Missing dot-completion on higher-order function

[harpocrates]

Describe the bug

Given this self-contained code snippet:

class Foo {
  def Bar: Double = 2.0
  def Baz: Double = 1.0
}

object Bar {
  
  def higherOrder1(f: Foo => Double): Nothing = ???
  def higherOrder2(f: Foo => Double, s: String): Nothing = ???
}

Then, if I try to call higherOrder2 the suggested completions for an anonymous function are missing:

  higherOrder1(_. )
  //             ^ cursor is here   
  // I correctly see `Bar: Double` and `Baz: Double` being suggested

  higherOrder2(_. )
  //             ^ cursor is here   
  // I don't see either `Bar: Double` or `Bar: Double` being suggested
}

Note that if I fill in the second argument of higherOrder2, completions do start showing up when I go back to the first parameter (but that's inconvenient - I usually expect to just type from left to write - not filling in a parameter then hopping back to the first parameter after).

Expected behavior

I would like to see all of the same completions for higherOrder1 as higherOrder2.

Operating system

macOS

Editor/Extension

VS Code

Version of Metals

1.1.0

Extra context or search terms

No response

[tgodzik]

Thanks for reporting! It seems that the presentation compiler for Scala 2 is at fault here, but I made a workaround in Metals.

[tgodzik]

After double checking the PR it seems we need to fix it in the compiler itself.

I suspect migrating https://github.com/lampepfl/dotty/pull/14695/files to Scala 2 would be needed. I don't think I will be able to work on that any time soon.

[tgodzik]

Reported it upstream in scala/bug#12909