llvm-project/clang/test/PCH/replaced-decl.m

// Without PCH
// RUN: %clang_cc1 -fsyntax-only -verify %s -include %s -include %s

// With PCH
// RUN: %clang_cc1 -fsyntax-only -verify %s -chain-include %s -chain-include %s

#ifndef HEADER1
#define HEADER1

@class I;

#elif !defined(HEADER2)
#define HEADER2

@interface I
@end

#else

typedef int I; // expected-error {{redefinition}}
               // expected-note@15 {{previous}}

#endif