Re: DIP 1018--The Copy Constructor--Formal Review
On Monday, 25 February 2019 at 02:56:13 UTC, Walter Bright wrote: Your DIP, and nobody else is going to do it, so it falls to me. It will be reviewed at Dconf, please make sure you have an _accurate_ summary of your criticisms of the DIP ready for then. BTW, everyone should expect the DIP process to be brutal. No! It should be thorough, that is a critical distinction. It has to be, we're long past the stage where we can allow misshapen stuff to get into the language. Nobody was very kind with my bottom type DIP :-) Perhaps because you responded to _precisely none_ of the feedback and wasted everybody's time? You should read the dismissal of mine and Andrei's "static if" proposal for C++! (Ironically, it was later adopted after someone else redid it, after removing one of its keystone features.) I have, it is hysterical in all senses to the word. I don't see how that relates to any of this.
mysql-native v2.3.0 - With a request for assistance
Small update to mysql-native (A fully-D client library for MySQL/MariaDB that doesn't depend on any external MySQL/MariaDB libs). The most interesting thing in v2.3.0 is that, thanks to @jpf91, the column names for a result set can now be obtained directly from the Row (via `Row.getName(columnIndex)`). Aside from that, this release just involves some internal cleanups (with much more still to come) and a rather major reworking of the test runner script. -- One important note for mysql-native users to be aware of (And this goes for all of mysql-native, not just this particular version): Starting with MySQL Server v8.0.4, the server's default authentication mechanism was changed. Unfortunately, mysql-native does not yet support this new authentication style. For now, if you have sufficient admin privileges for your DB server, you can temporarily work around the issue like this: https://dev.mysql.com/doc/refman/8.0/en/upgrading-from-previous-series.html#upgrade-caching-sha2-password-compatibility-issues Naturally, I consider fixing this the current top priority for mysql-native. But as I've been rather busy lately I haven't had as much time for this as I would like, so I would encourage any able-bodied coders to please beat me to it! Other mysql-native users will be appreciative. More details on the issue here: https://github.com/mysql-d/mysql-native/issues/189 -- mysql-native Home on GitHub: https://github.com/mysql-d/mysql-native mysql-native on Dub: http://code.dlang.org/packages/mysql-native mysql-native API reference: http://semitwist.com/mysql-native
Re: DIP 1018--The Copy Constructor--Formal Review
On 2/24/2019 8:04 PM, Manu wrote:
1. make code easier to understand?
const code is self documenting and protective against modification by
issuing the user helpful error messages.
I've had many people tell me they mean transitive const when they use const in
C++. That is not self documentation. Nor is it very helpful. The very fact that
const code compiles in C++ and surprises people when it doesn't compile in D
shows the misunderstanding it engenders in C++ code. People infer that it is
transitive when it is not.
Really, of what value is it to know that only the head can't be changed, with no
information about the rest?
An interesting manifestation of this uselessness in C++ is the notion of
"logical const", where a supposedly "const" value is lazily set to a value upon
first use. I.e. it isn't const, it's just pretend const.
2. prevent common programming bugs?
You can't modify const data, for instance,
I know technically what it does. But that wasn't my question.
a copy constructor can't freely modify the source value...
C++ copy constructors are not required to declare the source as const:
"A non-template constructor for class X is a copy constructor if its first
parameter is of type X&, const X&, volatile X& or const volatile X&, and either
there are no other parameters or else all other parameters have default arguments"
-- CPP98.12.8
Again, I know technically what it does. Not the value of it. I used C for a
decade before const was introduced. I tried using it, and discovered that head
const added nothing much of any value and I stopped bothering with it.
3. help with multithreaded coding problems?
This is a different conversation about `immutable` and `shared`.
`const` doesn't say anything about D's decisions relating to
thread-locality by default, which obviously still applies.
'immutable' data is implicitly shareable. Const allows the same functions to
work on both shared immutable and non-shared mutable data. C++ has no way to say
a function can work on both kinds of data, or even how to describe such data.
4. improve code generation?
Not a lot.
Actually, not at all. C++ const is useless for code generation because:
1. people cast away const (yes, they do!). I learned this the hard way and had
to back out those optimizations.
2. other references may mutate it.
Because of (2) it is similarly useless in D, however, it allows the same
functions to work on immutable and mutable data, and that does have value. (The
optimizer can make use of immutable.)
I mean, you speak as if `const` is a synonym for `mutable` in C++...
const things are const.
Not only are they not (legal to cast it away!), they can be mutated by other,
non-const pointers. (There's no way to specify "pointer to immutable" in C++.)
Furthermore, const tells you nothing about the rest of the data structure. C++
const is all fine if your data structure fits entirely in one struct. It's
rather meaningless for more complex objects. You cannot write generic code:
void doSomething(T)(const T x) {...}
and rely on it to not modify T if T is a non-trivial object.
Alternatively, if const were spec-ed similar to C++ const, it would be
very easy to implement TransitiveConst!T as a tool.
You could specify it, but you couldn't use it. (There'd be all kinds of implicit
conversion problems.) There's good reason why const is treated specially for
overload resolution and implicit conversion. I.e.:
void foo(const T const * const * const * p);
const T * const * const * q;
foo(q); // oops!
One thing I quite agree with you on, though, if you really want to modify
non-trivial const objects, then D's const isn't for you :-) If you don't believe
the rewards of carefully designing the data structures and functions that
operate on them so they can be const is worth it, then D's const isn't for you.
For me, I think it is worth it. And yes, it ain't easy, as old habits die hard.
Re: DIP 1018--The Copy Constructor--Formal Review
On Sun, Feb 24, 2019 at 6:35 PM Walter Bright via
Digitalmars-d-announce wrote:
>
> I agree with your point that C++ const can be used in a lot more places than D
> const. Absolutely true.
>
> Missing from the post, however, is an explanation of what value C++ const
> semantics have. How does it:
>
> 1. make code easier to understand?
const code is self documenting and protective against modification by
issuing the user helpful error messages.
> 2. prevent common programming bugs?
You can't modify const data, for instance, a copy constructor can't
freely modify the source value...
> 3. help with multithreaded coding problems?
This is a different conversation about `immutable` and `shared`.
`const` doesn't say anything about D's decisions relating to
thread-locality by default, which obviously still applies.
Maybe you're trying to argue that a const object which contains an
escape-pointer to mutable data may lead to races? But that's not the
case, because all data is thread-local in D, so there's no races on
the mutable data either way unless it's `shared`... and then we need
to refer back to the thread I created months ago where `shared` is
useless and broken, and we REALLY need to fix that. (that is; `shared`
must have NO READ OR WRITE ACCESS to data members, only shared
methods, otherwise it's completely hollow)
> 4. improve code generation?
Not a lot. But this is a red-herring; D's const won't improve code
generation where it's not present in the code.
Contrary to C++, D has a much higher probability of seeing the whole
AST and not encountering opaque extern barriers, which means it would
be relatively easy for D to recognise that the const object contains
no pointers to mutable data (assessed recursively), and then enable
any such optimisations that const offers to D today.
> I know technically what it does (after all, I implemented it), but its value
> escapes me.
I mean, you speak as if `const` is a synonym for `mutable` in C++...
const things are const. It is however possible that they contain a
pointer that leads out of the const data back into the mutable world,
and that's *desirable* in a whole lot of circumstances. Take that
away, and we arrive where we are in D.
It's also easy to NOT have pointers to mutable data escaping const
objects; make them const too!
If you want to implement a semantic where the const-ness of a member
tracks the const-ness of the owner, maybe we can apply `inout` to
behave that way.
Assuming we apply rules similar to C++, it looks like:
const(S) const_s; // const instance of S
struct S
{
int* a; // becomes `int const(*)`
const(int)* b; // const(int*)
inout(int)* c; // becomes const(int*) (or immtable(int*), etc)
}
Alternatively, if const were spec-ed similar to C++ const, it would be
very easy to implement TransitiveConst!T as a tool. By any of these
means, could deploy it deliberately instead of unwillingly.
Re: DIP 1018--The Copy Constructor--Formal Review
Your DIP, and nobody else is going to do it, so it falls to me. BTW, everyone should expect the DIP process to be brutal. It has to be, we're long past the stage where we can allow misshapen stuff to get into the language. Nobody was very kind with my bottom type DIP :-) You should read the dismissal of mine and Andrei's "static if" proposal for C++! (Ironically, it was later adopted after someone else redid it, after removing one of its keystone features.)
Re: DIP 1018--The Copy Constructor--Formal Review
I agree with your point that C++ const can be used in a lot more places than D const. Absolutely true. Missing from the post, however, is an explanation of what value C++ const semantics have. How does it: 1. make code easier to understand? 2. prevent common programming bugs? 3. help with multithreaded coding problems? 4. improve code generation? I know technically what it does (after all, I implemented it), but its value escapes me.
Re: DIP 1018--The Copy Constructor--Formal Review
On Sun, Feb 24, 2019 at 4:25 PM Walter Bright via Digitalmars-d-announce wrote: > > Thanks for letting me know you're abandoning the rvalue ref DIP. It's not an "rvalue ref" DIP (which I think has confused a lot of people), it's an rvalue *by-ref* DIP. In my head, an "rvalue ref" DIP is something completely different, useful for implementing move semantics of mismatching types. Are you talking about my DIP or that other thing? > I had held off > working on it because I didn't want to duplicate efforts; we're short-staffed > enough as it is. 'abandoning's a strong word, but I don't have motivation to work on it right now. Please, be my guest!
Re: DIP 1018--The Copy Constructor--Formal Review
On Sun, Feb 24, 2019 at 4:40 PM Walter Bright via Digitalmars-d-announce wrote: > > The problem with C++ const is it only goes one level, i.e. what I call > "head-const". If you pass a T to a const parameter, anything T references > remains mutable. It's more of a suggestion than anything reliable or > enforceable. It only works if your data structures are simple aggregates, not > graphs. > > D's const has teeth. Nothing can be modified through T. If you're used to > writing code that tweaks const data under the hood, D's const will never work > for you. Yes, it means rethinking how the data and code is organized, and that > can be painful. But it is how FP works. FP offers a number of advantages, and > D's const offers a path into that. > > For example, most of DMD is written in the C++ style where functions > frequently > are written to both return some information *and* tweak the data structure. > This > does not work with const. It needs to be reorganized so that getting > information > about a data structure is separated from modifying the data structure. I've > made > such changes in a few places in DMD, and have been very pleased with the > results > - the code is much easier to understand. > > To sum up, you're quite right that you cannot write C++ style code using D > const. It hast to be in a much more FP style. If you're not accustomed with FP > style, this can be a difficult learning process. I know this from firsthand > experience :-) I agree with these facts, but your case-study is narrow, and you have to stop saying "C++ style", which it really isn't. It's very much D-style... almost all D code is written this way. It's in conflict with too many other patterns, and they're not "C++ patterns", they're very legitimate D patterns. Function pointers and delegates are often incompatible with const; practically any code with some sort of call-back behaviour, and anything that forms *any form* of traversible network where you'd like any part of it to const fails. I've never written a program that was a perfect tree. A small feature library maybe, but not a program that does anything interesting. It's great that we can write FP-ish code in D, it's particularly useful for narrow, self-contained tasks; it helps me intellectually factor some potentially complex leaf-level call-trees out of the program structure, and I appreciate when libraries take that form; it helps them have a smaller footprint in the larger complex suite. But const doesn't play into that much, and if that can't interact with normal D code, which is most code, then it's just not a useful piece of language. The proposition that everyone start writing straight-up FP code in D is unrealistic, and if they wanted that, they'd use Rust every time. People are here because they don't want to write Rust. > For me the only real annoyance with const is I often cannot use "single > assignment" style declarations with pointers: > > I.e.: > > const int* p = > p = // error, good > *p = 4; // also error, not what I wished > > This C++ const does provide, and it's good, but it's not really worth that > much. Are you serious? You can't honestly say C++ const is worthless? Especially in comparison to D's const, which is _actually_ almost completely worthless. It really doesn't make anything better, and there's a whole class of troublesome language issues that emerge from it being defined this way. The way C++ defines const is such that const can be used, and you can integrate that code with other code. I mean it seriously where I say I've tried to defend D's const for as long as I've used D, but I can't escape the plain and honest reality that D's const is not useful for almost anything practical. Even the way you describe it above is like indulging in a little bit of fetish, and I understand that, I try that every time thinking "I'm gonna get it right... this time for sure! What a cool guy I am!", but that never works out beyond a very small scope. const with a narrow scope is where it's least impactful. Then to make matters worse, `const` is a combinatorial testing nightmare; you write your code mostly without const (because conventional wisdom), and then you try and call into your lib from various contexts and it just doesn't work. You need to set-up heaps of tests to try and prove out that your code is const-robust that are very easy to miss otherwise. Then someone else tries to use your code with their code which is using const (attempting at least); I've seen lots of libraries where it would have been possible to support const, at least to some extent, but they just didn't because "don't use const", but the result is that the client of that library can't use const in their own code because the lib undermines their effort in some way. I don't like this concept that a piece of library code 'supports' const, but that's where we are. None of this is issue with C++ const, because it's defined in a way that's useful,
Re: DIP 1018--The Copy Constructor--Formal Review
On 25/02/2019 10:22 AM, Walter Bright wrote: I think we need to throw in the towel, C++'s const is right, and D's const is just wrong, and no amount of pretending that's not true will resolve the endless stream of issues. Where's the DIP to migrate to C++-style const? That is the predicate for basically every important development I've seen lately... including this one. If you want a DIP, write one! But I suggest the rvalue ref one first. We have discussed this on IRC that const needs a redesign. The problem is, without building a list of examples of where it fails we cannot really start the redesign process. But once we do, I'm in.
Re: DIP 1018--The Copy Constructor--Formal Review
On Sunday, 24 February 2019 at 21:22:33 UTC, Walter Bright wrote: On 2/24/2019 1:02 PM, Manu wrote: I mean like, my DIP was almost violently rejected, I thought it was clear what was needed to be done with it, and I thought you were going to rewrite it. Was I mistaken? Absolutely no, no. Yes! "What needs to be done" is scattered throughout forum discussions filled with incorrect assumptions, most of which were resolved needing little change, absolutely nothing that justifies a rewrite over minor amendments (the text will be 95% the same, the sentiment will be 100% the same), neither I nor Manu plan to rewrite it. Note that none of that is reflected in the official review, most (if not all) of which is wrong (and you should update it!). What is _actually_ going to happen is this will be an item on the agenda for the Foundation meeting at dconf: you will clarify the problems you have with the DIP; those problems will be discussed, evaluated and acted upon; and the DIP process will be amended to avoid the root cause of those problems.
Re: DIP 1018--The Copy Constructor--Formal Review
The problem with C++ const is it only goes one level, i.e. what I call "head-const". If you pass a T to a const parameter, anything T references remains mutable. It's more of a suggestion than anything reliable or enforceable. It only works if your data structures are simple aggregates, not graphs. D's const has teeth. Nothing can be modified through T. If you're used to writing code that tweaks const data under the hood, D's const will never work for you. Yes, it means rethinking how the data and code is organized, and that can be painful. But it is how FP works. FP offers a number of advantages, and D's const offers a path into that. For example, most of DMD is written in the C++ style where functions frequently are written to both return some information *and* tweak the data structure. This does not work with const. It needs to be reorganized so that getting information about a data structure is separated from modifying the data structure. I've made such changes in a few places in DMD, and have been very pleased with the results - the code is much easier to understand. To sum up, you're quite right that you cannot write C++ style code using D const. It hast to be in a much more FP style. If you're not accustomed with FP style, this can be a difficult learning process. I know this from firsthand experience :-) For me the only real annoyance with const is I often cannot use "single assignment" style declarations with pointers: I.e.: const int* p = p = // error, good *p = 4; // also error, not what I wished This C++ const does provide, and it's good, but it's not really worth that much.
Re: DIP 1018--The Copy Constructor--Formal Review
Thanks for letting me know you're abandoning the rvalue ref DIP. I had held off working on it because I didn't want to duplicate efforts; we're short-staffed enough as it is.
Re: DIP 1018--The Copy Constructor--Formal Review
On Sun, Feb 24, 2019 at 1:25 PM Walter Bright via Digitalmars-d-announce wrote: > > On 2/24/2019 1:02 PM, Manu wrote: > > I mean like, my DIP was almost violently rejected, > > I thought it was clear what was needed to be done with it, To be fair, initial criticism was 75% just plain wrong (like the text wasn't even read properly, with no request for clarifications), and 100% unproductive. True actionable criticisms became clear only after quite a laborious and somewhat insulting series of exchanges. > and I thought you were going to rewrite it. Was I mistaken? It's not on my short list. I don't really even wanna look at it at this point, my motivation couldn't be more depleted. There's no part of me that has any desire to re-engage that process right now. I'd encourage anybody else to take it and run though. It's still my #1 frustration... it's not getting less annoying! Incidentally, the key problems that upset people about my proposal, and probably the reason it wasn't that way from the very start are all predicated on this same `const` issue. > > but in here there's text like this: > > > > "The parameter of the copy constructor is passed by a mutable > > reference to the source object. This means that a call to the copy > > constructor may legally modify the source object:" > > > > I can't see how that could be seen in any way other than what might > > reasonably be described as "a hole large enough to drive a truck > > through"... > > What's the hole? BTW, the D copy-ctor semantics are nearly identical to that > of C++. Mutable copy-from argument is one of the same arguments people made against my DIP, except about 100x worse being a live object owned by someone else that may be undesirably mutated, rather than an expiring rvalue that nobody will ever see again. I'm mostly just amazed that the same bunch of minds that historically take such strong issue with this sort of thing can find that it's okay in this case... I can't imagine a more concerning case of this class of problem being manifest, but in this case, we've judged that it's fine? If this is acceptable now, then I think it's in order that we comb back over decades of other rejected opportunities and revisit them with this precedent. > > But anyway, that's pretty wild. I think there's a clear pattern we've > > been seeing here with practically every lifetime management DIP, and > > also in general for forever, is that D's `const` just fundamentally > > doesn't work. > > I don't see what const has to do with lifetime management. For example, it is > irrelevant to dip25 and dip1000. I say lifetime *management*; I feel copying/moving and friends are an associated part of lifetime management beyond just tracking ownership. Construction/destruction are features of lifetime management in my brain. We've had const problems with copying and constructors forever, including this DIP, and the problems that this DIP exists for to address. > > Couple this with the prevailing wisdom which is to > > recommend that people "don't use const, because you can't write > > programs and use const" > > That is true for writing C++ style code. D const is much more in line with FP > programming style. It's true for writing D style code; most D-style code is not FP code... at best, a few call-trees at the leaves of the application. The overwhelming recommendation I see posted very frequently in the forum is "don't use const", and the nature of all the articles I've read on the topic as the years progress are moving towards a more clearly stated and unashamed position of "don't use const". I understand the narrow use case where it can be applicable to FP style programming, but it comes up quite infrequently as an opportunity, and attempts are often met with a rude awakening at some point that you work far enough into your project that the fantasy of your flawless design start to break while true details of the program structure begin to emerge. Almost every attempt I've made to try and use D's const effectively has failed at some point down the path as I reach some level of complexity where the program structure has relationships that start to look like a graph. It just naturally occurs that data in a const structure may point back to the outer non-const world again, and that's totally *fine* structurally and intellectually, it's just that D can't express it. You basically have 2 options when this inevitably emerges; you sweep your code removing const from a lot of things (which sadly highlights a whole lot of wasted energy in doing so, and in your foolishly trying in the first place), or you make some HeadConst!(T) thing which casts const away, whereby you deploy UB and a quiet prayer that the compiler doesn't do anything bad. I've tried to defend D's const for a very long time, but the reality is that every sufficiently complex program I've written has seen my attempts with const fail at some level of complexity, and the forum repeats the wisdom
Re: DIP 1018--The Copy Constructor--Formal Review
On 2/24/2019 1:02 PM, Manu wrote: I mean like, my DIP was almost violently rejected, If it makes you feel any better, Razvan had to endure major rewrites of both the dip and the implementation.
Re: Beta 2.085.0
On Saturday, 16 February 2019 at 15:06:51 UTC, Martin Nowak wrote: Glad to announce the first beta for the 2.085.0 release, ♥ to the 49 contributors. http://dlang.org/download.html#dmd_beta http://dlang.org/changelog/2.085.0.html Second beta is live now.
Re: DIP 1018--The Copy Constructor--Formal Review
On 2/24/2019 1:02 PM, Manu wrote: I mean like, my DIP was almost violently rejected, I thought it was clear what was needed to be done with it, and I thought you were going to rewrite it. Was I mistaken? but in here there's text like this: "The parameter of the copy constructor is passed by a mutable reference to the source object. This means that a call to the copy constructor may legally modify the source object:" I can't see how that could be seen in any way other than what might reasonably be described as "a hole large enough to drive a truck through"... What's the hole? BTW, the D copy-ctor semantics are nearly identical to that of C++. But anyway, that's pretty wild. I think there's a clear pattern we've been seeing here with practically every lifetime management DIP, and also in general for forever, is that D's `const` just fundamentally doesn't work. I don't see what const has to do with lifetime management. For example, it is irrelevant to dip25 and dip1000. Couple this with the prevailing wisdom which is to recommend that people "don't use const, because you can't write programs and use const" That is true for writing C++ style code. D const is much more in line with FP programming style. I think we need to throw in the towel, C++'s const is right, and D's const is just wrong, and no amount of pretending that's not true will resolve the endless stream of issues. Where's the DIP to migrate to C++-style const? That is the predicate for basically every important development I've seen lately... including this one. If you want a DIP, write one! But I suggest the rvalue ref one first.
Re: DIP 1018--The Copy Constructor--Formal Review
On Sun, Feb 24, 2019 at 2:50 AM Mike Parker via Digitalmars-d-announce wrote: > > Walter and Andrei have requested the Final Review round be > dropped for DIP 1018, "The Copy Constructor", and have given it > their formal approval. They consider copy constructors a critical > feature for the language. > > Walter provided feedback on Razvan's implementation. When it > reached a state with which he was satisfied, he gave the green > light for acceptance. > > The DIP: > https://github.com/dlang/DIPs/blob/master/DIPs/accepted/DIP1018.md > > > The implementation: > https://github.com/dlang/dmd/pull/8688 I mean like, my DIP was almost violently rejected, but in here there's text like this: "The parameter of the copy constructor is passed by a mutable reference to the source object. This means that a call to the copy constructor may legally modify the source object:" I can't see how that could be seen in any way other than what might reasonably be described as "a hole large enough to drive a truck through"... But anyway, that's pretty wild. I think there's a clear pattern we've been seeing here with practically every lifetime management DIP, and also in general for forever, is that D's `const` just fundamentally doesn't work. Couple this with the prevailing wisdom which is to recommend that people "don't use const, because you can't write programs and use const" I think we need to throw in the towel, C++'s const is right, and D's const is just wrong, and no amount of pretending that's not true will resolve the endless stream of issues. Where's the DIP to migrate to C++-style const? That is the predicate for basically every important development I've seen lately... including this one.
Re: DIP 1018--The Copy Constructor--Formal Review
On Sunday, 24 February 2019 at 12:57:06 UTC, ag0aep6g wrote: On 24.02.19 11:46, Mike Parker wrote: Walter provided feedback on Razvan's implementation. When it reached a state with which he was satisfied, he gave the green light for acceptance. Sounds like it might be a "worst acceptable proposal" [1] which Andrei says the DIP process is supposed to avoid. [1] https://forum.dlang.org/post/q2ndr8$15gm$1...@digitalmars.com If I'm understanding correctly, Andrei said that about the proposals, while Walter gave feedback on the implementation, which is a little different. But yeah, the proposal was clearly fast-tracked, probably because it's needed for reference counting and better C++ integration.
Re: DIP 1018--The Copy Constructor--Formal Review
On 24.02.19 11:46, Mike Parker wrote: Walter provided feedback on Razvan's implementation. When it reached a state with which he was satisfied, he gave the green light for acceptance. Sounds like it might be a "worst acceptable proposal" [1] which Andrei says the DIP process is supposed to avoid. [1] https://forum.dlang.org/post/q2ndr8$15gm$1...@digitalmars.com
Re: DIP 1018--The Copy Constructor--Formal Review
On Sunday, 24 February 2019 at 10:46:37 UTC, Mike Parker wrote: Walter provided feedback on Razvan's implementation. When it reached a state with which he was satisfied, he gave the green light for acceptance. The DIP: https://github.com/dlang/DIPs/blob/master/DIPs/accepted/DIP1018.md Yay! Congrats to Razvan. Was this a roadblock towards reference counting, or am I confused?
DIP 1018--The Copy Constructor--Formal Review
Walter and Andrei have requested the Final Review round be dropped for DIP 1018, "The Copy Constructor", and have given it their formal approval. They consider copy constructors a critical feature for the language. Walter provided feedback on Razvan's implementation. When it reached a state with which he was satisfied, he gave the green light for acceptance. The DIP: https://github.com/dlang/DIPs/blob/master/DIPs/accepted/DIP1018.md The implementation: https://github.com/dlang/dmd/pull/8688
