Changes to wildApprox #1054
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Changes to wildApprox #1054
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See comment in new overloaded variant of wildApprox for an explanation. Fixes scala#1044. Review by @smarter.
| @@ -379,6 +379,19 @@ object ProtoTypes { | |||
| } | |||
| } | |||
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| /** Like wildApprox, but assume that all parameters of `disregarded` are not | |||
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It's a bit weird to say "Like wildApprox" when this method is called wildApprox too, maybe use another name, or say, "Like the other overload of wildApprox"?
smarter
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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.
smarter
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Feb 5, 2016
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 have an alternative fix which I think is a cleaner solution: #1056 |
smarter
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When `wildApprox` encounters a PolyParam it approximates it by its bounds in the current constraint set, but this is incorrect if `TypevarsMissContext` is set, we might get the bounds of another use of this `PolyType`. This is exactly what happened in i1044.scala where the implicit view `refArrayOps` needs to be used twice with two different type parameters. The fix is to approximate a PolyParam by its original bounds in its PolyType if `TypevarsMissContext` is set. This fix was inspired by the approach of scala#1054.
smarter
added a commit
to dotty-staging/dotty
that referenced
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Feb 6, 2016
When `wildApprox` encounters a PolyParam it approximates it by its bounds in the current constraint set, but this is incorrect if `TypevarsMissContext` is set, we might get the bounds of another use of this `PolyType`. This is exactly what happened in i1044.scala where the implicit view `refArrayOps` needs to be used twice with two different type parameters. The fix is to approximate a PolyParam by its original bounds in its PolyType if `TypevarsMissContext` is set. This fix was inspired by the approach of scala#1054.
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Superceded by #1064 |
OlivierBlanvillain
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Dec 8, 2016
OlivierBlanvillain
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See comment in new overloaded variant of wildApprox for an explanation.
Fixes #1044.
Review by @smarter.