odd community build failures after 2.12.9 re-STARR

[SethTisue]

in the 2.12 community build, after scala/community-build@7ef0adf:

-# July 31, 2019
-nightly=2.12.9-bin-87d43d0
+# August 5, 2019
+nightly=2.12.10-bin-f5b7822

two projects started having test failures (starting with https://scala-ci.typesafe.com/view/scala-2.12.x/job/scala-2.12.x-integrate-community-build/4800/)

one is scala-refactoring:

[scala-refactoring] [error] Test scala.tools.refactoring.tests.sourcegen.PrettyPrinterTest.testTypeDefs failed: expected:<...d type C >: Nothing [
[scala-refactoring] [error] 
[scala-refactoring] [error]   type D] <: AnyRef
[scala-refactoring] [error] }> but was:<...d type C >: Nothing [<: Any
[scala-refactoring] [error] 
[scala-refactoring] [error]   type D >: Nothing] <: AnyRef
[scala-refactoring] [error] }>

[scala-refactoring] [error] Test scala.tools.refactoring.tests.analysis.CompilationUnitDependenciesTest.importIsUsedAsTypeAscription210 failed: expected:<scala.[collection.immutable.Set
[scala-refactoring] [error] scala.this.Predef.Map
[scala-refactoring] [error] scala.this.Predef.any2ArrowAssoc]> but was:<scala.[Predef.ArrowAssoc
[scala-refactoring] [error] scala.Predef.Map
[scala-refactoring] [error] scala.collection.immutable.Set]>

and the other is zinc (an old-ish, frozen version of zinc, which may or may not be relevant):

[zinc] [info] ExtractUsedNamesSpecification:
[zinc] [info] Used names extraction
[zinc] [info] - should extract imported name
[zinc] [info] - should extract names in type tree
[zinc] [info] - should extract symbolic names
[zinc] [info] - should extract type names for objects depending on abstract types *** FAILED ***
[zinc] [info]   Set("A", "AnyRef", "Object", "scala", "java;lang;Object;init;") did not equal Set("A", "Nothing", "AnyRef", "Object", "scala", "java;lang;Object;init;", "Any") (ExtractUsedNamesSpecification.scala:84)

note that both repos' failures involve the absence or presence of a Nothing, which might be a clue that the root cause is somehow the same

[SethTisue]

in the Scala repo we have

% git hist 87d43d0..f5b7822
*   f5b7822a54 - Merge pull request #8312 from SethTisue/restarr-on-2.12.9 (3 days ago) <Seth Tisue>
|\  
| * 25aeea829a - re-STARR onto 2.12.9; begin 2.12.10-bin- series (3 days ago) <Seth Tisue>
|/  
*   d9db4d76c8 - Merge pull request #8291 from ashawley/rm-partest (3 days ago) <Seth Tisue>
|\  
| * 51c2beec55 - [nomerge] Remove accidental partest file backported to 2.12 (4 days ago) <Aaron S. Hawley>
* |   23b8068dfc - Merge pull request #8304 from diesalbla/replace_map2_with_foreach2_to_avoi_optimisations (3 days ago) <Diego E. Alonso Blas>
|\ \  
| * | 6cf10b0f1e - Replace map2 with foreach2. (6 days ago) <Diego E. Alonso-Blas>
|  /  
* |   c6c6c9485e - Merge pull request #8306 from diesalbla/Namers_reuse_typeParamsList (3 days ago) <Diego E. Alonso Blas>
|\ \  
| * | 3082f3abcd - Namers, PolyTypeCompleter: reuse the list of typeParams. (6 days ago) <Diego E. Alonso-Blas>
|  /  
* |   35580a03dc - Merge pull request #8305 from diesalbla/no_use_for_keyset (3 days ago) <Diego E. Alonso Blas>
|\ \  
| |/  
|/|   
| * b71ab2f08b - SpecialiseTypes: do not get a keyset. (6 days ago) <Diego E. Alonso-Blas>
* cca78e1e18 - (tag: v2.12.9) Merge pull request #8288 from ashawley/unmoored-comments (4 days ago) <Lukas Rytz>
* 72da647322 - Fix unmoored Scaladoc comments (8 days ago) <Aaron S. Hawley>

[SethTisue]

I can investigate further, bisect, etc. but I'll also ask: @retronym does this ring any bells with you?

[retronym]

@SethTisue Sorry, none of those changes appear suspicious to me.

[eed3si9n]

It might be a false positive / test bug for Zinc:

https://github.com/sbt/zinc/blob/4b414b66778399f044beccf749073b52e63bf5ef/internal/compiler-bridge-test/src/test/scala/sbt/internal/inc/ExtractUsedNamesSpecification.scala#L73-L74

    val versionDependentNames =
      if (scalaVersion.contains("2.10")) Set("Nothing", "Any") else Set()

Note that it's checking for Nothing only if scalaVersion contains "2.10". You know what contains "2.10"? 2.12.10-bin-f5b7822.

[SethTisue]

LOL. scala/community-build@7991c39

[SethTisue]

and I notice now that the scala-refactoring one is importIsUsedAsTypeAscription210, with suspicious 210

haha yeah @ScalaVersion(matches="2.10") and Properties.versionString().contains(onlyOn.matches()), it's the same

[SethTisue]

scala/community-build@e61ffa2