Avoid equivalent mutation to unsigned int

[JonathanFoo0523]

Currently, for unsigned integer a, Dredd allow the mutation:

a != 0

to

a > 0

Both expressions are equivalent. Since Dredd has the type information when traversing the AST, it should be possible to disallow such mutation.

[afd]

Do not perform the following mutations:

• a != 0 -> a > 0
• 0 != a -> 0 < a
• a op 0 -> a < 0 (subsumed by false)
• 0 op a -> 0 > a (subsumed by false)
• a op 0 -> a >= 0 (subsumed by true)
• 0 op a -> a <= 0 (subsumed by true)

Am I missing anything else @JonathanFoo0523 @JamesLee-Jones?

[JamesLee-Jones]

Do not perform the following mutations:

• a != 0 -> a > 0
• 0 != a -> 0 < a
• a op 0 -> a < 0 (subsumed by false)
• 0 op a -> 0 > a (subsumed by false)
• a op 0 -> a >= 0 (subsumed by true)
• 0 op a -> a <= 0 (subsumed by true)

Am I missing anything else @JonathanFoo0523 @JamesLee-Jones?

Also:

a == 0 -> a <= 0 (equivalent)
0 == a -> 0 >= a (equivalent)