stringLiteralBit.nim

type
  SeqHeader = object
    len, reserved: int

proc isLiteral(s: string): bool {.inline.} = (cast[ptr SeqHeader](s).reserved and (1 shl (sizeof(int)*8 - 2))) != 0


proc main(param: string) =
  echo "param ", isLiteral(param)

echo "const ", isLiteral("foobar")
main("const here")

var x: string = "foo bar"
main(x)