Improve parsing diagnostic for negative supertrait bounds #57364

hdhoang · 2019-01-06T00:32:01Z

src/libsyntax/ast.rs

src/librustc_passes/ast_validation.rs

rust-highfive · 2019-01-06T14:45:03Z

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.

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travis_time:end:0ec3f578:start=1546782125819050653,finish=1546782196239804965,duration=70420754312
$ 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-6.0
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[01:01:31] - LL | trait Tr4: !Sized + !Send + Copy + !Sync + !Unpin {} //~ ERROR negative trait bounds are not supported
[01:01:31] -    |                                  --^^^^^
[01:01:31] + LL | trait Tr4: !Sized + Copy + !Sync + !Unpin {} //~ ERROR negative trait bounds are not supported
[01:01:31] +    |                                  --^^^^^^
[01:01:31] 47    |                                  help: remove this trait bound
[01:01:31] 48 
[01:01:31] 
[01:01:31] 49 error: negative trait bounds are not supported
[01:01:31] 49 error: negative trait bounds are not supported
[01:01:31] -   --> $DIR/issue-33418.rs:6:44
[01:01:31] -    |
[01:01:31] - LL | trait Tr4: !Sized + !Send + Copy + !Sync + !Unpin {} //~ ERROR negative trait bounds are not supported
[01:01:31] -    |                                          --^^^^^^
[01:01:31] -    |                                          help: remove this trait bound
[01:01:31] - 
[01:01:31] - error: negative trait bounds are not supported
[01:01:31] 58   --> $DIR/issue-33418.rs:7:12
[01:01:31] 58   --> $DIR/issue-33418.rs:7:12
[01:01:31] 59    |
[01:01:31] 60 LL | trait Tr5: !Sized + !Send {} //~ ERROR negative trait bounds are not supported
[01:01:31] 70    |                   |
[01:01:31] 71    |                   help: remove this trait bound
[01:01:31] 72 
[01:01:31] - error: aborting due to 9 previous errors
---
[01:01:31] 
[01:01:31] thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:495:22
[01:01:31] 
[01:01:31] 
[01:01:31] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-6.0/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "6.0.0\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/travis_time:end:2a9fb0c4:start=1546782205172551672,finish=1546785897059313420,duration=3691886761748
travis_time:start:03060326
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Sun Jan  6 14:44:57 UTC 2019
Sun, 06 Jan 2019 14:44:57 GMT

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

It seems like the tests are currently broken. Added an alternative way of getting the suggestion span.

src/libsyntax/parse/parser.rs

stokhos · 2019-01-14T04:39:07Z

Ping from triage @hdhoang Have you been able to make any progress on this?

hdhoang · 2019-01-14T05:48:53Z

thank you, I have a rough outline of the necessary flow inside the loop. I will describe most of it later while working it out locally.

hdhoang · 2019-01-14T23:34:20Z

I have pushed a WIP flow for review.

Firstly, I have renamed the supertraits in tests to make talking about them easier.

On to the parser, to pass the colon span into the loop, I have added a colon_span argument to parse_generic_bounds/parse_generic_bounds_common, then passing DUMMY_SP at irrelevant callsites. The name isn't descriptive, but hopefully using a dummy span elsewhere makes it clear.

Next, I have implemented your last_plus_span flow, and created a flag to track whether we need to promote a plus to a colon to keep the code valid. I temporarily used struct_span_err here, but I think a warning/note/help message hanging on to last_plus_span is more appropriate. I will find a more suitable macro for that, and a clearer message for "will become the first one".

estebank

The output looks superb.

I think that we can iterate on the changes to parse_generic_bounds_common, as you're using a DUMMY_SP in some cases. I think that replacing that with None would be safer, and just avoid giving any suggestion if colon_span isn't Some(sp), just a help line similar to what we have now.

You can see how I handled a similar suggestion case in 28ea03e, but that one was more self contained.

src/libsyntax/parse/parser.rs

hdhoang · 2019-01-16T22:05:31Z

thanks! I intend to update this weekend, and see how it goes

hdhoang · 2019-01-19T14:41:16Z

hopefully I have addressed your review correctly. I have also downgraded the colon suggestion to a warning, since it's due to rustfix, not the original code

hdhoang · 2019-01-23T12:56:33Z

ping @estebank, have you had a chance chance to look at this?

estebank

Apologies for the delay. Some suggestions inline. Let me know what you think.

src/libsyntax/parse/parser.rs

estebank · 2019-01-23T18:32:46Z

src/libsyntax/parse/parser.rs

+                                "".into(),
+                                Applicability::MachineApplicable);
+                        } else {
+                            err.help("remove this trait bound");


If the other comment is implemented, this is the branch where you would have to account for the trailing + span instead, and suggest the removal of it, instead of in the warning.

src/test/ui/parser/issue-33418.stderr

hdhoang · 2019-02-02T14:37:16Z

src/test/ui/parser/issue-33418.stderr

+help: remove the trait bound
+   |
+LL | trait Tr3 + SuperB {} //~ ERROR negative trait bounds are not supported
+   |         --


These help messages come out nonsensical, but the code suggestions apply correctly. Is this okay?

This is a shame, we should try to make the suggestion more readable by showing the final code in a single step, instead of applying multiple changes at the same time. In this case it should be something like

error: negative trait bounds are not supported --> $DIR/issue-33418.rs:5:10 | LL | trait Tr3: !SuperA + SuperB {} //~ ERROR negative trait bounds are not supported | ^^^^^^^^^ help: remove the trait bound | LL | trait Tr3: SuperB {} //~ ERROR negative trait bounds are not supported | --

src/libsyntax/parse/parser.rs

hdhoang · 2019-02-03T23:55:48Z

I have reconstructed a new bound list from the parsed bounds, unfortunately this will also delete linebreaks and compiletest`s comment. However I hope this method have minimal impact on the happy path.

hdhoang · 2019-02-09T14:40:07Z

hi @estebank, how do you feel about the current approach?

estebank · 2019-02-11T20:13:32Z

@hdhoang I've been away for the past week. I'll try to review today.

bors · 2019-02-12T22:14:51Z

☔ The latest upstream changes (presumably #58341) made this pull request unmergeable. Please resolve the merge conflicts.

hdhoang · 2019-02-13T04:22:56Z

I have resolved the conflict locally, but still would like to wait to rebase & make use of #58296 before pushing

hdhoang · 2019-02-17T09:15:38Z

Using span_suggestion_hidden gave the same output as span_suggestion_short, so I have skipped out on that change and only fixed the conflict.

estebank · 2019-02-20T23:47:30Z

@bors r+

bors · 2019-02-20T23:47:32Z

📌 Commit a55f1c3da60797b5c705ef34433a1d3414f99bf6 has been approved by estebank

hdhoang · 2019-02-22T10:09:49Z

Looks to be a network failure, please retry.

ljedrz · 2019-02-22T10:12:34Z

@bors retry

bors · 2019-02-22T10:12:35Z

@ljedrz: 🔑 Insufficient privileges: not in try users

ljedrz · 2019-02-22T10:15:03Z

Oops, it seems that my try privileges haven't been deployed yet.

kennytm · 2019-02-22T14:23:10Z

@bors retry

bors · 2019-02-23T00:18:50Z

☔ The latest upstream changes (presumably #58644) made this pull request unmergeable. Please resolve the merge conflicts.

hdhoang · 2019-02-23T00:20:29Z

I'll get on this

hdhoang · 2019-02-23T08:56:51Z

hi, this is good to go again. please ask @bors to retry.

ljedrz · 2019-02-23T09:16:26Z

Ok, let's try again ^^.

@bors retry

bors · 2019-02-23T09:16:26Z

@ljedrz: 🔑 Insufficient privileges: not in try users

kennytm · 2019-02-23T09:19:48Z

After push to a PR it can't simply be retried, it must be r+'ed again.

@bors r=estebank

bors · 2019-02-23T09:21:42Z

📌 Commit 7cfddfb has been approved by estebank

@estebank

…tebank Improve parsing diagnostic for negative supertrait bounds closes rust-lang#33418 r? @estebank

@estebank

…tebank Improve parsing diagnostic for negative supertrait bounds closes rust-lang#33418 r? @estebank

@ghost

Rollup of 6 pull requests Successful merges: - #57364 (Improve parsing diagnostic for negative supertrait bounds) - #58183 (Clarify guarantees for `Box` allocation) - #58442 (Simplify the unix `Weak` functionality) - #58454 (Refactor Windows stdio and remove stdin double buffering ) - #58511 (Const to op simplification) - #58642 (rustdoc: support methods on primitives in intra-doc links) Failed merges: r? @ghost

hdhoang · 2019-02-24T10:15:55Z

thanks to everyone for guidance!

rust-highfive assigned estebank Jan 6, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 6, 2019

petrochenkov reviewed Jan 6, 2019

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hdhoang commented Jan 6, 2019

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estebank requested changes Jan 7, 2019

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estebank 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 Jan 7, 2019

estebank reviewed Jan 14, 2019

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