Remove macro in FunctionK.lift implementation #2926
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This was referenced Jun 30, 2019
Instead, use the trick proposed by Alex in typelevel#2553 (comment), this is perhaps not ideal but it seems simpler than maintaining two separate source files for Scala 2 and Dotty, just for this one function. Additionally, since Dotty is able to call into non-macro methods in Scala 2 dependencies, this makes FunctionK.lift usable from Dotty without cats havin to publish Dotty artifacts. Co-authored-by: Alexander Konovalov <alex.knvl@gmail.com>
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Looks like there's no way to avoid at least regressing on type inference with any of the proposed approaches, so I think we'll have to go with split sources. |
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Just curious is the type inference regression also happens on 2.13? |
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Yup, same thing: error] /home/smarter/opt/cats/tests/src/test/scala/cats/tests/FunctionKSuite.scala:88:46: no type parameters for method lift: (f: F[cats.arrow.FunctionK.τ[F,G]] => G[cats.arrow.FunctionK.τ[F,G]])cats.arrow.FunctionK[F,G] exist so that it can be applied to arguments (Option[Nothing] => List[Nothing])
[error] --- because ---
[error] argument expression's type is not compatible with formal parameter type;
[error] found : Option[Nothing] => List[Nothing]
[error] required: ?F[cats.arrow.FunctionK.τ[?F,?G]] => ?G[cats.arrow.FunctionK.τ[?F,?G]]
[error] val fOptionToList = cats.arrow.FunctionK.lift(optionToList _)
[error] ^ |
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Instead, use the trick proposed by Alex in
#2553 (comment),
this is perhaps not ideal but it seems simpler than maintaining two
separate source files for Scala 2 and Dotty, just for this one function.
Additionally, since Dotty is able to call into non-macro methods in
Scala 2 dependencies, this makes FunctionK.lift usable from
Dotty without cats havin to publish Dotty artifacts.
Co-authored-by: Alexander Konovalov alex.knvl@gmail.com