[Someone]

So Dart is moving in the Swift direction, which has

    if let value = value {
      // a new binding named ‘value’ refers to value, unwrapped 
    }

or (newer syntax that I initially found even weirder than the older one, but both grew on me)

    if let value {
      // a new binding named ‘value’ refers to value, unwrapped 
    }

(The old version will remain, as it is more flexible, allowing such things as

    if let baz = foo.bar(42) {
      // a new binding named ‘baz’ refers to foo.bar(42), unwrapped 
    }
)