Refactor async fn return type lowering #59286

cramertj · 2019-03-19T00:58:01Z

async fn now lowers directly to an existential type declaration
rather than reusing the impl Trait return type lowering.

As part of this, it lowers all argument-position elided lifetimes
using the in-band-lifetimes machinery, creating fresh parameter
names for each of them, using each lifetime parameter as a generic
argument to the generated existential type.

This doesn't currently successfully allow multiple
argument-position elided lifetimes since existential type
doesn't yet support multiple lifetimes where neither outlive
the other:

existential type Foo<'a, 'b>:; // error: ambiguous lifetime bound in `impl Trait`
fn foo<'a, 'b>(_: &'a u8, _: &'b u8) -> Foo<'a, 'b> { () }

This requires a separate fix.

Fix #59001
Fix #58885
Fix #55324
Fix #54974
Progress on #56238

r? @nikomatsakis

cramertj · 2019-03-19T01:01:17Z

src/test/run-pass/async-await.rs

@@ -96,14 +101,19 @@ fn async_fn_with_impl_future_named_lifetime<'a>(x: &'a u8) -> impl Future<Output
    }
 }

-async fn async_fn_with_named_lifetime_multiple_args<'a>(x: &'a u8, _y: &'a u8) -> u8 {
+async fn async_fn_multiple_args(x: &u8, _y: &u8) -> u8 {


this one still errors as discussed in the PR description.

rust-highfive · 2019-03-19T01:14:59Z

The job x86_64-gnu-llvm-6.0 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:0a77460b:start=1552957167327285107,finish=1552957244599926940,duration=77272641833
$ 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
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
Setting environment variables from .travis.yml
---

[00:03:31] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:03:31] tidy error: /checkout/src/librustc/hir/lowering.rs:5139: line longer than 100 chars
[00:03:33] some tidy checks failed
[00:03:33] 
[00:03:33] 
[00:03:33] 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"
[00:03:33] 
[00:03:33] 
[00:03:33] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:03:33] Build completed unsuccessfully in 0:00:47
[00:03:33] Build completed unsuccessfully in 0:00:47
[00:03:33] make: *** [tidy] Error 1
[00:03:33] Makefile:67: recipe for target 'tidy' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:012a6c4a
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Tue Mar 19 01:04:27 UTC 2019
---
travis_time:end:1ebb83b1:start=1552957468375444927,finish=1552957468380947856,duration=5502929
travis_fold:end:after_failure.3
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travis_time:start:017e29da
$ 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
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:1018fe60
travis_time:start:1018fe60
$ 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
travis_fold:start:after_failure.6
travis_time:start:0041fd44
$ 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)

cramertj · 2019-03-19T23:31:01Z

I've pushed an improved error message and some tests. I'd like to go ahead and land this since it fixes the below issues:

Fix #59001
Fix #58885
Fix #55324
Fix #54974
Progress on #56238

Finishing that last will require a separate change to fix existential type inference for multiple unrelated lifetime parameters.

src/librustc/hir/intravisit.rs

src/librustc/hir/lowering.rs

src/librustc/infer/opaque_types/mod.rs

nikomatsakis · 2019-03-20T15:24:10Z

This is assigned to me for review, but I would maybe prefer to re-assign to someone else, for time reasons.

@varkor or @oli-obk would either of you feel comfortable taking it?

(I am happy to consult on any "tricky questions", I just don't want to hold things up trying to do a deep dive.)

varkor · 2019-03-20T15:27:29Z

I can take this. I'll try to review fully soon.

r? @varkor

varkor

Functionally, everything looks good to me. I just have some minor nits about diagnostics and formatting.

r=me after fixing.

src/test/ui/async-fn-multiple-lifetimes.stderr

src/librustc/hir/lowering.rs

bors · 2019-03-28T12:19:34Z

☔ The latest upstream changes (presumably #59478) made this pull request unmergeable. Please resolve the merge conflicts.

async fn now lowers directly to an existential type declaration rather than reusing the `impl Trait` return type lowering. As part of this, it lowers all argument-position elided lifetimes using the in-band-lifetimes machinery, creating fresh parameter names for each of them, using each lifetime parameter as a generic argument to the generated existential type. This doesn't currently successfully allow multiple argument-position elided lifetimes since `existential type` doesn't yet support multiple lifetimes where neither outlive the other. This requires a separate fix.

cramertj · 2019-04-02T01:26:33Z

@bors r=varkor

bors · 2019-04-02T01:26:34Z

📌 Commit 749349f has been approved by varkor

bors · 2019-04-02T09:28:28Z

⌛ Testing commit 749349f with merge ec4a7ca...

@nikomatsakis

Refactor async fn return type lowering async fn now lowers directly to an existential type declaration rather than reusing the `impl Trait` return type lowering. As part of this, it lowers all argument-position elided lifetimes using the in-band-lifetimes machinery, creating fresh parameter names for each of them, using each lifetime parameter as a generic argument to the generated existential type. This doesn't currently successfully allow multiple argument-position elided lifetimes since `existential type` doesn't yet support multiple lifetimes where neither outlive the other: ```rust existential type Foo<'a, 'b>:; // error: ambiguous lifetime bound in `impl Trait` fn foo<'a, 'b>(_: &'a u8, _: &'b u8) -> Foo<'a, 'b> { () } ``` This requires a separate fix. Fix #59001 Fix #58885 Fix #55324 Fix #54974 Progress on #56238 r? @nikomatsakis

bors · 2019-04-02T10:46:10Z

💔 Test failed - checks-travis

rust-highfive · 2019-04-02T10:46:12Z

The job dist-x86_64-apple-alt 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.

[00:03:10]       Memory: 8 GB
[00:03:10]       Boot ROM Version: VMW71.00V.7581552.B64.1801142334
[00:03:10]       Apple ROM Info: [MS_VM_CERT/SHA1/27d66596a61c48dd3dc7216fd715126e33f59ae7]Welcome to the Virtual Machine
[00:03:10]       SMC Version (system): 2.8f0
[00:03:10]       Serial Number (system): VMEtJur0vJpm
[00:03:10] 
[00:03:10] hw.ncpu: 4
[00:03:10] hw.byteorder: 1234
[00:03:10] hw.memsize: 8589934592
---
Building stage2 tool cargo (x86_64-apple-darwin)
[01:07:34]  Downloading crates ...
[01:07:34] warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)
[01:07:34] warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)
[01:07:34] error: failed to download from `https://crates.io/api/v1/crates/openssl-src/111.1.0+1.1.1a/download`
[01:07:34] Caused by:
[01:07:34]   [6] Couldn't resolve host name (Could not resolve host: crates.io)
[01:07:34] command did not execute successfully: "/Users/travis/build/rust-lang/rust/build/x86_64-apple-darwin/stage0/bin/cargo" "build" "--target" "x86_64-apple-darwin" "-j" "4" "--release" "--locked" "--color" "always" "--manifest-path" "/Users/travis/build/rust-lang/rust/src/tools/cargo/Cargo.toml" "--features" "rustc-workspace-hack/all-static" "--message-format" "json"
[01:07:34] expected success, got: exit code: 101
---
travis_fold:start:after_failure.2
travis_time:start:0de31e1f
$ ls -lat $HOME/Library/Logs/DiagnosticReports/
total 0
drwx------+ 15 travis  staff  510 Jan 25  2018 ..
drwx------   2 travis  staff   68 Dec  6  2017 .
travis_fold:end:after_failure.2
travis_fold:start:after_failure.3
travis_time:start:14a854f1
$ find $HOME/Library/Logs/DiagnosticReports -type f -name '*.crash' -not -name '*.stage2-*.crash' -not -name 'com.apple.CoreSimulator.CoreSimulatorService-*.crash' -exec printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" {} \; -exec head -750 {} \; -exec echo travis_fold":"end:crashlog \; || true
$ find $HOME/Library/Logs/DiagnosticReports -type f -name '*.crash' -not -name '*.stage2-*.crash' -not -name 'com.apple.CoreSimulator.CoreSimulatorService-*.crash' -exec printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" {} \; -exec head -750 {} \; -exec echo travis_fold":"end:crashlog \; || true
travis_time:end:14a854f1:start=1554201930347887000,finish=1554201930385422000,duration=37535000
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:1cbe0e1a
$ 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
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:048d1282
travis_time:start:048d1282
$ 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
travis_fold:start:after_failure.6
travis_time:start:094f3af7
$ dmesg | grep -i kill
$ dmesg | grep -i kill
Unable to obtain kernel buffer: Operation not permitted
usage: sudo dmesg
travis_fold:end:after_failure.6

Done. Your build exited with 1.

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)

varkor · 2019-04-02T10:50:33Z

@bors retry

@nikomatsakis

Refactor async fn return type lowering async fn now lowers directly to an existential type declaration rather than reusing the `impl Trait` return type lowering. As part of this, it lowers all argument-position elided lifetimes using the in-band-lifetimes machinery, creating fresh parameter names for each of them, using each lifetime parameter as a generic argument to the generated existential type. This doesn't currently successfully allow multiple argument-position elided lifetimes since `existential type` doesn't yet support multiple lifetimes where neither outlive the other: ```rust existential type Foo<'a, 'b>:; // error: ambiguous lifetime bound in `impl Trait` fn foo<'a, 'b>(_: &'a u8, _: &'b u8) -> Foo<'a, 'b> { () } ``` This requires a separate fix. Fix rust-lang#59001 Fix rust-lang#58885 Fix rust-lang#55324 Fix rust-lang#54974 Progress on rust-lang#56238 r? @nikomatsakis

@ghost

Rollup of 8 pull requests Successful merges: - #59262 (Remove duplicated code from Iterator::{ne, lt, le, gt, ge}) - #59286 (Refactor async fn return type lowering) - #59444 (Implement useful steps_between for all integers) - #59452 (Speed up rustdoc run a bit) - #59533 (Support allocating iterators with arenas) - #59585 (Fixes for shallow borrows) - #59607 (Renames `EvalErrorKind` to `InterpError`) - #59613 (SGX target: convert a bunch of panics to aborts) Failed merges: - #59630 (Shrink `mir::Statement`.) r? @ghost

rust-highfive assigned nikomatsakis Mar 19, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 19, 2019

cramertj commented Mar 19, 2019

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cramertj force-pushed the async-fn-ret-ty branch from ccf0bcb to 37e2f8c Compare March 19, 2019 23:29

cramertj changed the title ~~[WIP] Refactor async fn return type lowering~~ Refactor async fn return type lowering Mar 19, 2019

cramertj force-pushed the async-fn-ret-ty branch from 37e2f8c to 5044c3e Compare March 19, 2019 23:32

varkor reviewed Mar 20, 2019

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rust-highfive assigned varkor and unassigned nikomatsakis Mar 20, 2019

varkor approved these changes Mar 21, 2019

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varkor added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 28, 2019

cramertj force-pushed the async-fn-ret-ty branch from 5044c3e to 749349f Compare April 2, 2019 01:26

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 2, 2019

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Apr 2, 2019

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 Apr 2, 2019

Centril mentioned this pull request Apr 2, 2019

Rollup of 8 pull requests #59632

Merged

bors merged commit 749349f into rust-lang:master Apr 2, 2019

cramertj deleted the async-fn-ret-ty branch April 2, 2019 16:18

tmandry mentioned this pull request Dec 23, 2020

Fix elided lifetimes shown as '_ on async functions #80319

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Refactor async fn return type lowering #59286

Refactor async fn return type lowering #59286

cramertj commented Mar 19, 2019 •

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Refactor async fn return type lowering #59286

Refactor async fn return type lowering #59286

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