Const asserts

[ds84182]

Today I encountered an issue where I needed to ensure that some constants are edited correctly to prevent a runtime error. While it's possible to write a StaticAssert class like this:

class StaticAssert {
  const StaticAssert(bool value, [String message = 'Assertion failed']) : assert(value, message);
}

Using it is somewhat difficult, since the analyzer complains about unused variables:

const _asserts = [
  _StaticAssert(a <= b),
  _StaticAssert(c <= b),
];

It would be a bit better if you could write a top level assert:

const assert(a <= b);
const assert(c <= b);

Which is sorta like static_assert in C++11.

[munificent]

Your StaticAssert class is a really clever trick to approximate static_assert. :)

What kind of real code are you using this for? Since the expression itself must be constant, I'm having a hard time imagining practical uses for it.

[ds84182]

We have a couple of animation durations in milliseconds. We want to ensure that our max duration constant is >= all of the durations. Since there's no good way to do a compile time 'max' other than nested ternaries, we use static assert to make sure none of the constants were changed to be larger than the max duration, which would cause a runtime error.