Hotfix 3.3.3

[Kordyjan]

Fixes #19815

contents:

• [c5169f0] - fix by @smarter
• [1f5a667] - forward and backward compatibility tests (by @bishabosha). Probably, it's overkill, but it's better to be paranoid than sorry. They only take a few seconds.
• [df10488] - a copy of the 3.3.2 changelog with annotation about the hotfix.
• [e497a42] - version bump. I decided to stay on 3.3.1 as a reference version and version that we check the compatibility against.

[ritschwumm]

typo: "treverser" should probably be "traverser"

[bishabosha]

@Kordyjan just a note on this fix, I think we should still do something about the unique name counters for 3.4, it seems ultimately it works due to shadowing rules, but you do get some weird code gen:

class Test {
  def foo[T: Numeric]: String ?=> T = summon[Numeric[T]].fromInt(summon[String].length)
}

by typer we have

package <empty> {
  class Test() extends Object() {
    def foo[T >: Nothing <: Any](implicit evidence$1: Numeric[T]):
      (String) ?=> T =
      {
        def $anonfun(using evidence$1: String): T =
          evidence$1.fromInt(evidence$1.length())
        closure($anonfun)
      }
  }
}

i.e. evidence$1.fromInt(evidence$1.length()) looks very strange, however this seems to be safe because its encoded with direct symbol references when you reach TASTy

    86:         BLOCK(57)
    88:           LAMBDA(2)
    90:             TERMREFdirect 92
    92:           DEFDEF(51) 23 [$anonfun]
    95:             PARAM(4) 17 [[Unique evidence$ 1]]
    98:               SHAREDtype 76
   100:               GIVEN
   101:             SHAREDtype 65
   103:             APPLY(38)
   105:               SELECTin(17) 27 [fromInt[Signed Signature(List(scala.Int),java.lang.Object) @fromInt]]
   108:                 INLINED(10)
   110:                   INLINED(2)
   112:                     TERMREFdirect 50  // ref to the parameter evidence$1
   114:                   IDENTtpt 28 [Predef[ModuleClass]]
   116:                     TYPEREF 28 [Predef[ModuleClass]]
   118:                       SHAREDtype 30
   120:                 TYPEREF 18 [Numeric]
   122:                   TERMREFpkg 30 [scala[Qualified . math]]
   124:               APPLY(17)
   126:                 SELECTin(15) 32 [length[Signed Signature(List(),scala.Int) @length]]
   129:                   INLINED(8)
   131:                     INLINED(2)
   133:                       TERMREFdirect 95 // ref to the parameter evidence$1
   135:                     IDENTtpt 28 [Predef[ModuleClass]]
   137:                       SHAREDtype 116
   139:                   TYPEREF 21 [String]
   141:                     SHAREDtype 20

then by genBCode we have flattened the parameter lists

package <empty> {
  @SourceFile("Test.scala") class Test extends Object {
    def <init>(): Unit =
      {
        super()
        ()
      }
    @ContextResultCount(1) def foo(implicit evidence$1: scala.math.Numeric,
      evidence$1: String): Object = evidence$1.fromInt(evidence$1.length())
  }
}