

$ (rm -rv out || true) && mkdir out  # Cleanup

dotty-bootstrapped/dotc -d out
  $here/Test.scala $here/Wrapper.scala

/cc @milessabin

[smarter]

Same issue as #9064 ?

[anatoliykmetyuk]

Could be. I discovered it in upickle, and it also kept blowing up with java.lang.OutOfMemoryError.