Example of shutting down ADL.

HappyCerberus · HappyCerberus · commit 0e94f238791b · 2022-09-27T19:26:02.000+02:00
diff --git a/code_examples/theory/CMakeLists.txt b/code_examples/theory/CMakeLists.txt
@@ -21,3 +21,6 @@ add_executable(adl_simple adl_simple.cpp)
 
 add_executable(adl_nonfunc adl_nonfunc.cpp)
 # Compile only
+
+add_executable(adl_shutdown adl_shutdown.cpp)
+# Compile only
diff --git a/code_examples/theory/adl_shutdown.cpp b/code_examples/theory/adl_shutdown.cpp
@@ -0,0 +1,4 @@
+#include "adl_shutdown_code.h"
+int main() {
+    calling_site();
+}
diff --git a/code_examples/theory/adl_shutdown_code.h b/code_examples/theory/adl_shutdown_code.h
@@ -0,0 +1,13 @@
+namespace Custom {
+    struct X {
+        friend void some_func(const X&) {}
+    };
+}
+
+constexpr inline auto some_func = [](const auto&) {};
+
+void calling_site() {
+    Custom::X x;
+    some_func(x); // calls ::some_func
+    // Because ::some_func prevents ADL, Custom::some_func cannot be called.
+}
