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Allow using clauses to introduce Scala-2 conversions#13662

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odersky merged 1 commit intoscala:masterfromdotty-staging:fix-12955

Oct 4, 2021

Merged

Allow using clauses to introduce Scala-2 conversions#13662

odersky merged 1 commit intoscala:masterfromdotty-staging:fix-12955

Oct 4, 2021

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odersky commentedOct 3, 2021

Notably,(using A <:< B) should introduce an implicit conversion.
Previously that did not work since we tried to elaborate the context
parameter as ascala.Conversion.

Allow using clauses to introduce Scala-2 conversions

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Notably, `(using A <:< B)` should introduce an implicit conversion.Previously that did not work since we tried to elaborate the contextparameter as a `scala.Conversion`.

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Oct 3, 2021

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Scala 3 does not perform implicit conversion using <:<#12955

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odersky requested a review fromnicolasstucki

October 3, 2021 10:19

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Oct 3, 2021

dwijnand requested changes

Oct 4, 2021

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Unless I'm blind, this makes(using map: Map[String, Int]) a problem again. I think we should "just" special-case<:< (and thus its subclass=:=): I know it's a special-casing, but I see it as a retroactive definition of them as subclasses ofConversion. Perhaps it can even be special-cased that way: stickConversion as<:<'s base class or interfaces?

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odersky commentedOct 4, 2021

@dwijnand

Unless I'm blind, this makes (using map: Map[String, Int]) a problem again.

No, we do require that the implicit candidate returns aConversion for that test, whichMap does not do. There are actually two code points that are relevant here. One is infilterMatching where we do indeed special case<:<. The problem was that<:< can still only be used when passed as animplicit. And that's what is fixed by this PR.