[Issue 9665] Structure constant members can not be initialized if have opAssign

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https://issues.dlang.org/show_bug.cgi?id=9665

Walter Bright  changed:

   What|Removed |Added

   See Also||https://issues.dlang.org/sh
   ||ow_bug.cgi?id=18708

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[Issue 9665] Structure constant members can not be initialized if have opAssign

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https://issues.dlang.org/show_bug.cgi?id=9665

Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 CC||hst...@quickfur.ath.cx

--- Comment #32 from Kenji Hara k.hara...@gmail.com ---
*** Issue 9372 has been marked as a duplicate of this issue. ***

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[Issue 9665] Structure constant members can not be initialized if have opAssign

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 CC||monarchdo...@gmail.com

--- Comment #31 from Kenji Hara k.hara...@gmail.com ---
*** Issue 11952 has been marked as a duplicate of this issue. ***

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[Issue 9665] Structure constant members can not be initialized if have opAssign

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 CC||wfunct...@hotmail.com


--- Comment #30 from Kenji Hara k.hara...@gmail.com 2013-11-28 20:39:34 PST 
---
*** Issue 8118 has been marked as a duplicate of this issue. ***

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--- Comment #29 from github-bugzi...@puremagic.com 2013-11-03 20:49:18 PST ---
Commit pushed to 2.064 at https://github.com/D-Programming-Language/dlang.org

https://github.com/D-Programming-Language/dlang.org/commit/101d3a7a229b45bd97bc922f7c4df465f72d2432
Merge pull request #404 from 9rnsr/fix9665

Issue 9665 - Structure constant members can not be initialized if have opAssign

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--- Comment #28 from github-bugzi...@puremagic.com 2013-11-03 20:47:08 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/dlang.org

https://github.com/D-Programming-Language/dlang.org/commit/76bf0a581313aa6f2702f23a577f28d32a5d385f
fix Issue 9665 - Structure constant members can not be initialized if have
opAssign

Describe about field initialization behavior.

https://github.com/D-Programming-Language/dlang.org/commit/0af070ef719ef65ddd325dfb5d68b5fd987ce6aa
Merge pull request #404 from 9rnsr/fix9665

Issue 9665 - Structure constant members can not be initialized if have opAssign

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 CC||acehr...@yahoo.com


--- Comment #27 from Kenji Hara k.hara...@gmail.com 2013-10-20 02:32:33 PDT 
---
*** Issue 9732 has been marked as a duplicate of this issue. ***

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

   Keywords||pull, rejects-valid
 Blocks||11186, 11246, 10357


--- Comment #22 from Kenji Hara k.hara...@gmail.com 2013-10-14 05:58:29 PDT 
---
https://github.com/D-Programming-Language/dmd/pull/2665
https://github.com/D-Programming-Language/phobos/pull/1637

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--- Comment #23 from github-bugzi...@puremagic.com 2013-10-14 15:19:11 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/644e11ea46ac671b4a1a34a31ef5e72a6f89a2d2
fix Issue 9665 - Structure constant members can not be initialized if have
opAssign

https://github.com/D-Programming-Language/phobos/commit/5f725db1141d98c67ee3515f4edb7b43692173d7
Merge pull request #1637 from 9rnsr/fix9665

Supplemental fix for issue 9665 - Structure constant members can not be
initialized if have opAssign

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--- Comment #24 from github-bugzi...@puremagic.com 2013-10-14 15:20:11 PDT ---
Commit pushed to 2.064 at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/f5606620c5f106694a6c1ec082587d8ffba1a6c7
Merge pull request #1637 from 9rnsr/fix9665

Supplemental fix for issue 9665 - Structure constant members can not be
initialized if have opAssign

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--- Comment #26 from github-bugzi...@puremagic.com 2013-10-14 20:51:57 PDT ---
Commit pushed to 2.064 at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/44d568a7f83a43d6bbd31cbcfcf194da39a3beb7
Merge pull request #2665 from 9rnsr/fix9665

Issue 9665 - Structure constant members can not be initialized if have opAssign

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Walter Bright bugzi...@digitalmars.com changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 CC||bugzi...@digitalmars.com
 Resolution||FIXED


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--- Comment #25 from github-bugzi...@puremagic.com 2013-10-14 20:51:16 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/f8386c7eeb2518779e42e753507538188c1e3be5
fix Issue 9665 - Structure constant members can not be initialized if have
opAssign

- Change the first field assignment inside constructor to true initialization.
- Disable multiple initialization of non-mutable field, if it is once
initialized.

https://github.com/D-Programming-Language/dmd/commit/84ee9522f470cdb90031c4a8542c32e753d1462c
Merge pull request #2665 from 9rnsr/fix9665

Issue 9665 - Structure constant members can not be initialized if have opAssign

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 CC||samu...@voliacable.com


--- Comment #19 from Kenji Hara k.hara...@gmail.com 2013-10-10 05:14:26 PDT 
---
*** Issue 11204 has been marked as a duplicate of this issue. ***

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--- Comment #21 from Max Samukha samu...@voliacable.com 2013-10-10 07:10:42 
PDT ---
(In reply to comment #20)
I see there was a discussion in bug 9665. - ignore this sentence.

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--- Comment #18 from Kenji Hara k.hara...@gmail.com 2013-05-07 04:25:59 PDT 
---
(In reply to comment #17)
 So Kenji, did you fix this bug in trunk?

In local I've tried to fix this, but it had broke Phobos compilation by the
lack of proper postblit feature. Sorry...

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--- Comment #17 from Andrei Alexandrescu and...@erdani.com 2013-05-05 
19:00:14 PDT ---
So Kenji, did you fix this bug in trunk?

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--- Comment #14 from Andrei Alexandrescu and...@erdani.com 2013-03-10 
12:33:50 PDT ---
(In reply to comment #13)
 (In reply to comment #9)
  This is an insufficiency in D's design. I think we should approach this the
  same way as super() invocation and construction of qualified objects
 
 This is close to const vs postblit problem. The problem appeared due to
 unthoughtful decision to allow const objects mutation during construction. But
 it is too late now.

I disagree it's too late, seeing as I actually propose a solution. Also, this
is probably not the best forum to air criticisms about the competence and state
of mind of the language designers.

  3. This raw state lasts until super() has been called EXACTLY ONCE and each
  qualified field has been assigned to EXACTLY ONCE.
 
 I am afraid such limitation would hurt programming in cases when raw object is
 touched more than once.

I agree it would disallow some correct code, but it's not a strong limitation
to ask for exactly one initialization.

 By the way, what is about example in comment 1 when non-const opAssign stores
 mutable pointer to immutable data?

I'm not sure what you mean. What about it? This can't occur in the proposed
raw/cooked design.

  4. At that point the object has become cooked and all restrictions are
  lifted.
  
  Kenji, I recall we discussed this design in the context of const and 
  immutable
  constructors, and you were favorable to it. How about we extend the same 
  design
  for initializing qualified members in all contexts?
  
  We can reuse the same primitive flow analysis that's now used for super().
 
 I think it would be better to have special qualifier for such situation. 
 Anyway
 we implicitly have it. Problem with flow analysis is that callee may have no
 idea who is caller due to separate compilation.

I disagree. A new qualifier would complicate the language much more than a
typechecking rule for constructors. BTW the raw/cooked design is proven - it's
been already used in a number of papers and languages.

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--- Comment #15 from Maxim Fomin ma...@maxim-fomin.ru 2013-03-10 13:16:15 PDT 
---
(In reply to comment #14)
 (In reply to comment #13)
  (In reply to comment #9)
   This is an insufficiency in D's design. I think we should approach this 
   the
   same way as super() invocation and construction of qualified objects
  
  This is close to const vs postblit problem. The problem appeared due to
  unthoughtful decision to allow const objects mutation during construction. 
  But
  it is too late now.
 
 I disagree it's too late, seeing as I actually propose a solution. Also, this
 is probably not the best forum to air criticisms about the competence and 
 state
 of mind of the language designers.

The purpose was not to insult language designers but to point that affecting
one feature may break its interaction with other features. 

  By the way, what is about example in comment 1 when non-const opAssign 
  stores
  mutable pointer to immutable data?
 
 I'm not sure what you mean. What about it? This can't occur in the proposed
 raw/cooked design.
 

From what I understood, the proposal is to relax(remove temporarily) constness
of members during ctor invocation which allows code like below:

T* p;
struct T {
   void opAssign(int n) { ...; p = this; }
}
struct S {
   immutable T field;
   this(...) { field = 1;  // invoke T.opAssign (currently not allowed)
  /* now global p holds mutable pointer to immutable T object! */
   }
}

Or I misunderstood completely and you really proposing to call something like
super().

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 AssignedTo|nob...@puremagic.com|and...@erdani.com


--- Comment #1 from Kenji Hara k.hara...@gmail.com 2013-03-09 08:01:49 PST ---
This is unfixable problem, if I'm not mistaken.

Currently, compiler always considers opAssign operator overloading for all
field assignment in constructor.

struct S {
   T field;
   this(...) { field = xxx; } // If T has opAssign, it is called.
}

But for non-mutable field, opAssign invocation is not legal, because it may
break const correctness.

T* p;
struct T {
   void opAssign(int n) { ...; p = this; }
}
struct S {
   immutable T field;
   this(...) { field = 1;  // invoke T.opAssign (currently not allowed)
  /* now global p holds mutable pointer to immutable T object! */
   }
}

I have no answer for this issue... So, assigned to Andrei.

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Andrej Mitrovic andrej.mitrov...@gmail.com changed:

   What|Removed |Added

 CC||andrej.mitrov...@gmail.com


--- Comment #2 from Andrej Mitrovic andrej.mitrov...@gmail.com 2013-03-09 
09:07:15 PST ---
(In reply to comment #1)
 This is unfixable problem, if I'm not mistaken.

What if opAssign is const/inout?

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--- Comment #3 from Kenji Hara k.hara...@gmail.com 2013-03-09 09:14:18 PST ---
(In reply to comment #2)
 (In reply to comment #1)
  This is unfixable problem, if I'm not mistaken.
 
 What if opAssign is const/inout?

It would be invoked, but you cannot do any meaningful operation in it.

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--- Comment #6 from Maksim Zholudev maxim...@gmail.com 2013-03-09 09:47:58 
PST ---
(In reply to comment #1)
 But for non-mutable field, opAssign invocation is not legal, because it may
 break const correctness.
 
 T* p;
 struct T {
void opAssign(int n) { ...; p = this; }
 }
 struct S {
immutable T field;
this(...) { field = 1;  // invoke T.opAssign (currently not allowed)
   /* now global p holds mutable pointer to immutable T object! */
}
 }

Is there any way to break const correctness if opAssign is pure?

If not, then changes should be allowed for pure opAssign (e.g. with implicit
cast field to mutable).

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--- Comment #7 from Kenji Hara k.hara...@gmail.com 2013-03-09 10:29:11 PST ---
(In reply to comment #5)
[snip]

To enforce breaking type system by language users is not good at all.

When talking about language semantics, unsafe operation like cast must not
appear. Language user can break type system explicitly, but compiler must not
do it.

(In reply to comment #6)
 Is there any way to break const correctness if opAssign is pure?

'pure' attribute does not affect constancy.

 If not, then changes should be allowed for pure opAssign (e.g. with implicit
 cast field to mutable).

opAssign should modify its 'this' object for the meaningful operation, but
mutable method cannot call on non-const object, even inside constructor. So
this problem is unfixable.

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Andrei Alexandrescu and...@erdani.com changed:

   What|Removed |Added

 CC||and...@erdani.com


--- Comment #10 from Andrei Alexandrescu and...@erdani.com 2013-03-09 
17:43:08 PST ---
Assigned to Kenji :o).

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--- Comment #9 from Andrei Alexandrescu and...@erdani.com 2013-03-09 17:42:11 
PST ---
This is an insufficiency in D's design. I think we should approach this the
same way as super() invocation and construction of qualified objects:

1. When a constructor is entered, the object is in a raw state.

2. While in this raw state, the object is not considered initialized so it
can't be passed to functions etc. Its const/immutable members (be they by their
own qualifier or propagated from the object) are also raw and can't be passed
out.

3. This raw state lasts until super() has been called EXACTLY ONCE and each
qualified field has been assigned to EXACTLY ONCE.

4. At that point the object has become cooked and all restrictions are
lifted.

Kenji, I recall we discussed this design in the context of const and immutable
constructors, and you were favorable to it. How about we extend the same design
for initializing qualified members in all contexts?

We can reuse the same primitive flow analysis that's now used for super().

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--- Comment #12 from Andrei Alexandrescu and...@erdani.com 2013-03-09 
18:32:32 PST ---
@Kenji: that's exactly right. Just in case it isn't obvious, that only
assignment for qualified fields while in raw state is not an opAssign call,
it's a constructor call.

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