note, if the value is not 0, 1, 2 then ldc is used instead
5152535455565758596061
if (!returnType.isPrimitive()) { ca.aconstNull(); } else if (returnType == double.class) { ca.dconst(0); } else if (returnType == float.class) { ca.fconst(0); } else if (returnType == long.class) { ca.lconst(0); } else if (returnType == void.class) { // do nothing } else {