Documentation only, add 1 example (#18621)

* ReSync with Devel

* ReSync

* Documentation only, add 1 example to For loop macro

* Flip it

* Update doc/manual.rst

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

doc/manual.rst

@@ -5830,6 +5830,27 @@ For loop macro
 A macro that takes as its only input parameter an expression of the special
 type `system.ForLoopStmt` can rewrite the entirety of a `for` loop:
 
+.. code-block:: nim
+    :test: "nim c $1"
+
+  import std/macros
+
+  macro example(loop: ForLoopStmt) =
+    result = newTree(nnkForStmt)    # Create a new For loop.
+    result.add loop[^3]             # This is "item".
+    result.add loop[^2][^1]         # This is "[1, 2, 3]".
+    result.add newCall(bindSym"echo", loop[0])
+
+  for item in example([1, 2, 3]): discard
+
+Expands to:
+
+.. code-block:: nim
+  for item in items([1, 2, 3]):
+    echo item
+
+Another example:
+
 .. code-block:: nim
     :test: "nim c $1"
 
@@ -5866,7 +5887,6 @@ type `system.ForLoopStmt` can rewrite the entirety of a `for` loop:
     echo a, " ", b
 
 
-
 Special Types
 =============