wrong error: `is of type 'NimNode' and has to be used (or discarded)` in else branch

This code is mostly self-explanatory, I really don't understand why that error happens :)

Example

import macros

macro test*(): untyped =   
  let b = @[1, 2, 3, 4]

  result = nnkStmtList.newTree()
  var i = 0
  while i < b.len:
    if false:
      # this quote do is mandatory, removing it fixes the problem
      result.add quote do:
        let testtest = 5
    else:
      result.add quote do:
        let test = 6
      inc i
      # removing this continue fixes the problem too
      continue
    inc i

test()

Current Output

/home/dian/Projects/nim-snippets/tt.nim(14, 7) Error: expression '
add(result, getAst(`:anonymous`(newIdentNode("result"))))
inc i, 1
continue' is of type 'NimNode' and has to be used (or discarded); start of expression here: /home/dian/Projects/nim-snippets/tt.nim(9, 5)

Expected Output

No error

Additional information

Confirmed that it worked in 1.0.6 via the playground.

$ nim -v
Nim Compiler Version 1.3.5 [Linux: amd64]
Compiled at 2020-06-14
Copyright (c) 2006-2020 by Andreas Rumpf

git hash: d749c8cd87508871dc28b528f57d26b1004007b3
active boot switches: -d:release -d:danger

import macros

macro test*(): untyped =   
  for i, x in @[1, 2, 3]:
    if false:
      # this quote do is mandatory, removing it fixes the problem
      result.add quote do:
        discard
    else:
      echo "hi"
      # removing this continue fixes the problem too
      continue

test()

A bit shorter example

git bisect showed c79df2f as the first bad commit, and by the looks of it that commit might be related to the issue.

[timotheecour]

• this is unrelated to quote do

when defined case2c:
  import macros
  proc fn(): NimNode =
    var z: NimNode
    for i in 0..2:
      if false:
        add(result, z)
      else:
        discard
        # either break, return, continue would give error
        break

Error: expression '
discard
break' is of type 'NimNode' and has to be used (or discarded); start of expression here:

note: seems specific to NimNode

no error here; this is strage.

when defined case3:
  import macros
  type Foo = object
  proc fn(): seq[Foo] {.compileTime.} =
    for i in 0..2:
      if false:
        add(result, Foo())
      else:
        discard
        break

[shirleyquirk]

indeed i think this is the same issue as #19150.
if you discard result.add z the error disappears:

import macros
proc fn(): NimNode =
  var z: NimNode
  for i in 0..2:
    if false:
      discard add(result, z)
    else:
      discard
        # either break, return, continue would give error
      break

[metagn]

This is not specific to NimNode.

proc add2(a: var seq[int], b: int): int =
  a.add(b)
  b

proc fn(): seq[int] =
  for i in 0..2:
    if false:
      add2(result, i)
    else:
      discard
      break

Same error with or without discardable, saying expression ' discard break' is of type 'int' and has to be used (or discarded); , which is the wrong error. There might be another open issue for this (I know there is one for try/finally).