assertion failed: position not set for dotty.tools.dotc.core.Decorators.className(<empty>) in dotty

[KacperFKorban]

1. In scala/scala3 repo go to Applications.scala and method tryAdaptPatternArgs.

2. Modify the method tryAdaptPatternArgs by adding the first line of the body, as follows:

private def tryAdaptPatternArgs(elems: List[untpd.Tree], pt: Type)(using Context): Option[List[untpd.Tree]] =
      if elems.exists(_.@@)
      tryEither[Option[List[untpd.Tree]]]
        (Some(desugar.adaptPatternArgs(elems, pt)))
        ((_, _) => None)

3. Ask for a completion on the position marked by @@

Error stacktrace:

scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
	dotty.tools.dotc.typer.Typer$.assertPositioned(Typer.scala:76)
	dotty.tools.dotc.typer.Typer.typed(Typer.scala:3636)
	dotty.tools.dotc.typer.Applications.extMethodApply(Applications.scala:2630)
	dotty.tools.dotc.typer.Applications.extMethodApply$(Applications.scala:434)
	dotty.tools.dotc.typer.Typer.extMethodApply(Typer.scala:145)
	dotty.tools.dotc.typer.Applications.tryApplyingExtensionMethod(Applications.scala:2675)
	dotty.tools.dotc.typer.Applications.tryApplyingExtensionMethod$(Applications.scala:434)
	dotty.tools.dotc.typer.Typer.tryApplyingExtensionMethod(Typer.scala:145)
	dotty.tools.dotc.interactive.Completion$Completer.tryApplyingReceiverToExtension$1(Completion.scala:561)
	dotty.tools.dotc.interactive.Completion$Completer.$anonfun$23(Completion.scala:604)
	scala.collection.immutable.List.flatMap(List.scala:294)
	scala.collection.immutable.List.flatMap(List.scala:79)
	dotty.tools.dotc.interactive.Completion$Completer.extensionCompletions(Completion.scala:601)
	dotty.tools.dotc.interactive.Completion$Completer.selectionCompletions(Completion.scala:449)
	dotty.tools.dotc.interactive.Completion$.computeCompletions(Completion.scala:221)
	dotty.tools.dotc.interactive.Completion$.rawCompletions(Completion.scala:80)
	dotty.tools.pc.completions.Completions.enrichedCompilerCompletions(Completions.scala:114)
	dotty.tools.pc.completions.Completions.completions(Completions.scala:136)
	dotty.tools.pc.completions.CompletionProvider.completions(CompletionProvider.scala:135)
	dotty.tools.pc.ScalaPresentationCompiler.complete$$anonfun$1(ScalaPresentationCompiler.scala:150)

Short summary:

java.lang.AssertionError: assertion failed: position not set for dotty.tools.dotc.core.Decorators.className(<empty>) # -1 of class dotty.tools.dotc.ast.Trees$Apply in <WORKSPACE>/compiler/src/dotty/tools/dotc/typer/Applications.scala

Expected behaviour:

Should get a non-empty completion from metals.

Operating system:
Linux

Java version:
17.0.13

Editor/extension:
Visual Studio Code v1.95.3

Metals version:
1.4.1

Extra context or search terms:

scala3, completion, dotty

Workspace information:

• Scala versions: 3.6.0; 2.12.20; 2.13.15
• Build tools: 0. sbt
• Build servers:
  0. sbt v1.10.5
• All build tools in workspace: sbt

[tgodzik]

Thanks for reporting! Looks like na issue related to scala/scala3#22217