#[must_use] on traits in stdlib #56677

aelred · 2018-12-10T14:49:38Z

Based on #55506.

Adds #[must_use] attribute to traits in the stdlib:

Iterator
Future
FnOnce
Fn
FnMut

There may be other traits that should have the attribute, but I couldn't find/think of any.

rust-highfive · 2018-12-10T14:49:48Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @sfackler (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

rust-highfive · 2018-12-10T15:04:19Z

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:139af2a0:start=1544453473013273476,finish=1544453593381890974,duration=120368617498
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#Pull-Requests-and-Security-Restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
Setting environment variables from .travis.yml
$ export IMAGE=x86_64-gnu-llvm-5.0
---

[00:03:45] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:03:45] tidy error: /checkout/src/test/compile-fail/must_use-in-stdlib-traits.rs: missing trailing newline
[00:03:46] some tidy checks failed
[00:03:46] 
[00:03:46] 
[00:03:46] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor" "--quiet"
[00:03:46] 
[00:03:46] 
[00:03:46] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:03:46] Build completed unsuccessfully in 0:00:55
[00:03:46] Build completed unsuccessfully in 0:00:55
[00:03:46] make: *** [tidy] Error 1
[00:03:46] Makefile:79: recipe for target 'tidy' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:08ec004a
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Mon Dec 10 14:57:09 UTC 2018
---
travis_time:end:01b68680:start=1544453829843660041,finish=1544453829848740622,duration=5080581
travis_fold:end:after_failure.3
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travis_time:start:36217a40
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
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travis_time:start:1a83ef09
travis_time:start:1a83ef09
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
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travis_time:start:013b87d6
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

estebank · 2018-12-10T18:34:02Z

LGTM and should probably be merged as is but I'd like to see a crater run to make sure we're not causing a lot of pain in the ecosystem by introducing these checks :)

@bors try

bors · 2018-12-10T18:34:14Z

⌛ Trying commit 3246f49 with merge aa9aa79...

#[must_use] on traits in stdlib Based on #55506. Adds `#[must_use]` attribute to traits in the stdlib: - `Iterator` - `Future` - `FnOnce` - `Fn` - `FnMut` There may be other traits that should have the attribute, but I couldn't find/think of any.

bors · 2018-12-10T20:54:17Z

☀️ Test successful - status-travis
State: approved= try=True

estebank · 2018-12-10T22:26:05Z

@craterbot run start=master#3a75e80557a103497cffbcab395a2f37061a77ea end=try#aa9aa79c3c583aab59ac9134542d60a780c35e2e mode=check-only

craterbot · 2018-12-10T22:26:07Z

👌 Experiment pr-56677 created and queued.
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2018-12-11T04:53:26Z

🚧 Experiment pr-56677 is now running on agent aws-1.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2018-12-12T19:17:02Z

🎉 Experiment pr-56677 is completed!
📊 0 regressed and 0 fixed (50551 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

estebank · 2018-12-12T21:32:47Z

@bors r+ rollup

bors · 2018-12-12T21:32:48Z

📌 Commit 3246f49 has been approved by estebank

#[must_use] on traits in stdlib Based on rust-lang#55506. Adds `#[must_use]` attribute to traits in the stdlib: - `Iterator` - `Future` - `FnOnce` - `Fn` - `FnMut` There may be other traits that should have the attribute, but I couldn't find/think of any.

Centril · 2018-12-13T00:33:25Z

src/libcore/iter/iterator.rs

@@ -98,6 +98,7 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item=()>) {}
    message="`{Self}` is not an iterator"
 )]
 #[doc(spotlight)]
+#[must_use]


This should be:

Suggested change

#[must_use]

#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]

(which can be fixed in a follow up PR)

#[must_use] on traits in stdlib Based on rust-lang#55506. Adds `#[must_use]` attribute to traits in the stdlib: - `Iterator` - `Future` - `FnOnce` - `Fn` - `FnMut` There may be other traits that should have the attribute, but I couldn't find/think of any.

scottmcm · 2018-12-15T03:57:02Z

I'm slightly worried about this.

Does this mean that v.drain(5..10); will warn, even though it's completely reasonable to ignore the iterator it produces? Does this mean that anything that returns a Range will warn if it's unused, even when the method is side-effecting?

sfackler · 2018-12-15T06:01:04Z

These only apply to trait objects, not concrete types implementing the traits I believe.

#[must_use] on traits in stdlib Based on rust-lang#55506. Adds `#[must_use]` attribute to traits in the stdlib: - `Iterator` - `Future` - `FnOnce` - `Fn` - `FnMut` There may be other traits that should have the attribute, but I couldn't find/think of any.

@ghost

Rollup of 7 pull requests Successful merges: - #56677 (#[must_use] on traits in stdlib) - #56679 (overhaul external doc attribute diagnostics) - #56682 (Update the stdsimd submodule) - #56691 (fix install broken link) - #56710 (Always set the RDRAND and RDSEED features on SGX) - #56713 (Test capacity of ZST vector) - #56841 (Add some unit tests to compiletest) Failed merges: r? @ghost

aelred added 2 commits December 10, 2018 14:45

Add test to check library traits have #[must_use] attribute

a336228

Add #[must_use] attribute to stdlib traits

ecc4ca5

rust-highfive assigned sfackler Dec 10, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Dec 10, 2018

Add trailing newline

3246f49

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 10, 2018

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Dec 12, 2018

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 12, 2018

pietroalbini mentioned this pull request Dec 12, 2018

Rollup of 17 pull requests #56757

Closed

Centril reviewed Dec 13, 2018

View reviewed changes

pietroalbini mentioned this pull request Dec 13, 2018

Rollup of 18 pull requests #56773

Closed

kennytm mentioned this pull request Dec 13, 2018

Rollup of 32 pull requests #56775

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kennytm mentioned this pull request Dec 14, 2018

Rollup of 36 pull requests #56803

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kennytm mentioned this pull request Dec 14, 2018

Rollup of 27 pull requests (second batch) #56817

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pietroalbini mentioned this pull request Dec 14, 2018

Rollup of 25 pull requests #56830

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pietroalbini mentioned this pull request Dec 15, 2018

Rollup of 7 pull requests #56846

Merged

bors merged commit 3246f49 into rust-lang:master Dec 15, 2018

varkor mentioned this pull request Dec 18, 2018

#[must_use] on traits, e.g. on Future #55506

Closed

taiki-e mentioned this pull request Jan 15, 2019

Add #[must_use] to Stream and Sink rust-lang/futures-rs#1415

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#[must_use] on traits in stdlib #56677

#[must_use] on traits in stdlib #56677

aelred commented Dec 10, 2018 •

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rust-highfive commented Dec 10, 2018

rust-highfive commented Dec 10, 2018

estebank commented Dec 10, 2018

bors commented Dec 10, 2018

bors commented Dec 10, 2018

estebank commented Dec 10, 2018

craterbot commented Dec 10, 2018

craterbot commented Dec 11, 2018

craterbot commented Dec 12, 2018

estebank commented Dec 12, 2018

bors commented Dec 12, 2018

Centril Dec 13, 2018

scottmcm commented Dec 15, 2018

sfackler commented Dec 15, 2018

	#[must_use]
	#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]

#[must_use] on traits in stdlib #56677

#[must_use] on traits in stdlib #56677

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aelred commented Dec 10, 2018 • edited Loading

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