Valid C function pointer declaration is invalid for Swift

C-function-pointer-invalid-in-swift

// I found that when intagrate C API, something strange happending with function declarations

struct testswitf
{
    int (*va_args)(int *I)
};

// end with strange error
// <unknown>:0: error: file.h:100: expected ')'
// <unknown>:0: note: file.h:100: to match this '('

// However after I change it to this, then all is good.

int (*va_args)(int *i);

// the only change I've made is "I" -> "i" in parameters.
// This is strange