Universes

[nikomatsakis]

This PR transitions the compiler to use universes instead of the leak-check. It is marked as [WIP] for a few reasons:

• The diagnostics at present are terrible =)
• This changes the behavior of coherence, regressing some things that used to compile

The goals of this PR at present are:

• To start getting some eyes on the code
• To do a crater run
• To see the full travis results (due to gdb 8.1 fails debuginfo tests (output changed). #52452, I am not able to run the full test suite locally anymore at present)

The first few commits in the PR are changing how evaluate treats regions. We now track whether region comparisons occurred, reverting the "staticized" query approach that @arielb1 put in. The problem with "staticized" queries is that it relied on the leak-check to get higher-ranked things correct, and we are removing the leak-check in this PR series, so that caused problems.

You can see at the end a collection of test updates. Mostly we behave the same but with atrocious diagnostics, but there are a number of cases where we used to error and now no longer do, as well as single case where we used to not error but we now do (the coherence-subtyping change).

(Note: it would be possible to do a version of leak-check that propagates universe information and recover the old behavior. I am reluctant to do so because I'd like to leave us room to get more precise -- e.g., I want to eventually handle things like exists<'a> { for<'b> { if ('a: 'b) { 'a: 'b } } } which presently the leak-check cannot cope with etc. Also because it seems more consistent to me: most folks I've talked to expect the new behavior and are surprised to learn that binding sites were so significant before when it comes to coherence. One question is, though, to what extent are people relying on this in the wild?)

[rust-highfive]

r? @eddyb

(rust_highfive has picked a reviewer for you, use r? to override)

[nikomatsakis]

r? @scalexm

[nikomatsakis]

(NB: This builds on #55305)

[rust-highfive]

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:03b94990:start=1541007419406398813,finish=1541007484369787706,duration=64963388893
$ 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
---
[00:47:25] .................................................................................................... 1200/4989
[00:47:27] .................................................................................................... 1300/4989
[00:47:30] .................................................................................................... 1400/4989
[00:47:32] ..................................................................................i................. 1500/4989
[00:47:35] ........................................................i..F........................................ 1600/4989
[00:47:42] .................................................................................................... 1800/4989
[00:47:46] ................................................................................................i... 1900/4989
[00:47:49] .................................................................................................... 2000/4989
[00:47:53] .................................................................................................... 2100/4989
---
[00:49:16] ............................................................i....................................... 4600/4989
[00:49:20] .................................................................................................... 4700/4989
[00:49:23] .................................................................................................... 4800/4989
[00:49:26] .................................................................................................... 4900/4989
, 'a) })...
[00:49:28] 8    = note: ...so that the types are compatible:
[00:49:28] 9            expected Foo<&'a isize>
[00:49:28] 10               found Foo<&isize>
[00:49:28] 
[00:49:28] The actual stderr differed from the expected stderr.
[00:49:28] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/hrtb/hrtb-perfect-forwarding/hrtb-perfect-forwarding.stderr
[00:49:28] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/hrtb/hrtb-perfect-forwarding/hrtb-perfect-forwarding.stderr
[00:49:28] To update references, rerun the tests and pass the `--bless` flag
[00:49:28] To only update this specific test, also pass `--test-args hrtb/hrtb-perfect-forwarding.rs`
[00:49:28] error: 1 errors occurred comparing output.
[00:49:28] status: exit code: 1
[00:49:28] status: exit code: 1
[00:49:28] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/hrtb/hrtb-perfect-forwarding.rs" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/hrtb/hrtb-perfect-forwarding/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/hrtb/hrtb-perfect-forwarding/auxiliary" "-A" "unused"
[00:49:28] ------------------------------------------
[00:49:28] 
[00:49:28] ------------------------------------------
[00:49:28] stderr:
[00:49:28] stderr:
[00:49:28] ------------------------------------------
[00:49:28] {"message":"cannot infer an appropriate lifetime due to conflicting requirements","code":{"code":"E0495","explanation":null},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/hrtb/hrtb-perfect-forwarding.rs","byte_start":1640,"byte_end":1656,"line_start":56,"line_end":56,"column_start":5,"column_end":21,"is_primary":true,"text":[{"text":"    foo_hrtb_bar_not(&mut t); //~ ERROR E0495","highlight_start":5,"highlight_end":21}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"first, the lifetime cannot outlive lifetime RePlaceholder(Placeholder { universe: U2, name: BrNamed(crate0:DefIndex(1:23), 'a) })...","code":null,"level":"note","spans":[],"children":[],"rendered":null},{"message":"...so that the types are compatible:\nexpected Foo<&'a isize>\n   found Foo<&isize>","code":null,"level":"note","spans":[],"children":[],"rendered":null},{"message":"but, the lifetime must be valid for the lifetime 'b as defined on the function body at 49:21...","code":null,"level":"note","spans":[{"file_name":"/checkout/src/test/ui/hrtb/hrtb-perfect-forwarding.rs","byte_start":1305,"byte_end":1307,"line_start":49,"line_end":49,"column_start":21,"column_end":23,"is_primary":true,"text":[{"text":"fn foo_hrtb_bar_not<'b,T>(mut t: T)","highlight_start":21,"highlight_end":23}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[],"rendered":null},{"message":"...so that the types are compatible:\nexpected Bar<&isize>\n   found Bar<&'b isize>","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements\n  --> /checkout/src/test/ui/hrtb/hrtb-perfect-forwarding.rs:56:5\n   |\nLL |     foo_hrtlinux-gnu/stage0-sysroot/lib/rustlib/x86_64-unknown-linux-gnu/lib
70532 ./obj/build/x86_64-unknown-linux-gnu/native
70300 ./obj/build/x86_64-unknown-linux-gnu/native/jemalloc
67720 ./src/test
67612 ./obj/build/x86_64-unknown-linux-gnu/stage1-std/x86_64-unknown-linux-gnu/release/deps

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)

[nikomatsakis]

@bors try

[bors]

⌛ Trying commit 89c5decf7f558fa6d0e04205ce54cc299bd772e2 with merge dc8b02d6f1e93f212fc39844ea688b634b4a03c7...

[bors]

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

[nikomatsakis]

@craterbot run start=master#f6e9a6e41cd9b1fb687e296b5a6d4c6ad399f862 end=try#dc8b02d6f1e93f212fc39844ea688b634b4a03c7 mode=check-only

[craterbot]

👌 Experiment pr-55517 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

[tmandry]

left some (very minor) nits on tests

[craterbot]

🚧 Experiment pr-55517 is now running on agent aws-1.

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

[craterbot]

🎉 Experiment pr-55517 is completed!
📰 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

[nikomatsakis]

Crater results all look spurious.

[rust-highfive]

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:0a5fdd58:start=1542207737343698206,finish=1542207793850600983,duration=56506902777
$ 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
---
[00:05:34]    Compiling syntax_pos v0.0.0 (/checkout/src/libsyntax_pos)
[00:05:38]    Compiling rustc_errors v0.0.0 (/checkout/src/librustc_errors)
[00:06:56]    Compiling proc_macro v0.0.0 (/checkout/src/libproc_macro)
[00:07:06]    Compiling syntax_ext v0.0.0 (/checkout/src/libsyntax_ext)
[00:07:30] error[E0599]: no method named `replace_late_bound_regions_with_fresh_var` found for type `&infer::InferCtxt<'_, '_, '_>` in the current scope
[00:07:30]      |
[00:07:30]      |
[00:07:30] 1448 |         infcx.replace_late_bound_regions_with_fresh_var(
[00:07:30]      |
[00:07:30]      = help: did you mean `replace_late_bound_regions_with_placeholders`?
[00:07:30] 
[00:07:30] 
[00:07:30] error[E0599]: no method named `predicate_must_hold` found for type `&infer::InferCtxt<'_, '_, '_>` in the current scope
[00:07:30]     |
[00:07:30]     |
[00:07:30] 561 |             infcx.predicate_must_hold(&obligation)
[00:07:30]     |
[00:07:30]     |
[00:07:30]     = help: did you mean `predicate_may_hold`?
[00:07:30] error[E0061]: this function takes 5 parameters but 7 parameters were supplied
[00:07:30]     --> librustc/traits/select.rs:3024:42
[00:07:30]      |
[00:07:30]      |
[00:07:30] 3024 |               let trait_obligations = self.impl_or_trait_obligations(
[00:07:30] ...
[00:07:30] ...
[00:07:30] 3654 | /     fn impl_or_trait_obligations(
[00:07:30] 3655 | |         &mut self,
[00:07:30] 3656 | |         cause: ObligationCause<'tcx>,
[00:07:30] ...    |
[00:07:30] 3723 | |         predicates
[00:07:30] 3724 | |     }
[00:07:30]      | |_____- defined here
---
[00:07:36] 
[00:07:36] To learn more, run the command again with --verbose.
[00:07:36] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "build" "--target" "x86_64-unknown-linux-gnu" "-j" "4" "--release" "--locked" "--color" "always" "--features" "" "--manifest-path" "/checkout/src/rustc/Cargo.toml" "--message-format" "json"
[00:07:36] expected success, got: exit code: 101
[00:07:36] thread 'main' panicked at 'cargo must succeed', bootstrap/compile.rs:1101:9
[00:07:36] travis_fold:end:stage0-rustc

[00:07:36] travis_time:end:stage0-rustc:start=1542208097061533372,finish=1542208259729488577,duration=162667955205


[00:07:36] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap build
[00:07:36] Build completed unsuccessfully in 0:03:47
[00:07:36] make: *** [all] Error 1
[00:07:36] Makefile:28: recipe for target 'all' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:14ee587d
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Wed Nov 14 15:10:59 UTC 2018
---
32392 ./src/libcompiler_buitravis_time:end:0baebe78:start=1542208260455513808,finish=1542208260467103317,duration=11589509
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:06ae7be0
$ 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:02ce8254
$ 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)

[nikomatsakis]

@matthiaskrgr are you working on fixing the toolstate change here? (I see some commits that look suggestive)

[matthiaskrgr]

Yeah, sorry about the spam.

There is a recent regression in clippy rust-lang/rust-clippy#3628 which has not been very easy to track down which prevents use from landing the fix. :/