3 oneof untainted, tainted
5 tainted reference ==> tainted
6 untainted reference ==> untainted
8 tainted + * ==> tainted
9 * + tainted ==> tainted
11 tainted as untainted ==> error "Possibly tainted storage used as untainted."
12 tainted as tainted ==> tainted
13 untainted as tainted ==> untainted
14 untainted as untainted ==> untainted
16 reference ==> untainted