Presentation Compiler should not fail fast

[rochala]

Compiler version

All

Minimized code

Currently, when crash happens during completions calculation, no results are returned.
In my case, the failure happened in

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)

The crash was encountered during extension member's completion calculation, and all other results were discarded or not computed. This is not ideal, as sometimes crashes are not related strictly to presentation compiler implementation.

The correct output should be a list of completions without extension members (ideally only those that actually crashed)

Reproduction

I tried completing

List(1, 2, 3).map(_.@@) 

in https://github.com/scala/scala3/blob/main/presentation-compiler/src/main/dotty/tools/pc/completions/NamedArgCompletions.scala

With a crash:

java.lang.AssertionError: assertion failed: position not set for dotty.tools.pc.utils.InteractiveEnrichments.companion(<empty>) # -1 of class dotty.tools.dotc.ast.Trees$Apply in <WORKSPACE>/presentation-compiler/src/main/dotty/tools/pc/completions/NamedArgCompletions.scala%

The crash above is not part of this issue, just a fact that presentation compiler should not fail fast.

[Gedochao]

cc @tgodzik @kasiaMarek

[tgodzik]

Would that just be a case of adding a try?

[rochala]

In multiple places, yes. I've discussed this with @kasiaMarek, and it may be good to create a wrapper used for tracking each completion part + we could use this to report timings to find bottlenecks.

But overall it should be a multiple try catch clauses, ideally in every completion step so only one "Contributor" fails a time.