Is it time for D 3.0?

[Steven Schveighoffer]

There have been a lot of this pattern happening:

1. We need to add feature X, to fix problem Y.
2. This will break ALL CODE IN EXISTENCE
3. OK, cancel the fix, we'll just live with it.

Having a new branch of the compiler will provide a way to keep D2 
development alive while giving a playground to add new mechanisms, fix 
long-existing design issues, and provide an opt-in for code breakage.

Some issues I can think of:

1. The safe by default debate
2. pure by default
3. nothrow by default
4. String interpolation DIP
5. auto-decoding
6. range.save
7. virtual by default
8. ProtoObject

Other languages evolve much quicker than D, but break things only in 
major updates. D seems to "sort of" break things, there's always a risk 
in every release. We try to be conservative, but we have this horrible 
mix of deciding some features can break things, while others are not 
allowed to, and there's no clear guide as to which breakage fits in 
which category.

If we went to a more regular major release schedule, and decided for a 
roadmap for each major release what features would be included, it would 
allow much better planning, and much more defensible breakage of code. 
If you know that your code will only compile with D2.x, and you're fine 
with that, then great, don't upgrade to D3.x. If you desperately want a 
feature, you may have to upgrade to D3.x, but once you get there, you 
know your code is going to build for a while.

We could also not plan for many major releases, but at least move to D3 
for some major TLC to the language that is held back to prevent breakage.

I work occasionally with Swift, and they move very fast, and break a lot 
of stuff, but only in major versions. It's a bit fast for my taste, but 
it seems to work for them. And they get to fix issues that languages 
like C++ might have been stuck with forever.

The biggest drawback is that we aren't a huge language, with lots of 
manpower to keep x branches going at once.

I just wanted to throw it out as a discussion point. We spend an awful 
lot of newsgroup server bytes debating things that to me seem obvious, 
but have legitimate downsides for not breaking them in a "stable" language.

-Steve