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

=> moved to https://github.com/nim-lang/Nim/issues/8649 (caseStmtMacros and ifStmtMacros to support C#8-like Recursive Patterns matching (Deconstruction Pattern))

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