Avoid loosing denotations of named types during integrate
#22839
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…`TypeMap`s" This reverts commit bb63e31.
This was referenced Mar 31, 2025
mbovel
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this pull request
Apr 1, 2025
Fixes #22874. `wildApprox` approximates parameter references and type variables by wildcards. When doing so for an `AnnotatedType`, this can produce trees with wildcards types, causing the type assigner to fail. For example, consider `Apply(fn, args)` where `fn` has type `TermParamRef`. Applying `wildApprox` will approximate the type of `fn` to a wildcard, leading [the type assigner for `Apply`](https://github.com/scala/scala3/blob/cb97c40930d335e0fca38238682d218c3e718bd8/compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala#L298) to emit an error stating that `<?>` does not take parameters. This issue is somehow similar to the one described in #19957 (comment), which was fixed by #21941 (and re-worked in #22839). This PR fixes the issue by approximating annotated types in `wildApprox`: annotated types are approximated by their parent types if they are not refining, or by wildcards upper-bounded by their parent types if they are.
odersky
requested changes
Apr 6, 2025
| private class IntegrateMap(params: List[Symbol], paramRefs: List[Type])(using Context) extends TypeMap: | ||
| override def apply(tp: Type) = | ||
| tp match | ||
| case tp: NamedType if params.contains(tp.symbol) => paramRefs(params.indexOf(tp.symbol)) |
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This is duplicates code from SubstMap, but at lower performance. I think we should factor out only what is essential here:
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Make Substituters.SubstMap non-final and note that it is overridden by IntergrateMap in the comment.
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Define IntegrateMap as
private class IntegrateMap(params: List[Symbol], paramRefs: List[Type])(using Context) extends Substituters.SubstMap(params, paramrefs): override def derivedSelect(tp: NamedType, pre: Type): Type = ...
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