Manually check struct invariants

[Ali Çehreli]

On 3/23/21 4:14 PM, Imperatorn wrote:> On Tuesday, 23 March 2021 at 
22:22:12 UTC, Q. Schroll wrote:
 >> For a class object obj, one can use assert(obj) to get its invariants
 >> checked. How to do this for structs?
 >
 > It's called after the constructor has run and before the destructor is
 > called.
 >
 > It's called before entering a member function and after exiting a member
 > function.
 >
 > So technically you could just do like obj.writeln or whatever u have 😁

Just to make sure everyone knows "it" is the invariant block:

struct S {
   int i;
   int j;

   this(int i, int j) {
     this.i = i;
     this.j = j;
   }

   invariant() {
     assert(i == 2 * j);
   }
}

void main() {
   auto s = S(1, 10);    // Won't pass the invariant check
}

Ali