Guards in `for` loops do not compile

[rfmejia]

for loops in Scala 3 (and 2.x) support guards, however the following does not compile:

def getNums(): UIO[List[Int]] = ZIO.succeed(List(1, 2, 3))
def printNum(n: Int): UIO[Unit] = ZIO.succeed(println(n))
defer {
  for {
    n <- getNums().run
    if n % 2 == 0
  } printNum(n).run // Error: While expanding a macro, a reference to parameter n
}                   // was used outside the scope where it was defined

It seems it has something to do with how guards are desugared, the following also doesn't compile:

defer { 
  getNums().run.withFilter(n => n % 2 == 0).foreach(n => printNum(n).run)
}

whereas replacing withFilter with filter successfully compiles.