Alternative fix for #1044: Properly constrain polymorphic implicit views #1056
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When `wildApprox` encounters a PolyParam it approximates it by its bounds in the current constraint set, this only makes sense if we have added the PolyType corresponding to this PolyParam to the constrain set using `ProtoTypes#constrained`, otherwise, we might get the bounds of another use of this `PolyType`. This is exactly what happened in i1044.scala: to compile, the implicit view `refArrayOps` needs to be used twice with two different type parameters. The fix is to always constrain polymorphic implicit views before calling `wildApprox` on their result type. This fix was inspired by the approach of scala#1054.
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I now think that we don't need to call |
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Review by @odersky, this is an alternative to #1054
When
wildApproxencounters a PolyParam it approximates it by itsbounds in the current constraint set, this only makes sense if we have
added the PolyType corresponding to this PolyParam to the constrain set
using
ProtoTypes#constrained, otherwise, we might get the bounds ofanother use of this
PolyType. This is exactly what happened ini1044.scala: to compile, the implicit view
refArrayOpsneeds to beused twice with two different type parameters.
The fix is to always constrain polymorphic implicit views before
calling
wildApproxon their result type.This fix was inspired by the approach of #1054.