🧑‍💻 "static_warning"

Marlin/src/inc/Warnings.cpp

@@ -31,6 +31,24 @@
 // Warnings! Located here so they will appear just once in the build output.
 //
 
+// static_warning works like a static_assert but only emits a (messy) warning.
+#ifdef __GNUC__
+  namespace mfwarn {
+    struct true_type {};
+    struct false_type {};
+    template <int test> struct converter : public true_type {};
+    template <> struct converter<0> : public false_type {};
+  }
+  #define static_warning(cond, msg) \
+    struct CAT(static_warning, __LINE__) { \
+      void _(::mfwarn::false_type const&) __attribute__((deprecated(msg))) {}; \
+      void _(::mfwarn::true_type const&) {}; \
+      CAT(static_warning, __LINE__)() {_(::mfwarn::converter<(cond)>());} \
+    }
+#else
+  #define static_warning(...)
+#endif
+
 #if ENABLED(MARLIN_DEV_MODE)
   #warning "WARNING! Disable MARLIN_DEV_MODE for the final build!"
   #ifdef __LONG_MAX__