gcc/testsuite/g++.dg/modules/block-decl-1_a.C

// { dg-additional-options "-fmodules-ts" }
// { dg-module-cmi bla }

export module bla;

export extern "C++" inline void fun() {
  void oops();  // { dg-bogus "block-scope extern declaration" }
  oops();
}