Mutability of functions

[Jomy10]

Just a thought here:

Just like making a function static by capitalising it, instead of writing mut func, a mutable function will be indicated by a !, like in Ruby, with the difference here that it will be obligatory. So declaring a function that mutates the struct it is called on:

func mutatingFunc!() {}

myStruct.mutatingFunc!{}

The compiler should give warnings when the function doesn't mutate the underlying struct