[Completions] Fix duplicated methods from implicit conversions

[dos65]

Fixes the following case:

Array(1,2,3).fil@@

Before this fix there were several filter and filterNot methods in
completions they were taken from all eligible implicit candidates.

Now there is a kind of ranking per denotation.

[prolativ]

In general this looks like going in the right direction but the solution seems quite incomplete by handling only methods from implicit conversions but not new style extension methods. To verify the results I would recommend adding the tests cases like this

  @Test def methodFromImplicitConversionWithBestResultType : Unit =
    code"""|implicit class OptionWrap(i: Int):
           |  def wrap: Option[Int] = Some(i)
           |
           |implicit class SeqWrap(i: Int):
           |  def wrap: Seq[Int] = Seq(i)
           |
           |val w: Option[Int] = 1.wr${m1}
           |""".withSource
      .completion(m1, Set(("wrap", Method, "=> Option[Int]")))
      
  @Test def extensionMethodWithBestResultType : Unit =
    code"""|given optionWrap: {} with
           |  extension (i: Int) def wrap: Option[Int] = Some(i)
           |
           |given seqWrap: {} with
           |  extension (i: Int) def wrap: Seq[Int] = Seq(i)
           |
           |val w: Option[Int] = 1.wr${m1}
           |""".withSource
      .completion(m1, Set(("wrap", Method, "=> Option[Int]")))

[dos65]

@prolativ Thx! I thought to check other cases too but wasn't sure if solution is valid. Will cover the suggested samples.

[prolativ]

Other cases that we should consider and test:

• One method coming from an extension and one from an implicit conversion
• If there is an ambiguity in implicits (e.g. when you remove the explicit type annotation from val w in my examples) - we should probably include both alternatives in the completions - here also one method might come from an extension and the other from an implicit conversion.
  In case of any doubts how some corner cases should be handled just try to compile some code and check which signatures are chosen by the compiler

[tgodzik]

Closing and leaving and open issue