grep: Unmatched ) or \)

but your main point might be right; the few non-method matches to (pcre) '\)\s*\w+\s*\(' in /usr/share/go-1.19 seem to be uncommon things like this:

    static void __attribute__ ((constructor)) sigsetup(void) {
    void poison() __attribute__ ((weak));
    C3 = -(R + I) // ADD(5,6) NEG(-5,-6)