Skip to content

/rust

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

`box` and `in` expressions (tracking issue for RFC 809) #22181

Closed
nikomatsakis opened this Issue Feb 11, 2015 · 3 comments

Comments

Assignees
No one assigned
Labels
B-RFC-approved C-tracking-issue T-lang
Projects
None yet
Milestone
No milestone
6 participants
@nikomatsakis @pnkfelix @aidanhs @steveklabnik @alexcrichton @Mark-Simulacrum
@nikomatsakis
Copy link
Contributor

nikomatsakis commented Feb 11, 2015 •
edited

Tracking issue for rust-lang/rfcs#809. This should be filled out with TODO items. Note that in this case there are some unsettled design questions to be resolved as well.

To do:

  • land placement-in desugaring implementation
  • land overloaded-box desugaring implementation
  • port libstd APIs to support in
  • port libstd APIs to support box
  • resolve/finalize syntax for placement-in
  • investigate improvement of inference, coercion, and cast interactions (subissues #22221, #22403, #22405)
  • improve error messages when code is rejected (#22231)

Unresolved questions:

  • best precedence for box (was #21192)

@nikomatsakis nikomatsakis referenced this issue Feb 11, 2015

Merged

overloaded-`box` and placement-`in` #809

This was referenced Feb 12, 2015

Closed
Open
Closed
Closed
Closed

@steveklabnik steveklabnik added the B-RFC-approved label Feb 13, 2015

@pnkfelix pnkfelix referenced this issue Feb 15, 2015

Merged

Pass features along during expansion #22383

bors added a commit that referenced this issue Feb 16, 2015

@bors
Auto merge of #22383 - pnkfelix:pass-features-along-during-expansion,… 
… r=huonw

Pass features along during expansion

Use the set of passed features to detect uses of feature-gated macros without the corresponding feature enabled.

Fix #22234.

----

Also, the framework this add (passing along a reference to the features in the expansion context) is a necessary precursor for landing a properly feature-gated desugaring-based overloaded-`box` and placement-`in` (#22181).

----

This is fixing a bug, but since there might be code out there that is unknowingly taking advantage of that bug, I feel obligated to mark this as a:

[breaking-change]
a108a0a

This was referenced Feb 16, 2015

Closed
Open

Manishearth added a commit to Manishearth/rust that referenced this issue Feb 17, 2015

@Manishearth
Rollup merge of rust-lang#22383 - pnkfelix:pass-features-along-during… 
…-expansion, r=huonw

 Pass features along during expansion

Use the set of passed features to detect uses of feature-gated macros without the corresponding feature enabled.

Fix rust-lang#22234.

----

Also, the framework this add (passing along a reference to the features in the expansion context) is a necessary precursor for landing a properly feature-gated desugaring-based overloaded-`box` and placement-`in` (rust-lang#22181).

----

This is fixing a bug, but since there might be code out there that is unknowingly taking advantage of that bug, I feel obligated to mark this as a:

[breaking-change]
e1f4f4b

Manishearth added a commit to Manishearth/rust that referenced this issue Feb 17, 2015

@Manishearth
Rollup merge of rust-lang#22383 - pnkfelix:pass-features-along-during… 
…-expansion, r=huonw

 Pass features along during expansion

Use the set of passed features to detect uses of feature-gated macros without the corresponding feature enabled.

Fix rust-lang#22234.

----

Also, the framework this add (passing along a reference to the features in the expansion context) is a necessary precursor for landing a properly feature-gated desugaring-based overloaded-`box` and placement-`in` (rust-lang#22181).

----

This is fixing a bug, but since there might be code out there that is unknowingly taking advantage of that bug, I feel obligated to mark this as a:

[breaking-change]
020e4e4

@pnkfelix pnkfelix referenced this issue Feb 17, 2015

Closed

Macro hygiene for patterns breaks due to static/const in scope #22462

pnkfelix added a commit to pnkfelix/rust that referenced this issue Feb 17, 2015

@pnkfelix
Test suite: Added `: Box<_>` type ascriptions to various let bindings. 
Precursor for landing rust-lang#22181.

Note that this is not *all* of the changes necessary to accommodate
Issue rust-lang#22181.  It is merely the subset of those cases where there was
already a let-binding in place that made it easy to add the necesasry
type ascription.

(For unnamed intermediate `Box` values, one must go down a different
route; `Box::new` is the option that maximizes portability, but has
potential inefficiency depending on whether the call is inlined. I may
add some unstable macro for constructing a `Box` without a call in a
future PR.)

The PR that lands rust-lang#22181 will almost certainly include further changes
to the test suite.
02839cc

pnkfelix added a commit to pnkfelix/rust that referenced this issue Feb 17, 2015

@pnkfelix
libstd: Added `: Box<_>` type ascriptions to various let bindings. 
Precursor for landing rust-lang#22181.

Note that this is not *all* of the changes necessary to accommodate
Issue rust-lang#22181.  It is merely the subset of those cases where there was
already a let-binding in place that made it easy to add the necesasry
type ascription.

(For unnamed intermediate `Box` values, one must go down a different
route; `Box::new` is the option that maximizes portability, but has
potential inefficiency depending on whether the call is inlined. I may
add some unstable macro for constructing a `Box` without a call in a
future PR.)

The PR that lands rust-lang#22181 will almost certainly include further changes
to the standard libraries.
9faf211

@pnkfelix pnkfelix referenced this issue Feb 18, 2015

Closed

Revise `lang_item` demo to something unrelated to `Box` impl #22499

bombless added a commit to bombless/rust that referenced this issue Feb 23, 2015

@bombless
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
bf2c75a

Manishearth added a commit to Manishearth/rust that referenced this issue Feb 23, 2015

@Manishearth
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

 Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
19d54b2

tshepang added a commit to tshepang/rust that referenced this issue Feb 23, 2015

@tshepang
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
ccb8ab2

tshepang added a commit to tshepang/rust that referenced this issue Feb 23, 2015

@tshepang
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
baed42f

tshepang added a commit to tshepang/rust that referenced this issue Feb 23, 2015

@tshepang
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
6dd752c

tshepang added a commit to tshepang/rust that referenced this issue Feb 23, 2015

@tshepang
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
2b1b0ee

Manishearth added a commit to Manishearth/rust that referenced this issue Mar 4, 2015

@Manishearth
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

 Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
571a94d

Manishearth added a commit to Manishearth/rust that referenced this issue Mar 4, 2015

@Manishearth
Rollup merge of rust-lang#22499 - pnkfelix:purge-demo-of-exchange-mal… 
…loc-and-free, r=steveklabnik

 Revise `lang_item` demo to something unrelated to `Box` impl

Precursor for landing overloaded-`box`, since that will decouple the `box` syntax from the exchange heap (and should eliminate the use of the two aforementioned lang items).

Instead, the new demonstration program shows a definition of the `panic_bounds_check` lang item.

(We do not have that many procedural lang-items to choose from, which is a good sign for our efforts to decouple the compiler from the runtime!)

----

Precursor for overloaded-`box` and placement-`in`; see Issue rust-lang#22181.
d23db16

@pnkfelix pnkfelix referenced this issue Jun 2, 2015

Merged

trans move_val_init expression directly into the destination address. #25959

bors added a commit that referenced this issue Jun 3, 2015

@bors
Auto merge of #25959 - pnkfelix:fsk-hack-move-val-init, r=nikomatsakis 
Hack the move_val_init intrinsic to trans directly into the destination address.

This is to remove an intermediate (and unnecessary) alloca on the stack that one otherwise suffers when using this intrinsic.

This is part of the `box` protocol work; in particular, this is meant to address the `ptr::write` codegen issues alluded to at this comment: 

  #22086 (comment)

cc #22181
fe19406

bors added a commit that referenced this issue Jun 3, 2015

@bors
Auto merge of #25959 - pnkfelix:fsk-hack-move-val-init, r=nikomatsakis 
Hack the move_val_init intrinsic to trans directly into the destination address.

This is to remove an intermediate (and unnecessary) alloca on the stack that one otherwise suffers when using this intrinsic.

This is part of the `box` protocol work; in particular, this is meant to address the `ptr::write` codegen issues alluded to at this comment: 

  #22086 (comment)

cc #22181
Loading status checks…
fe107b3

This was referenced Jun 7, 2015

Closed
Closed

bors added a commit that referenced this issue Jul 24, 2015

@bors
Auto merge of #27215 - pnkfelix:fsk-placer-take-5-just-in, r=nikomats… 
…akis

Macro desugaring of `in PLACE { BLOCK }` into "simpler" expressions following the in-development "Placer" protocol.

Includes Placer API that one can override to integrate support for `in` into one's own type.  (See [RFC 809].)

[RFC 809]: https://github.com/rust-lang/rfcs/blob/master/text/0809-box-and-in-for-stdlib.md

Part of #22181

Replaced PR #26180.

Turns on the `in PLACE { BLOCK }` syntax, while leaving in support for the old `box (PLACE) EXPR` syntax (since we need to support that at least until we have a snapshot with support for `in PLACE { BLOCK }`.

(Note that we are not 100% committed to the `in PLACE { BLOCK }` syntax.  In particular I still want to play around with some other alternatives.  Still, I want to get the fundamental framework for the protocol landed so we can play with implementing it for non `Box` types.)

----

Also, this PR leaves out support for desugaring-based `box EXPR`.  We will hopefully land that in the future, but for the short term there are type-inference issues injected by that change that we want to resolve separately.
Loading status checks…
9413a92

@alexcrichton alexcrichton added the T-lang label Aug 11, 2015

@pnkfelix pnkfelix referenced this issue Sep 24, 2015

Merged

Remove the deprecated box(PLACE) syntax. #28608

@huonw huonw referenced this issue Oct 8, 2015

Closed

Tracking issue for placement new #27779

0 of 4 tasks complete
@pnkfelix

This comment has been minimized.

Sign in to view
Copy link
Member

pnkfelix commented Jan 23, 2017

Status update: https://internals.rust-lang.org/t/lang-team-minutes-feature-status-report-placement-in-and-box/4646

@kennytm kennytm referenced this issue Feb 20, 2017

Merged

Unsized Rvalues #1909

@Mark-Simulacrum Mark-Simulacrum added C-tracking-issue and removed C-enhancement C-feature-request labels Jul 22, 2017

aidanhs added a commit to aidanhs/rust that referenced this issue Feb 18, 2018

@aidanhs
Removes all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
ec5450f

aidanhs added a commit to aidanhs/rust that referenced this issue Feb 18, 2018

@aidanhs
Removes all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
4b4f516

aidanhs added a commit to aidanhs/rust that referenced this issue Feb 18, 2018

@aidanhs
Removes all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
2d8c890

@aidanhs aidanhs referenced this issue Feb 18, 2018

Merged

Remove all unstable placement features #48333

aidanhs added a commit to aidanhs/rust that referenced this issue Feb 18, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
7be7e40

aidanhs added a commit to aidanhs/rust that referenced this issue Feb 19, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
1141310
@nikomatsakis

This comment has been minimized.

Sign in to view
Copy link
Contributor Author

nikomatsakis commented Feb 21, 2018 •
edited

FYI: @aidanhs has proposed to remove these features in #48333, and the proposal is being actively discussed. =)

aidanhs added a commit to aidanhs/rust that referenced this issue Feb 22, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
470bb76

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 27, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
d256ae3

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 27, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
3040b65

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 27, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
c71fa15

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 28, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
d997c42

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 28, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
b5947f5

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 28, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
abe792f

aidanhs added a commit to aidanhs/rust that referenced this issue Mar 29, 2018

@aidanhs
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
aabbba3

SimonSapin added a commit to aidanhs/rust that referenced this issue Apr 3, 2018

@aidanhs @SimonSapin
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
9b5859a
@aidanhs

This comment has been minimized.

Sign in to view
Copy link
Member

aidanhs commented Apr 3, 2018

Placement new is imminently about to be/has been removed as an unstable feature and the RFCs unaccepted. The approved/merged PR is at #48333 and the tracking issues were at #22181 (this issue) and #27779. Note that this does not affect box syntax.

You can find the summary comment at #27779 (comment).

Find the internals thread where you can discuss this more at https://internals.rust-lang.org/t/removal-of-all-unstable-placement-features/7223. Please add any thoughts there.

bors added a commit that referenced this issue Apr 4, 2018

@bors
Auto merge of #48333 - aidanhs:aphs-no-place-for-placement, r=nikomat… 
…sakis

Remove all unstable placement features

Closes #22181, #27779. Effectively makes the assortment of placement RFCs (rust-lang/rfcs#470, rust-lang/rfcs#809, rust-lang/rfcs#1228) 'unaccepted'. It leaves `box_syntax` and keeps the `<-` token as recognised by libsyntax.

------------------------

I don't know the correct process for unaccepting an unstable feature that was accepted as an RFC so...here's a PR.

Let me preface this by saying I'm not particularly happy about doing this (I know it'll be unpopular), but I think it's the most honest expression of how things stand today. I've been motivated by a [post on reddit](https://www.reddit.com/r/rust/comments/7wrqk2/when_will_box_and_placementin_syntax_be_stable/) which asks when these features will be stable - the features have received little RFC-style design work since the end of 2015 (~2 years ago) and leaving them in limbo confuses people who want to know where they're up to. Without additional design work that needs to happen (see the collection of unresolved questions later in this post) they can't really get stabilised, and I think that design work would be most suited to an RFC rather than (currently mostly unused) experimental features in Rust nightly.

I have my own motivations - it's very simple to 'defeat' placement in debug mode today and I don't want a placement in Rust that a) has no guarantees to work and b) has no plan for in-place serde deserialisation.

There's a quote in [1]: "Ordinarily these uncertainties might lead to the RFC being postponed. [The RFC seems like a promising direction hence we will accept since it] will thus give us immediate experience with the design and help in determining the best final solution.". I propose that there have been enough additional uncertainties raised since then that the original direction is less promising and we should be think about the problem anew.

(a historical note: the first mention of placement (under that name - uninit pointers were earlier) in an RFC AFAIK is [0] in late 2014 (pre-1.0). RFCs since then have built on this base - [1] is a comment in Feb 2015 accepting a more conservative design of the Place* traits - this is back when serde still required aster and seemed to break every other nightly! A lot has changed since then, perhaps placement should too)

------------------------

Concrete unresolved questions include:

 - making placement work in debug mode [7]
 - making placement work for serde/with fallible creation [5], [irlo2], [8]
 - trait design:
   - opting into not consuming the placer in `Placer::make_place` - [2]
   - trait proliferation - [4] (+ others in that thread)
   - fallible allocation - [3], [4] (+ others in that thread)
 - support for DSTs/unsized structs (if at all) - [1], [6]

More speculative unresolved questions include:

 - better trait design with in the context of future language features [irlo1] (Q11), [irlo3]
 - interaction between custom allocators and placement [irlo3]

[0] rust-lang/rfcs#470
[1] rust-lang/rfcs#809 (comment)
[2] rust-lang/rfcs#1286
[3] rust-lang/rfcs#1315
[4] #27779 (comment)
[5] #27779 (comment)
[6] #27779 (comment)
[7] #27779 (comment)
[8] rust-lang/rfcs#1228 (comment)
[irlo1] https://internals.rust-lang.org/t/placement-nwbi-faq-new-box-in-left-arrow/2789
[irlo2] https://internals.rust-lang.org/t/placement-nwbi-faq-new-box-in-left-arrow/2789/19
[irlo3] https://internals.rust-lang.org/t/lang-team-minutes-feature-status-report-placement-in-and-box/4646
Loading status checks…
199b7e2

@bors bors closed this in #48333 Apr 4, 2018

@aidanhs aidanhs referenced this issue Apr 6, 2018

Open

Tracking issue for box_syntax #49733

Robbepop added a commit to Robbepop/rust that referenced this issue Apr 8, 2018

@aidanhs @Robbepop
Remove all unstable placement features 
Closes rust-lang#22181, rust-lang#27779
fee7908
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.