test1.nim

import macros

macro optRepeat{repeat(value, num)}(value: untyped, num: static[int]): untyped =
  echo "static repeat called"
  result = newNimNode(nnkBracket)
  for i in 1..num:
    result.add(value)

proc repeat[T](value: T, num: int): seq[T] =
  echo "dynamic repeat called"
  result = newSeqOfCap[T](num)
  for i in 0..<num:
    result.add(value)

var myArr = [1, 2, 3, 4, 5, 6]
var a = 3

myArr[0..1] = repeat(42, 2)
myArr[3..5] = repeat(42, a)

echo @myArr

import macros

macro optRepeat{repeat(value, num)}(value: untyped, num: int{lit}): untyped =
  echo "static repeat called"
  result = newNimNode(nnkBracket)
  for i in 1..num.intVal:
    result.add(value)

proc repeat[T](value: T, num: int): seq[T] =
  echo "dynamic repeat called"
  result = newSeqOfCap[T](num)
  for i in 0..<num:
    result.add(value)

var myArr = [1, 2, 3, 4, 5, 6]
var a = 3

myArr[0..1] = repeat(42, 2)
myArr[3..5] = repeat(42, a)

echo @myArr

macro optRepeat{`[]=`(x, `..`(a, b)) = repeat(value, num)}(x, a, b, value: untyped, num: int{lit}): untyped =
  echo "static repeat called"
  result = newNimNode(nnkStmtList)
  template singleAsgn(x, a, i, val) =
    x[a+i] = val
  for i in 1..num.intVal:
    result.add(getAst singleAsgn(x, a, newLit i, value))