Support for .?[] operator on openArrays

questionable/indexing.nim

@@ -1,16 +1,23 @@
 import std/macros
 
-macro `.?`*(expression: seq | string, brackets: untyped{nkBracket}): untyped =
+macro `.?`*(expression: seq | string | openArray, brackets: untyped{nkBracket}): untyped =
   # chain is of shape: (seq or string).?[index]
   let index = brackets[0]
   quote do:
     block:
       type T = typeof(`expression`[`index`])
-      let evaluated = `expression`
-      if `index` < evaluated.len:
-        evaluated[`index`].some
+
+      when typeof(`expression`) is openArray:
+        if `index` >= `expression`.low and `index` <= `expression`.high:
+          `expression`[`index`].some
+        else:
+          T.none
       else:
-        T.none
+        let evaluated = `expression`
+        if `index` >= evaluated.low and `index` <= evaluated.high:
+          evaluated[`index`].some
+        else:
+          T.none
 
 macro `.?`*(expression: typed, brackets: untyped{nkBracket}): untyped =
   # chain is of shape: expression.?[index]

testmodules/options/test.nim

@@ -337,13 +337,23 @@ suite "optionals":
 
   test ".?[] can be used for indexing strings without raising IndexDefect":
     let str = "a"
-    check str.?[0] == 'a'.some 
+    check str.?[0] == 'a'.some
     check str.?[1] == char.none
+    check str.?[-1] == char.none
 
   test ".?[] can be used for indexing sequences without raising IndexDefect":
     let sequence = @[1]
     check sequence.?[0] == 1.some
     check sequence.?[1] == int.none
+    check sequence.?[-1] == int.none
+
+  test ".?[] can be used for indexing openArrays without raising IndexDefect":
+    proc checkOpenArray(oa: openArray[int]): void =
+      check oa.?[0] == 1.some
+      check oa.?[1] == int.none
+      check oa.?[-1] == int.none
+
+    checkOpenArray(@[1])
 
   test ".?[] can be followed by calls, operators and indexing":
     let table = @{"a": @[41, 42]}.toTable