Fix -Wunused:import registering constructor ("<init>") instead of its owner (also fix false positive for enum)

[PaulCoral]

This solves the issue #16650.

The issue is that member(sym.name) failed to resolve when a type contains multiple identical name. Here the dotty.tools.dotc.util package contains multiple "" (constructor), so member fail to resolve the name

The solution is to register the owner of the contructor instead of the constructor itself.

⚠️ I couldn't create a test where this appends, I tested it by publishLocal and testing the code in a different project with this code from #16650 (also didn't check on the metals build):

//> using lib "org.scala-lang::scala3-compiler:3.3.0-RC1-bin-20230109-f56089b-NIGHTLY"
//> using scala "3.3.0-RC1-bin-20230109-f56089b-NIGHTLY"
//> using option "-Wunused:all"

import dotty.tools.dotc.util.LinearSet

@main
def run = 
  val a = 123
  println("Hello!")

sbt> run
[info] compiling 1 Scala source to .../target/scala-3.3.0-RC1-bin-SNAPSHOT/classes ...
[warn] -- Warning: ..../src/main/scala/Main.scala:5:29 
[warn] 5 |import dotty.tools.dotc.util.LinearSet
[warn]   |                             ^^^^^^^^^
[warn]   |                             unused import
[warn] -- Warning:.../src/main/scala/Main.scala:10:6 
[warn] 10 |  val a = 123
[warn]    |      ^
[warn]    |      unused local definition
[warn] two warnings found
[info] running run 
Hello!

EDIT

Also add a related fix for import generated by enum (false positive)

[PaulCoral]

Added a small fix also related to -Wunused:import issue (false positive enum). fa1d2bb

[szymon-rd]

I wasn't able to come up with a reproduction that we could run with vulpix. I managed to get rid of the compiler dependency but there still has to be a jar file for this to crash: #16666. Let's wait another day and see if somebody has something to say there, if there is no development I think we will have to merge it without a regression test. Otherwise, all looks good to me!

[szymon-rd]

It's ok to merge IMO given that we found the core problem and have a way to address it.

[PaulCoral]

It's ok to merge IMO given that we found the core problem and have a way to address it.

Also the additional fix for enums is important at it fixes a common cause of false positive.