2.13: compatibility with new name-based extractor scheme #253
Comments
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(sorting this out is a blocker for releasing 2.13.0-M5) |
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Right, if the community build is using the newCollectionsBootstrap branch from #222, then it should be compiling still for 2.13.0-M4. We hardcoded Is there a test somewhere in the compiler to verify pattern matching with |
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I think the part of scala/scala#7068 that's causing the problem is "This PR changes the type of |
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I'll try this in the community build: scalacommunitybuild/scala-xml@5f67a6f |
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Here are the definitions of Elem.unapplySeq(n: Node): Option[(String, String, MetaData, NamespaceBinding, Seq[Node])]
Node.unapplySeq(n: Node): Some[(String, MetaData, Seq[Node])]
QNode.unapplySeq(n: Node): Some[(String, String, MetaData, Seq[Node])]And adding |
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Guess we'll see! |
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as far as I can see that would cross-compile, yes. but, perhaps there's a more efficient solution if we're concerned about avoiding unnecessary copying? would need a little thought/investigation |
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I've tried to write a minimal partest that replicates the import scala.collection.AbstractSeq
import scala.collection.SeqOps
import scala.collection.immutable.StrictOptimizedSeqOps
abstract class CollectionSeq
extends AbstractSeq[Int]
with scala.collection.Seq[Int]
with SeqOps[Int, scala.collection.immutable.Seq, CollectionSeq]
with StrictOptimizedSeqOps[Int, scala.collection.immutable.Seq, CollectionSeq]
{
def first: Int
def more: scala.collection.Seq[CollectionSeq]
def iterator: Iterator[Int] = ???
def apply(i: Int): Int = ???
def length: Int = ???
}
case class CollSeqCons(first: Int, more: CollectionSeq*) extends CollectionSeq
object CollectionSeq {
def unapplySeq(x: CollectionSeq) = Some((x.first, x.more))
}
object Test extends App {
def f(x: CollectionSeq): CollectionSeq = x match {
case CollSeqCons(x, xs @ _*) => CollSeqCons(x, xs: _*)
}
} |
attn @lrytz |
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I looked into this issue, I didn't see anything unexpected. We should improve the error message though for RC1, as the change breaks existing Here's a self-contained reproduction: abstract class Node extends NodeSeq {
def label: String
def child: scala.collection.Seq[Node]
}
object Elem {
def unapplySeq(n: Node): Option[(String, collection.Seq[Node])] = Some((n.label, n.child))
}
abstract class NodeSeq extends collection.immutable.Seq[Node] {
def theSeq: collection.Seq[Node]
def length = theSeq.length
def iterator = theSeq.iterator
def apply(i: Int): Node = theSeq(i)
}
object NodeSeq {
import scala.language.implicitConversions
implicit def seqToNodeSeq(s: collection.Seq[Node]): NodeSeq = new NodeSeq {
def theSeq = s
}
}
object Test {
def foo(n: Node) = n match {
case Elem(label, child @ _*) => child
}
}The error message is because the binding This fails to type-check and produces the error message ( Note that it's enough to change |
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Did adding I tried compiling on the latest M5 with Seth's branch: When I look in the last passing 2.13 community build from Aug-22 I only see scala-xml getting skipped: Hopefully, I'm using the right M5: |
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I believe this got fixed in 2.13.0-M5 by scala/scala#7120. I'm having a hard time remembering. |
after scala/scala#7068 was merged, in the 2.13 community build (https://scala-ci.typesafe.com/job/scala-2.13.x-integrate-community-build/1371/consoleFull) we have:
and a few more such errors.
does this indicate that there is code in scala-xml that needs to be adjusted to the new scheme for name-based extractors? or is there a flaw in scala/scala#7068?
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