`nkComesFrom` seems deadcode (but used a lot); ok to remove?

[timotheecour]

@Araq
while working on something else I noticed that nkComesFrom is deadcode (never set) even though it's used quite a bit, so removing it would declutter a bit.

• is there any chance nkComesFrom might be revived or is the new code path in wrapInComesFrom strictly better so that nkComesFrom can be removed + its corresponding code cleaned up?
• was the goal of nkComesFrom to produce stacktrace entries for templates/macros as if they were function calls? if so, it would be useful to have it as an option (i had a WIP on that but done differently) but not sure that's what it was about

proc wrapInComesFrom*(info: TLineInfo; sym: PSym; res: PNode): PNode =
  when true:
    result = res
    result.info = info
    if result.kind in {nkStmtList, nkStmtListExpr} and result.len > 0:
      result.lastSon.info = info
    when false:
      # this hack is required to
      var x = result
      while x.kind == nkStmtListExpr: x = x.lastSon
      if x.kind in nkCallKinds:
        for i in 1..<x.len:
          if x[i].kind in nkCallKinds:
            x[i].info = info
  else:
    result = newNodeI(nkStmtListExpr, info)
    var d = newNodeI(nkComesFrom, info)
    d.add newSymNode(sym, info)
    result.add d
    result.add res
    result.typ = res.typ

eg, this code is also dead because of that:

    if it.kind == nkComesFrom:
      if hasNimFrame and frameName == nil:
        inc p.labels
        frameName = "FR" & rope(p.labels) & "_"
        let theMacro = it[0].sym
        add p.s(cpsStmts), initFrameNoDebug(p, frameName,
           makeCString theMacro.name.s,
           quotedFilename(p.config, theMacro.info), it.info.line.int)

as well as initFrameNoDebug + deinitFrameNoDebug + some other code

[Araq]

The idea of ComesFrom is that template expansions do not lose one debug stack frame. As you can see, the implementation was never finished but I think the idea is a good one so I'd rather keep the dead code.

[timotheecour]

just to clarify: so the goal was indeed what i suspected, to treat template/macro calls as if they were function calls, ie:

template bar() = doAssert false
proc fn=bar()
fn()

with nim --stacktracetemplates would produce something like:

stacktrace:
main.nim(1) in bar
main.nim(2) in fn

?

if so, yes, it's a good idea (but i was thinking of a different implementation to achieve that)

if not, please clarify maybe with an example

[Araq]

Yes, exactly.