Closed
Description
Compiler version
Scala code runner version 3.1.2-RC1-bin-SNAPSHOT-git-0f6d16e -- Copyright 2002-2021, LAMP/EPFL (newest)
Minimized code
import scala.quoted.*
import scala.tasty.inspector.*
class Test:
List() match
case Nil => 1
case _ :: tail => 2
class I extends Inspector:
override def inspect(using q: Quotes)(tastys: List[Tasty[quotes.type]]): Unit =
import q.reflect.*
val tree: Tree = tastys(0).ast
val traverser = new TreeTraverser {}
traverser.traverseTree(tree)(tree.symbol)
object Main extends App:
TastyInspector.inspectAllTastyFiles(List("here/Test.tasty"), Nil, Nil)(new I)
Simply copy it into bug.scala and run
mkdir here
bin/scalac -d here bug.scala && bin/scala bug.scala
Output
scala.MatchError: Typed(UnApply(TypeApply(Select(Ident(::),unapply),List(TypeTree[TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),Nothing)])),List(),List(Ident(_), Bind(tail,Ident(_)))),TypeTree[AppliedType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class collection)),object immutable),::),List(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),Nothing)))]) (of class dotty.tools.dotc.ast.Trees$Typed)
at scala.quoted.Quotes$reflectModule$TreeAccumulator.foldOverTree(Quotes.scala:4427)
at scala.quoted.Quotes$reflectModule$TreeAccumulator.foldOverTree$(Quotes.scala:4340)
at I$$anon$1.foldOverTree(bug.scala:13)
at scala.quoted.Quotes$reflectModule$TreeTraverser.traverseTreeChildren(Quotes.scala:4449)
at scala.quoted.Quotes$reflectModule$TreeTraverser.traverseTreeChildren$(Quotes.scala:4443)
at I$$anon$1.traverseTreeChildren(bug.scala:13)
...Expectation
Completes without error
This code was working good in 3.1.0-RC1 and stopped working in 3.1.0. My guess is that the problem comes from match here:
https://github.com/lampepfl/dotty/blob/master/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala#L344
UnApply is subtype tpd.PatternTree which returns None. I claim so, because I have encountered some Typed(...) that were not causing problem with traversing, but all of them returned Some(...) from this function.