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Merged
merged 16 commits into from
Sep 13, 2025
Merged

Disable distribution of intersection types over applied types #23441

merged 16 commits into from
Sep 13, 2025
+215 −102

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EugeneFlesselle
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@EugeneFlesselle EugeneFlesselle commented Jun 27, 2025 •
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Fixes soundness issue #23435

Note in particular that this implies we cannot (indirectly) inherit multiple instantiations of the same trait. E.g., see tests/neg/conflicting-inst-basetypes.scala.

The impact on the community-build appears to be rather reasonable, tweaks are required:

The changes should be relatively well regrouped by commit for review.

@EugeneFlesselle EugeneFlesselle force-pushed the distributeAnd branch 4 times, most recently from 2daa02b to 6171b84 Compare July 16, 2025 15:35
EugeneFlesselle added a commit to dotty-staging/dotty that referenced this pull request Jul 17, 2025
@EugeneFlesselle
Fix Lucre for scala#23441 change 2.3
49a906f
@EugeneFlesselle EugeneFlesselle marked this pull request as ready for review July 17, 2025 15:47
@EugeneFlesselle EugeneFlesselle linked an issue Jul 17, 2025 that may be closed by this pull request
Unsoundness with distribution of intersection over covariant types #23435
Closed
EugeneFlesselle added a commit to dotty-staging/dotty that referenced this pull request Jul 18, 2025
@EugeneFlesselle
Fix Lucre for scala#23441 change 2.3
a35f386
@EugeneFlesselle
Disable distribution of intersection types over applied types
9bb028d 
Fixes scala#23435
@EugeneFlesselle
Update zio community project
cba9856
@EugeneFlesselle
Update Lucre community project
114a1d2 
And add minimization
@EugeneFlesselle
Update parallel-collections community project
d0130ef
@EugeneFlesselle
Update specs2 community project
07b7571
@EugeneFlesselle
Update tests specifically about distributing intersections
e064a1c
@EugeneFlesselle
Update tests relating to inheritance of conflicting instantiations
942a747
@EugeneFlesselle
Disable TypeApplications#translateToRepeated distribution of AndTypes
9ee56c5
@EugeneFlesselle
Fix scala2-library-cc Sorted{Set,Map}FactoryDefaults self types
0441af0
@EugeneFlesselle
Adapt context-bound-companion logic to use AndType of AppliedTypes
a084779 
Instead of AppliedType of OrTypes, which relied on the distribution of AndTypes
when inheriting multiple context bound companions of the same name
@EugeneFlesselle
Update docs reference/spec of intersection/union types
73214ff
@EugeneFlesselle EugeneFlesselle requested a review from odersky July 18, 2025 15:28
@EugeneFlesselle EugeneFlesselle mentioned this pull request Jul 18, 2025
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odersky
odersky requested changes Sep 10, 2025
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To be conservative I'd make the main change in distributeAnd conditional on a source version or a -Y flag. That would give applications that critically rely on the unsoundness a way out.

@odersky odersky assigned EugeneFlesselle and unassigned odersky Sep 10, 2025
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odersky approved these changes Sep 13, 2025
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Looks good, thanks for squeezing these changes in your busy schedule!

@odersky odersky merged commit 85ca5d1 into scala:main Sep 13, 2025
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@odersky odersky deleted the distributeAnd branch September 13, 2025 08:40
@hamzaremmal hamzaremmal mentioned this pull request Sep 13, 2025
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hamzaremmal added a commit that referenced this pull request Sep 13, 2025
@hamzaremmal
Revert "Disable distribution of intersection types over applied types" (
afbb66b 
#23920)

Reverts #23441

We cannot compile the bootstrapped stdlib after this change. We will
investigate more during next week and remerge it with a fix for that
works with the stdlib too.
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Unsoundness with distribution of intersection over covariant types
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@EugeneFlesselle @odersky