Avoid forcing whole package when using -experimental
#20409
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In scala#19807, the behavior of `-experimental` was changed to mark all top-level definitions as experimental. To do so, the implementation traverses the whole package and checks every symbol to see if it should be transformed or not. The problem was that the first check we do is `sym.isExperimental` which ends up forcing the symbol. Besides being a performance issue, this could also lead to a crash if the current package is the empty package, because we could end up forcing the magic `module-info.class` that Java modules place there. For some reason, this appear to only happen when building with sbt, hence the additional scripted test. This PR fixes this issue by reordering the checks (and adding a preliminary `isDefinedInCurrentRun` check for good measure). We should also investigate whether we can avoid creating a symbol for `module-info.class`, but this PR is intentionally minimal so we can backport it to 3.5.0-RC2 without risks.
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odersky
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May 16, 2024
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Don't know if it is related (as hinted by @som-snytt ) but here is a crash in REPL when loading class module-info that also for some reason only happens in sbt: |
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@bjornregnell Could you open a separate issue for this? We should address the root cause here but I'd like to get this in first. |
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May 16, 2024
This backports scala#20409 which fixes a regression introduced in 3.5.0-RC1 causing compiler crashes when enabling `-experimental`.
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Other issue now cross-posted here: #20421 |
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In #19807, the behavior of
-experimentalwas changed to mark all top-level definitions as experimental. To do so, the implementation traverses the whole package and checks every symbol to see if it should be transformed or not. The problem was that the first check we do issym.isExperimentalwhich ends up forcing the symbol.Besides being a performance issue, this could also lead to a crash if the current package is the empty package, because we could end up forcing the magic
module-info.classthat Java modules place there. For some reason, this appear to only happen when building with sbt, hence the additional scripted test.This PR fixes this issue by reordering the checks (and adding a preliminary
isDefinedInCurrentRuncheck for good measure). We should also investigate whether we can avoid creating a symbol formodule-info.class, but this PR is intentionally minimal so we can backport it to 3.5.0-RC2 without risks.