how to get pragma of the field in macro?

[aiac]

i try to use `fieldPairs()`, but unfortunately
    
    
    macro parse(a: typed; k: untyped): untyped =
      result = nnkCaseStmt.newTree(k)
      for fk, fv in a.fieldPairs():
        when fv.hasCustomPragma(opt):
          result.add nnkOfBranch.newTree(
              newLit(fk), nnkStmtList.newTree(nnkAsgn.newTree(fv, newLit("🤔")))
            )
      result.add nnkElse.newTree(
          nnkStmtList.newTree(nnkDiscardStmt.newTree(newEmptyNode()))
        )
     
    
    Run

> 
>     Expression: fieldPairs(a)
>       [1] a: NimNode
>     
>     Expected one of (first mismatch at [position]):
>     [1] iterator fieldPairs[S: tuple | object; T: tuple | object](x: S; y: 
> T): tuple[
>         key: string, a, b: RootObj]
>     [1] iterator fieldPairs[T: tuple | object](x: T): tuple[key: string, val: 
> RootObj]
>      
>      
>     
>     Run