import macros

macro returnsBool(expr: typed): untyped =
  result = newLit(expr.getType.typeKind == ntyBool)
  echo expr.repr, (if result.intVal == 1: " does " else: " doesn't "), "return"

template guard(cond: untyped): untyped =
  when returnsBool(cond):
    if not cond: return
  else:
    try: cond except: return

template guard(cond, body: untyped): untyped =
  when returnsBool(cond):
    if not cond:
      body
      return
  else:
    try: cond except:
      body
      return

import strutils

proc test(x: int, y: string): int =
  guard x > 5
  guard y.len > 0
  result = guard y.strip.parseInt
  echo result
  guard x < 100:
    echo "X is too large!"
  guard result < 255:
    reset result
  block complex:
    echo "Entering complex logic zone"
    result *= 5
    guard x == y.len: break complex
    result = result div 2

echo test(10, "       250")