Build breakages involving scala-cc-library

[odersky]

Compiler version

3.4.0

Minimized example

Change an item in stdlibPatches/Predef.scala.

In fact, it seems any change to a source in library/ will trigger the same problem.

Output

The build breaks with errors when trying to re-build scala-library-cc.

sbt:scala3> scala3-bootstrapped/testCompilation
[info] compiling 46 Scala sources to /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes ...
[info] compiling 45 Scala sources to /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-bootstrapped/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes ...
[error] -- [E008] Not Found Error: /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/src_managed/main/scala-library-src/scala/Enumeration.scala:100:23 
[error] 100 |    ((getClass.getName stripSuffix MODULE_SUFFIX_STRING split '.').last split
[error]     |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |value stripSuffix is not a member of ... (cannot display due to UnpicklingError Could not read definition type Stream in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/package.tasty. Caused by the following exception:
[error]     |dotty.tools.dotc.core.UnpicklingError: Could not read definition trait SeqOps in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/collection/SeqOps.tasty. Caused by the following exception:
[error]     |dotty.tools.dotc.core.UnpicklingError: Could not read definition trait SeqViewOps in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/collection/SeqViewOps.tasty. Caused by the following exception:
[error]     |dotty.tools.dotc.core.CyclicReference: Cyclic reference involving trait Seq
[error]     |
[error]     |Run with -Ydebug-unpickling to see full stack trace.) ....
[error]     |Extension methods were tried, but the search failed with:
[error]     |
[error]     |    Could not read definition method tuple3ToZippedOps in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/Predef.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.UnpicklingError: Could not read definition object Tuple3Zipped in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/runtime/Tuple3Zipped.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.UnpicklingError: Could not read definition class Tuple3Zipped in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/runtime/Tuple3Zipped.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.UnpicklingError: Could not read definition type Iterable in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/package.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.UnpicklingError: Could not read definition trait Iterable in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/collection/Iterable.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.UnpicklingError: Could not read definition trait Iterable in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/collection/immutable/Iterable.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.UnpicklingError: Could not read definition trait IterableOps in /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/classes/scala/collection/IterableOps.tasty. Caused by the following exception:
[error]     |    dotty.tools.dotc.core.CyclicReference: Cyclic reference involving trait Seq
[error]     |    
[error]     |    Run with -Ydebug-unpickling to see full stack trace.
[error] -- [E046] Cyclic Error: /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/src_managed/main/scala-library-src/scala/Enumeration.scala:119:43 
[error] 119 |      vset = (ValueSet.newBuilder ++= vmap.values).result()
[error]     |                                           ^
[error]     |                   Cyclic reference involving method tuple3ToZippedOps
[error]     |
[error]     | longer explanation available when compiling with `-explain`
[error] -- Error: /Users/odersky/workspace/dotty/out/bootstrap/scala2-library-cc/scala-3.4.0-RC1-bin-SNAPSHOT-nonbootstrapped/src_managed/main/scala-library-src/scala/Enumeration.scala:148:35 
[error] 148 |  final def apply(x: Int): Value = vmap(x)
[error]     |                                   ^
[error]     |Recursion limit exceeded.
[error]     |Maybe there is an illegal cyclic reference?
[error]     |If that's not the case, you could also try to increase the stacksize using the -Xss JVM option.
[error]     |For the unprocessed stack trace, compile with -Yno-decode-stacktraces.
[error]     |A recurring operation is (inner to outer):
[error]     |
[error]     |  subtype CC[X0, X1] <:< CC[X0, X1]
[error]     |  subtype CC[X0, X1] <:< CC[X0, X1]
[error]     |  subtype CC[X0, X1] <:< CC[X0, X1]
[error]     |  subtype CC[X0, X1] <:< CC[X0, X1]

and lots of errors after that.

Expectation

If scala-cc-library needs to rebuild, the build script should force a clean build, since that's required to build it correctly.

[odersky]

This problem makes working with dotty almost impossible. Whenever I switch branches I get a build breakage with scala-cc-library. So either we don't update scala-cc-library not at all automatically, or we build it correctly.