hanchenye-llvm-project/clang/test/Sema/exprs.c

// RUN: clang %s -verify -pedantic -fsyntax-only

// PR1966
_Complex double test1() {
  return __extension__ 1.0if;
}

_Complex double test2() {
  return 1.0if;    // expected-warning {{imaginary constants are an extension}}
}