Here's an error that I got spuriously but rerunning the compilation made it go away.
[E] [E1] config/src/main/scala-2.11-13/bloop/config/ConfigCodecs.scala:119:42
[E] Cannot evaluate a parameter of the 'make' macro call for type 'bloop.config.Config.JvmConfig'. It should not depend on code from the same compilation module where the 'make' macro is called. Use a separated submodule of the project to compile all such dependencies before their usage for generation of codecs. Cause:
[E] java.lang.AssertionError: assertion failed: pkgClass = package <root>, sym = package com, existing = package com (depth=0)
[E] L119: JsonCodecMaker.make[Config.JvmConfig](CodecMakerConfig.withTransientEmpty(false))
[E] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[E] config/src/main/scala-2.11-13/bloop/config/ConfigCodecs.scala: L119 [E1]