The first stage of the formal review for DIP 1006 [1], "Providing more selective control over contracts", is now underway. From now until 11:59 PM ET on September 29(3:59 AM GMT on September 30), the community has the opportunity to provide last-minute feedback. If you missed the preliminary review round [2], this is your chance to provide input.

At the end of the feedback period, I will submit the DIP to Walter and Andrei for their final decision. Thanks in advance to those of you who participate.

[1] https://github.com/dlang/DIPs/blob/master/DIPs/DIP1006.md

[2] http://forum.dlang.org/post/rsafosvkhxddkxptaziy@forum.dlang.org

On Friday, 15 September 2017 at 14:25:56 UTC, Mike Parker wrote:
> The first stage of the formal review for DIP 1006 [1], "Providing more selective control over contracts", is now underway. From now until 11:59 PM ET on September 29(3:59 AM GMT on September 30), the community has the opportunity to provide last-minute feedback. If you missed the preliminary review round [2], this is your chance to provide input.
>
> At the end of the feedback period, I will submit the DIP to Walter and Andrei for their final decision. Thanks in advance to those of you who participate.
>
> [1] https://github.com/dlang/DIPs/blob/master/DIPs/DIP1006.md
>
> [2] http://forum.dlang.org/post/rsafosvkhxddkxptaziy@forum.dlang.org

"invariants stand out in that regard: they can be used on a pay-for-what-you-use basis, by using assert(object) (or assert(this)), but they are also implicitly called twice on every public and protected class method call. The call itself is not direct: the compiler inserts a call to _d_invariant, which can be found in druntime."

On DMD 2.076.0, it's once per public method (inserted into the method body just before returning). Awkwardly, this is still done for final classes with no invariants defined locally or in base classes...

Changing it to a virtual function call, eliminating it for final classes when possible, etc would greatly reduce the cost. But may as well go whole hog.