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Make Show inherit from a contravariant base trait #1649
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I wonder if we can get the test to pass by asking for
Show[_ >: A]
which is effectively what this trick is doing, and not having to introduce the new type. I think we can (at least on 2.12).There was a problem hiding this comment.
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Unfortunately type inference looks to be just slightly shy, like it was when I asked for
[A, B >: A](x: A)(implicit z: Show[B])
: it never converts anything to aShown
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when I did a simple test in the repl this worked when I did
implicitly[Foo[_ >: A]]
did you try that form (not putting a specific type)? you never know with scala which minor translation of the code will work.There was a problem hiding this comment.
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An implicit in the repl is like you've imported it. His is in the Shown companion object.
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right. That clarifies it for me.