test6.nim

import macros, strutils

macro `:=`(a, b: expr): stmt {.immediate.} =
  let tempVar = newIdentNode(!"tmp")
  result = newLetStmt(tempVar, b)
  var i = 0
  for child in a.children:
    var arrAccess = newNimNode(nnkBracketExpr)
                    .add(tempVar)
                    .add(newIntLitNode(i))
    if child.kind == nnkExprColonExpr:
      result.add(newVarStmt(child[0], arrAccess))
    elif child.kind == nnkIdent:
      result.add(newVarStmt(child, arrAccess))
    else:
      error("Wrong expr " & treeRepr(child))
    inc i


(var1, var2, var3) := @[1, 2, 3]

dumpTree:
  a[1]