Fix #4771: Relax overriding check for polymorphic methods #4782
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odersky
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Jul 10, 2018
| // (Code like this is found in the collection strawman) | ||
| // | ||
| // 2. In the case of two method types or two polytypes with matching | ||
| // parameters and implicit status, merge corresppnding parameter |
| // 2. In the case of two method types or two polytypes with matching | ||
| // parameters and implicit status, merge corresppnding parameter | ||
| // and result types. | ||
| (tp1, tp2) match { |
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This is bound to be very inefficient since we do not optimize tupled pattern matches yet. I suggest to use nested matches instead, similar to how it is done in infoJoin.
| if ctx.typeComparer.matchingPolyParams(tp1, tp2) => | ||
| tp1.derivedLambdaType( | ||
| mergeParamNames(tp1, tp2), | ||
| (tp1.paramInfos, tp2.paramInfos).zipped |
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Shorter and more efficient: use zipWithConserve (in Decorators.scala)
| if ctx.typeComparer.matchingPolyParams(tp1, tp2) => | ||
| tp1.derivedLambdaType( | ||
| mergeParamNames(tp1, tp2), | ||
| (tp1.paramInfos, tp2.paramInfos).zipped |
Just like in Scala 2, we now allow an override to widen the bounds of a polymorphic type parameter (this is sound because parameters can vary contravariantly). (And just like Scala 2, we continue not allowing an overriding to widen the type of a term parameter).
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Just like in Scala 2, we now allow an override to widen the bounds of a
polymorphic type parameter (this is sound because parameters can vary
contravariantly). (And just like Scala 2, we continue not allowing an
overriding to widen the type of a term parameter).