StreamConverters.toScala in 2.12-style

[lrytz]

Fixes #144

[lrytz]

Review by @dwijnand - you had a case that was affected, no?

[dwijnand]

Yes, scalacommunitybuild/playframework@2607f07.

Visually comparing a few things this looks to resolve that issue. So LGTM.

[dwijnand]

In comparing the test case in 2.13.x with the one in master there are a few changes, particularly these kinds of ones:

-      assertEq(vecO, newStream(n).accumulate.to[Vector], s"stream $n to vector")
-      assertEq(vecO, accO.to[Vector], s"stream $n to vector in parallel")
+      assertEq(vecO, newStream(n).accumulate.to(Vector), s"stream $n to vector")
+      assertEq(vecO, accO.to(Vector), s"stream $n to vector in parallel")

See master...lrytz:toScalaTypeParam#diff-fb9126fd878d17950f0dbccaed6d630c.

[lrytz]

Thanks for checking. The problem here is that the Accumulator type, when using scala-java8-compat on 2.13, is the one from the 2.13 standard library. So its .to method has the new 2.13 shape, it takes a (non-implicit) factory value parameter.

I'm not sure how we could bridge that gap here, i.e., I don't see a way to make the accumulator.to[Vector] syntax work when using scala-java8-compat on 2.13. However, one could use scala-collection-compat to make the accumulator.to(Vector) syntax work when using scala-java8-compat on 2.12. (scala-collection-compat doesn't add a new to extension method for that, but instead provides implicit conversions from collection companions to CanBuildFrom instances, so that the 2.12 to method can be used in the 2.13 style).