alternatives error message should not be empty

[scabug]

scala> def getClassSafe(fullName: String): Option[String] = try {
     |                Some(definitions.getClass(newTypeName(fullName)))
     |              } catch {
     |                case _: MissingRequirementError => None
     |              }
<console>:39: error: too many arguments for overloaded method value getClass with alternatives:


                      Some(definitions.getClass(newTypeName(fullName)))
                                               ^

note the cliff hanger, there -- no alternatives are reported

I think the problem is that the getClass symbol is overloaded, but the tree's type is already by the time the error message is synthesized (the error arises from the erroroneous return type Option[String])

Taking the relevant pieces of code:

if (sym.isOverloaded) overloadedMessage

def overloadedMessage = "overloaded method " + sym + " with alternatives:\n" + alternativesString(tree)

def alternativesString(tree: Tree) =
  alternatives(tree) map (x => "  " + methodTypeErrorString(x)) mkString ("", " <and>\n", "\n")

def alternatives(tree: Tree): List[Type] = tree.tpe match {
  case OverloadedType(pre, alternatives)  => alternatives map pre.memberType

this assumes tree.symbol.isOverloaded implies tree.tpe.isInstanceOf[OverloadedType], which this bug illustrates is not necessarily the case

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-6138?orig=1
Reporter: @adriaanm

[scabug]

@hubertp said:
Surprisingly, this is not a regression. I wonder how it survived for so long.

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@JamesIry said:
2.10.2 is about to be cut. Kicking down the road and un-assigning to foster work stealing.

[scabug]

@JamesIry said:
2.10.2 is about to be cut. Kicking down the road and un-assigning to foster work stealing.

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@retronym said:
scala/scala#2578