Make Copy a subtrait of Clone #23860

nikomatsakis · Mar 30, 2015

Logically, Copy: Clone makes sense, since Copy basically means "I can clone this with just memcpy". This also means that one can start out with a Copy bound and relax it to a Clone bound.

This is a [breaking-change] because one must change #[derive(Copy)] to #[derive(Copy,Clone)]. In some cases, deriving doesn't create a proper clone impl (notably around fixed-length arrays), in which case you should write one by hand. Because the type in question is Copy, this is very simple:

impl Clone for Foo { fn clone(&self) -> Foo { *self } }

Fixes #23790.

r? @aturon (stabilization issue)

pnkfelix · Mar 30, 2015

pnkfelix reviewed Mar 30, 2015

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pnkfelix · Mar 30, 2015

src/test/run-pass/guards-not-exhaustive.rs

@@ -8,10 +8,18 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.

+<<<<<<< HEAD


this can't be right.

I would guess not

alexcrichton · Mar 30, 2015

alexcrichton reviewed Mar 30, 2015

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alexcrichton · Mar 30, 2015

src/liblibc/lib.rs

@@ -227,7 +227,7 @@ pub mod types {
                pub type rlim_t = u64;

                #[repr(C)]
-                #[derive(Copy)] pub struct glob_t {
+                #[derive(Copy, Clone)] pub struct glob_t {


Hm, the fallout in FFI types is... somewhat unfortunate!

@alexcrichton why? (that is, why is this any more unfortunate than any other fallout?)

seems like this will be a lot less painful for everyone if we made #[derive(Copy)] imply #[derive(Clone)]...

I personally prefer to not see inherent methods and trait implementations directly on FFI types but rather on appropriate wrappers, so this is forcing the addition of a trait implementation on FFI types that want to also be Copy. Although others may differ on that opinion!

I do agree that inferred derive would be nice.

I see. Seems like a minor thing to me though. You can still avoid trait impls beyond Copy/Clone if you choose.

aturon · Mar 30, 2015

r=me once bad merge is resolved.

bors · Mar 30, 2015

☔️ The latest upstream changes (presumably #23673) made this pull request unmergeable. Please resolve the merge conflicts.

nikomatsakis · Mar 30, 2015

Created a discuss thread about this PR http://internals.rust-lang.org/t/making-copy-a-subtrait-of-clone-pr-23860/1777

theemathas · Mar 31, 2015

I have always assumed that Copy was not a subtrait of Clone because of &T.

Turns out that &T is both Copy and Clone, after all.

👍 😃

nikomatsakis · Mar 31, 2015

@bors r=aturon 32b6ec6

nikomatsakis · Mar 31, 2015

oh, needs merge.

bors · Mar 31, 2015

☔️ The latest upstream changes (presumably #23549) made this pull request unmergeable. Please resolve the merge conflicts.

nikomatsakis · Apr 1, 2015

@bors r= aturon 1b5ac16

bors · Apr 1, 2015

📌 Commit 1b5ac16 has been approved by ``

nikomatsakis · Apr 1, 2015

@bors r=aturon 1b5ac16

nikomatsakis · Apr 1, 2015

@bors r=aturon c35c468

Manishearth · Apr 1, 2015

Would this bloat crate size for crates that derive Copy on exported types but not Clone?

I'm also a bit concerned if this affects #![no_std] since Copy is a lang item.

nikomatsakis · Apr 1, 2015

@bors r=aturon 943729f

nikomatsakis · Apr 1, 2015

@Manishearth presumably this will affect crate sizes, specifically metadata. As for #![no_std], avoiding the core crate feels to me like it's kind of "extra unstable" -- you're just asking for trouble, given the number of lang items and intrinsics that are in there.

Bottom line for me though is that making Copy: Clone is really the right call for the language in multiple ways, whereas problems of binary size etc feel like artifacts of current implementation.

Manishearth · Apr 1, 2015

http://buildbot.rust-lang.org/builders/auto-win-32-nopt-t/builds/3983 ?

nikomatsakis · Apr 1, 2015

@Manishearth that should be fixed by the most recent push.

bors · Apr 2, 2015

☔️ The latest upstream changes (presumably #23955) made this pull request unmergeable. Please resolve the merge conflicts.

alexcrichton · Apr 2, 2015

gah I missed this in the rollup!

rust-highfive assigned aturon Mar 30, 2015

nikomatsakis referenced this pull request Mar 30, 2015
Closed
make Copy: Clone #23790

nikomatsakis force-pushed the nikomatsakis:copy-requires-clone branch from e340206 to a608750 Mar 30, 2015

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erickt referenced this pull request Mar 31, 2015
Closed
Make #[derive(Copy, Eq, Ord)] imply #[derive(Clone, PartialEq, PartialOrd)] #23905

nikomatsakis force-pushed the nikomatsakis:copy-requires-clone branch from a758cf5 to 1b5ac16 Apr 1, 2015

nikomatsakis added some commits Mar 26, 2015

Make the trait Copy extend Clone.

c4edd0c

Fallout in tests

890ed5c

Fallout out rustc

d9530c0

Fallout in libsyntax

49b76a0

Fallout in public-facing and semi-public-facing libs

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c35c468

nikomatsakis force-pushed the nikomatsakis:copy-requires-clone branch from 1b5ac16 to c35c468 Apr 1, 2015

Missing imports

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943729f

Manishearth referenced this pull request Apr 1, 2015
Closed
Rollup of 9 pull requests #23946

bors added a commit that referenced this pull request Apr 1, 2015

Auto merge of #23946 - Manishearth:rollup, r=Manishearth
- Successful merges: #23066, #23860, #23895, #23924, #23925, #23927, #23932, #23933, #23942 - Failed merges: #23867, #23938

ed3b7b3

bors added a commit that referenced this pull request Apr 1, 2015

Auto merge of #23946 - Manishearth:rollup, r=Manishearth
- Successful merges: #23066, #23860, #23895, #23924, #23925, #23927, #23932, #23933, #23942 - Failed merges: #23867, #23938

9f18f80

Fix enum timezone across all platforms.

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4496433

alexcrichton added a commit to alexcrichton/rust that referenced this pull request Apr 2, 2015

rollup merge of rust-lang#23860: nikomatsakis/copy-requires-clone
Conflicts: src/test/compile-fail/coherence-impls-copy.rs

f92e7ab

bors merged commit 4496433 into rust-lang:master Apr 2, 2015
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semarie referenced this pull request Apr 2, 2015
Merged
libc: unbreak severals os/platform #23967

alexcrichton referenced this pull request Apr 2, 2015
Closed
Automatically derive {Clone,PartialEq,PartialOrd} when {Copy,Eq,Ord} are derived #1028

andersk added a commit to andersk/image-rs that referenced this pull request Apr 3, 2015

Derive Clone when deriving Copy
As per rust-lang/rust#23860, Copy now extends Clone. Signed-off-by: Anders Kaseorg <andersk@mit.edu>

ef044ab

CraZySacX referenced this pull request Apr 3, 2015
Merged
Fd ist now RawFd (rustup) #92

andersk added a commit to andersk/image-rs that referenced this pull request Apr 3, 2015

Derive Clone when deriving Copy
As per rust-lang/rust#23860, Copy now extends Clone. Signed-off-by: Anders Kaseorg <andersk@mit.edu>

ea58de3

DaGenix added a commit to DaGenix/rust-crypto that referenced this pull request Apr 4, 2015

Merge pull request #290 from rustyhorde/master
Fixes for change introduced by rust-lang/rust#23860

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734248d

zmack referenced this pull request Apr 5, 2015
Closed
Compatibility with rust latest #94

justinlatimer referenced this pull request Apr 7, 2015
Merged
Derive Clone trait for Stopwatch #3

jooert referenced this pull request Apr 29, 2015
Closed
Update code to compile with latest rustc. #6

0xbrt added a commit to 0xbrt/rust-alsa that referenced this pull request Jun 17, 2015

Derive `Clone` for copyable types
Copy is a subtrait of Clone (see rust-lang/rust#23860), meaning memcopyable types must derive from Clone as well as Copy.

5de2eb5

mitaa referenced this pull request Jul 13, 2015
Closed
Ownership error masks missing implementation of trait #27009

nikomatsakis deleted the nikomatsakis:copy-requires-clone branch Mar 30, 2016

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Make Copy a subtrait of Clone #23860

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bors merged commit `4496433` into rust-lang:master Apr 2, 2015
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