1 files changed, 28 insertions, 1 deletions
diff --git a/lib/system.nim b/lib/system.nim
index 5a84f4a52..00eae7337 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -669,6 +669,12 @@ proc newSeq*[T](len = 0.Natural): seq[T] =
   ##   #inputStrings[3] = "out of bounds"
   newSeq(result, len)
 
+proc newSeqOfCap*[T](cap: Natural): seq[T] {.
+  magic: "NewSeqOfCap", noSideEffect.} =
+  ## creates a new sequence of type ``seq[T]`` with length 0 and capacity
+  ## ``cap``.
+  discard
+
 proc len*[TOpenArray: openArray|varargs](x: TOpenArray): int {.
   magic: "LengthOpenArray", noSideEffect.}
 proc len*(x: string): int {.magic: "LengthStr", noSideEffect.}
@@ -1523,7 +1529,7 @@ type # these work for most platforms:
     ## This is the same as the type ``unsigned long long`` in *C*.
 
   cstringArray* {.importc: "char**", nodecl.} = ptr
-    array [0..ArrayDummySize, cstring]
+    array[0..ArrayDummySize, cstring]
     ## This is binary compatible to the type ``char**`` in *C*. The array's
     ## high value is large enough to disable bounds checking in practice.
     ## Use `cstringArrayToSeq` to convert it into a ``seq[string]``.
@@ -3633,6 +3639,27 @@ proc `==` *(x, y: cstring): bool {.magic: "EqCString", noSideEffect,
   elif x.isNil or y.isNil: result = false
   else: result = strcmp(x, y) == 0
 
+template closureScope*(body: untyped): stmt =
+  ## Useful when creating a closure in a loop to capture local loop variables by
+  ## their current iteration values. Example:
+  ##
+  ## .. code-block:: nim
+  ##   var myClosure : proc()
+  ##   # without closureScope:
+  ##   for i in 0 .. 5:
+  ##     let j = i
+  ##     if j == 3:
+  ##       myClosure = proc() = echo j
+  ##   myClosure() # outputs 5. `j` is changed after closure creation
+  ##   # with closureScope:
+  ##   for i in 0 .. 5:
+  ##     closureScope: # Everything in this scope is locked after closure creation
+  ##       let j = i
+  ##       if j == 3:
+  ##         myClosure = proc() = echo j
+  ##   myClosure() # outputs 3
+  (proc() = body)()
+
 {.pop.} #{.push warning[GcMem]: off, warning[Uninit]: off.}
 
 when defined(nimconfig):