gcc/testsuite/g++.dg/modules/cpp-19.C

// { dg-do preprocess }
// { dg-additional-options "-fmodules-ts" }

#define baz(x)
#define qux(x)
export module foo.bar baz(.) . garply qux(:);	// { dg-error "'\\\.' in module name or partition comes from or after macro expansion" }

int i;