caseStmtMacros.nim

{.experimental: "caseStmtMacros".}

import macros

macro match(n: tuple): untyped =
  result = newTree(nnkIfStmt)
  let selector = n[0]
  for i in 1 ..< n.len:
    let it = n[i]
    case it.kind
    of nnkElse, nnkElifBranch, nnkElifExpr, nnkElseExpr:
      result.add it
    of nnkOfBranch:
      for j in 0..it.len-2:
        let cond = newCall("==", selector, it[j])
        result.add newTree(nnkElifBranch, cond, it[^1])
    else:
      error "'match' cannot handle this node", it
  echo repr result

case ("foo", 78)
of ("foo", 78): echo "yes"
of ("bar", 88): echo "no"
else: discard

Well match can rewrite the case statement in any way you see fit, it can introduce binding to locals or "don't care" symbols.

But supporting _ placeholder is very useful, would be nice to support it

++++1

=> moving discussion to somwhere more visible in https://github.com/nim-lang/Nim/issues/8649