Properly handle SAM types with wildcards #18201
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Will this be backport to 3.3.x? |
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Previously there were two separate checks for contextual function types as result types: one in SAMType for non-PartialFunctions and one in ExpandSAM for PartialFunctions. This is replaced by a single check (with a detailed error message like we already had for PartialFunctions).
When typing a closure with an expected type containing a wildcard, the closure type itself should not contain wildcards, because it might be expanded to an anonymous class extending the closure type (this happens on non-JVM backends as well as on the JVM itself in situations where a SAM trait does not compile down to a SAM interface). We were already approximating wildcards in the method type returned by the SAMType extractor, but to fix this issue we had to change the extractor to perform the approximation on the expected type itself to generate a valid parent type. The SAMType extractor now returns both the approximated parent type and the type of the method itself. The wildcard approximation analysis relies on a new `VarianceMap` opaque type extracted from Inferencing#variances. Fixes scala#16065. Fixes scala#18096.
dwijnand
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This was dropped in scala#18201 which restricted SAM types to valid parent types, but it turns out that there is code in the wild that relies on refinements being allowed here. To support this properly, we had to enhance ExpandSAMs to move refinements into type members to pass Ycheck (previous Scala 3 releases would accept the code in tests/run/i18315.scala but fail Ycheck). Fixes scala#18315.
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This was dropped in scala#18201 which restricted SAM types to valid parent types, but it turns out that there is code in the wild that relies on refinements being allowed here. To support this properly, we had to enhance ExpandSAMs to move refinements into type members to pass Ycheck (previous Scala 3 releases would accept the code in tests/run/i18315.scala but fail Ycheck). Fixes scala#18315.
smarter
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This was dropped in #18201 which restricted SAM types to valid parent types, but it turns out that there is code in the wild that relies on refinements being allowed here. To support this properly, we had to enhance ExpandSAMs to move refinements into type members to pass Ycheck (previous Scala 3 releases would accept the code in tests/run/i18315.scala but fail Ycheck). Fixes #18315. This should be backported to any branch where #18201 is backported.
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Backports #18201 to the LTS branch. PR submitted by the release tooling.
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This was dropped in scala#18201 which restricted SAM types to valid parent types, but it turns out that there is code in the wild that relies on refinements being allowed here. To support this properly, we had to enhance ExpandSAMs to move refinements into type members to pass Ycheck (previous Scala 3 releases would accept the code in tests/run/i18315.scala but fail Ycheck). Fixes scala#18315.
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When typing a closure with an expected type containing a wildcard, the closure
type itself should not contain wildcards, because it might be expanded to an
anonymous class extending the closure type (this happens on non-JVM backends as
well as on the JVM itself in situations where a SAM trait does not compile down
to a SAM interface).
We were already approximating wildcards in the method type returned by the
SAMType extractor, but to fix this issue we had to change the extractor to
perform the approximation on the expected type itself to generate a valid
parent type. The SAMType extractor now returns both the approximated parent
type and the type of the method itself.
The wildcard approximation analysis relies on a new
VarianceMapopaque typeextracted from Inferencing#variances.
Fixes #16065.
Fixes #18096.