Problem with upgrading to scala 3.4.2 - not sure what to do

[TimPigden]

I formerly had this code:

def ruleGood[T](rule: P[_] => P[T], inString: String, expected: T) = {
    def parseIt[$: P] = rule(P.current) ~ End
    val parsed = parse(inString, parseIt(_))
    assertTrue(parsed.get.value == expected)
  }

invoked by this:

  def testString = test("test string") {
    TestUtils.ruleGood[Expr](Expressions.expr, expr2S, expr2V)
  }

now getting a warning:

Context bounds will map to context parameters.
A `using` clause is needed to pass explicit arguments to them.
This code can be rewritten automatically under -rewrite -source 3.4-migration.
    TestUtils.ruleGood[Statement](Statements.simpleDef, functionDef1, functionDef1V)

I regret to say that the context bound stuff used in fastparse is a total mystery. Any suggestions for fixing my code?