Add proc `[]`(n: NimNode, s: HSlice[T, U]): seq[NimNode] to macros (#7735)

fixes #7670.

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/core/macros.nim b/lib/core/macros.nim
index 3011eaa67..2508a889e 100644
--- a/lib/core/macros.nim
+++ b/lib/core/macros.nim
@@ -168,6 +168,18 @@ proc `[]`*(n: NimNode, i: int): NimNode {.magic: "NChild", noSideEffect.}
 proc `[]`*(n: NimNode, i: BackwardsIndex): NimNode = n[n.len - i.int]
   ## get `n`'s `i`'th child.
 
+template `^^`(n: NimNode, i: untyped): untyped =
+  (when i is BackwardsIndex: n.len - int(i) else: int(i))
+
+proc `[]`*[T, U](n: NimNode, x: HSlice[T, U]): seq[NimNode] =
+  ## slice operation for NimNode.
+  ## returns a seq of child of `n` who inclusive range [n[x.a], n[x.b]].
+  let xa = n ^^ x.a
+  let L = (n ^^ x.b) - xa + 1
+  result = newSeq[NimNode](L)
+  for i in 0..<L:
+    result[i] = n[i + xa]
+
 proc `[]=`*(n: NimNode, i: int, child: NimNode) {.magic: "NSetChild",
   noSideEffect.}
   ## set `n`'s `i`'th child to `child`.