fix: support variance for type parameters of opaque types in Scala 3 (Issue #548)#578
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Erichhhhhcat wants to merge 1 commit intozio:developfrom
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fix: support variance for type parameters of opaque types in Scala 3 (Issue #548)#578Erichhhhhcat wants to merge 1 commit intozio:developfrom
Erichhhhhcat wants to merge 1 commit intozio:developfrom
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Fixes issue zio#548 - Scala 3: support variance reading for opaque types For opaque type aliases, declaredTypes returns an empty list because the type parameters are not 'declared' in the traditional sense. This fix adds a fallback to use typeSymbol.typeParams to extract variance information for opaque types.
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@Erichhhhhcat Hi, thanks for your contribution! 🙏 Could you please add a test case to scala-3 specific LightTypeTagTest.scala demonstrating the fix? |
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Feb 24, 2026
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Summary
Fixes issue #548 - Scala 3: support variance reading for opaque types
Problem
For opaque type aliases in Scala 3,
declaredTypesreturns an empty list because the type parameters are not 'declared' in the traditional sense. This caused variance detection to fail:Solution
Added a fallback to use
typeSymbol.typeParamsto extract variance information whendeclaredTypesis empty and the symbol is an opaque alias.Testing
This fix enables correct variance detection for opaque types in Scala 3.