From 09ded3a354c21d4eba9cbc38fdf6327eaa720d24 Mon Sep 17 00:00:00 2001
From: Tyler Yankee <tyler.yankee@kitware.com>
Date: Sun, 23 Aug 2026 13:36:01 -0400
Subject: [PATCH] Help/dev: Note cm::unreachable and CM_UNREACHABLE

Encourage this pattern throughout our sources for optimization and
consistent style.
---
 Help/dev/source.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Help/dev/source.rst b/Help/dev/source.rst
index 1144ee289b..abb26a73c5 100644
--- a/Help/dev/source.rst
+++ b/Help/dev/source.rst
@@ -50,6 +50,9 @@ follow (which are not enforced by other tooling):
 
   * Lambdas: ``auto f = []() {...};``
 
+* Use ``CM_UNREACHABLE`` for logically unreachable code paths instead of
+  ad-hoc ``assert(false ...)`` statements or comment-only placeholders.
+
 C++ Subset Permitted
 ====================
 
@@ -235,6 +238,9 @@ Available features are:
   * ``<cm/type_traits>``:
     ``cm::is_scoped_enum``
 
+  * ``<cm/utility>``:
+    ``cm::unreachable``
+
 Additionally, some useful non-standard extensions to the C++ standard library
 are available in headers under the directory ``cmext/`` in namespace ``cm``.
 These are: