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Refactor async fn return type lowering #59286

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merged 1 commit into from Apr 2, 2019

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commented Mar 19, 2019

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

@@ -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 {

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this one still errors as discussed in the PR description.

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commented Mar 19, 2019

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
travis_fold:start:after_failure.4
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 cramertj force-pushed the cramertj:async-fn-ret-ty branch from ccf0bcb to 37e2f8c Mar 19, 2019

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commented Mar 19, 2019

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.

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

@cramertj cramertj force-pushed the cramertj:async-fn-ret-ty branch from 37e2f8c to 5044c3e Mar 19, 2019

Show resolved Hide resolved src/librustc/hir/intravisit.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/infer/opaque_types/mod.rs Outdated
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commented Mar 20, 2019

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.)

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commented Mar 20, 2019

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

r? @varkor

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

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varkor approved these changes Mar 21, 2019

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

r=me after fixing.

Show resolved Hide resolved src/test/ui/async-fn-multiple-lifetimes.stderr Outdated
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Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
Show resolved Hide resolved src/librustc/hir/lowering.rs Outdated
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commented Mar 28, 2019

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

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. This requires a separate fix.

@cramertj cramertj force-pushed the cramertj:async-fn-ret-ty branch from 5044c3e to 749349f Apr 2, 2019

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commented Apr 2, 2019

@bors r=varkor

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commented Apr 2, 2019

📌 Commit 749349f has been approved by varkor

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commented Apr 2, 2019

⌛️ Testing commit 749349f with merge ec4a7ca...

bors added a commit that referenced this pull request Apr 2, 2019

Auto merge of #59286 - cramertj:async-fn-ret-ty, r=varkor
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
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commented Apr 2, 2019

💔 Test failed - checks-travis

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commented Apr 2, 2019

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)

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commented Apr 2, 2019

@bors retry

Centril added a commit to Centril/rust that referenced this pull request Apr 2, 2019

Rollup merge of rust-lang#59286 - cramertj:async-fn-ret-ty, r=varkor
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

@Centril Centril referenced this pull request Apr 2, 2019

Merged

Rollup of 8 pull requests #59632

bors added a commit that referenced this pull request Apr 2, 2019

Auto merge of #59632 - Centril:rollup, r=Centril
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

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

1 check failed

homu Test failed
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@cramertj cramertj deleted the cramertj:async-fn-ret-ty branch Apr 2, 2019

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