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Allow Trait inheritance with cycles on associated types take 2 #80732

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merged 4 commits into from
Feb 9, 2021

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spastorino
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This reverts the revert of #79209 and fixes the ICEs that's occasioned by that PR exposing some problems that are addressed in #80648 and #79811.
For easier review I'd say, check only the last commit, the first one is just a revert of the revert of #79209 which was already approved.

This also could be considered part or the actual fix of #79560 but I guess for that to be closed and fixed completely we would need to land #80648 and #79811 too.

r? @nikomatsakis
cc @Aaron1011

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 5, 2021
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jyn514 commented Jan 5, 2021

@bors try

So people can easily install this with https://github.com/kennytm/rustup-toolchain-install-master (#79560 (comment))

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bors commented Jan 5, 2021

⌛ Trying commit 958a97b56a7cfdaa35b032fbaa49385c5d08dfe8 with merge c963187c6f959417cbb13a33e9eaea4607696fc4...

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@jyn514 yeah that's great. I've force pushed but all I've changed there is the test I've added to be check-pass instead of build-pass, so don't worry about that.

@camelid camelid added A-trait-system Area: Trait system T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jan 6, 2021
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spastorino commented Jan 6, 2021

@nikomatsakis, now that this is tested, should be ready for review/merge.

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nikomatsakis commented Jan 16, 2021

Just to make sure I understand the situation:

  • changing from Ident to Symbol basically works around the hygiene problems we encountered
  • but once Add disambiugator to ExpnData #79811 lands, we wouldn't have had those problems in the first place?

Is there a test for the new ICEs we encountered? I couldn't quite tell.

If all that is correct, r=me.

@bors delegate+

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bors commented Jan 16, 2021

✌️ @spastorino can now approve this pull request

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@nikomatsakis what you've said is correct. About the test check the second commit (the one that's not the revert) and at the end you'll find the test.

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@bors r=nikomatsakis

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bors commented Jan 16, 2021

📌 Commit 455a0e1 has been approved by nikomatsakis

@bors 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 Jan 16, 2021
m-ou-se added a commit to m-ou-se/rust that referenced this pull request Jan 16, 2021
… r=nikomatsakis

Allow Trait inheritance with cycles on associated types take 2

This reverts the revert of rust-lang#79209 and fixes the ICEs that's occasioned by that PR exposing some problems that are addressed in rust-lang#80648 and rust-lang#79811.
For easier review I'd say, check only the last commit, the first one is just a revert of the revert of rust-lang#79209 which was already approved.

This also could be considered part or the actual fix of rust-lang#79560 but I guess for that to be closed and fixed completely we would need to land rust-lang#80648 and rust-lang#79811 too.

r? `@nikomatsakis`
cc `@Aaron1011`
@lnicola lnicola mentioned this pull request Jan 17, 2021
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lnicola commented Jan 17, 2021

@jyn514 what commit should I use with rustup-toolchain-install-master? Neither 03c0e58 nor 455a0e1 work.

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m-ou-se commented Jan 17, 2021

@lnicola That only works for commits that have been built by bors. Try the commits mentioned in #80732 (comment).

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lnicola commented Jan 17, 2021

@spastorino this introduces an error while compiling salsa:

error[E0221]: ambiguous associated type `Group` in bounds of `Q`
   --> src/interned.rs:466:57
    |
466 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<Q::Group>>::group_storage(db);
    |                                                         ^^^^^^^^ ambiguous associated type `Group`
    | 
   ::: src/lib.rs:431:5
    |
431 |     type Group: plumbing::QueryGroup<GroupStorage = Self::GroupStorage>;
    |     --------------------------------------------------------------------
    |     |
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |
help: use fully qualified syntax to disambiguate
    |
466 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: use fully qualified syntax to disambiguate
    |
466 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0221]: ambiguous associated type `Group` in bounds of `Q`
   --> src/interned.rs:478:57
    |
478 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<Q::Group>>::group_storage(db);
    |                                                         ^^^^^^^^ ambiguous associated type `Group`
    | 
   ::: src/lib.rs:431:5
    |
431 |     type Group: plumbing::QueryGroup<GroupStorage = Self::GroupStorage>;
    |     --------------------------------------------------------------------
    |     |
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |
help: use fully qualified syntax to disambiguate
    |
478 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: use fully qualified syntax to disambiguate
    |
478 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0221]: ambiguous associated type `Group` in bounds of `Q`
   --> src/interned.rs:490:57
    |
490 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<Q::Group>>::group_storage(db);
    |                                                         ^^^^^^^^ ambiguous associated type `Group`
    | 
   ::: src/lib.rs:431:5
    |
431 |     type Group: plumbing::QueryGroup<GroupStorage = Self::GroupStorage>;
    |     --------------------------------------------------------------------
    |     |
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |
help: use fully qualified syntax to disambiguate
    |
490 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: use fully qualified syntax to disambiguate
    |
490 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0221]: ambiguous associated type `Group` in bounds of `Q`
   --> src/interned.rs:512:57
    |
512 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<Q::Group>>::group_storage(db);
    |                                                         ^^^^^^^^ ambiguous associated type `Group`
    | 
   ::: src/lib.rs:431:5
    |
431 |     type Group: plumbing::QueryGroup<GroupStorage = Self::GroupStorage>;
    |     --------------------------------------------------------------------
    |     |
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |     ambiguous `Group` from `for<'d> QueryDb<'d>`
    |
help: use fully qualified syntax to disambiguate
    |
512 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: use fully qualified syntax to disambiguate
    |
512 |             <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
    |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0221`.
error: could not compile `salsa`

Do you know if that is intended? The two suggestions seem identical. Or is it a single suggestion printed twice?

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m-ou-se commented Jan 17, 2021

@bors r-

That failed in this rollup: #81102 (comment)

(Thanks @lnicola for figuring it out!)

@bors bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jan 17, 2021
@spastorino spastorino force-pushed the trait-inheritance-self2 branch 2 times, most recently from 149e8ab to fae509c Compare February 2, 2021 20:56
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Have just changed back to Ident given that @Aaron1011 has fixed the original underlying issue.

@lnicola can you tell me how to reproduce the salsa issue? or better said, do you have an MCVE for it?.

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lnicola commented Feb 3, 2021

@spastorino try this, it was a pain to minimize:

pub struct LookupInternedStorage;

impl<Q> QueryStorageOps<Q> for LookupInternedStorage
where
    Q: Query,
    for<'d> Q: QueryDb<'d>,
{
    fn fmt_index(&self, db: &<Q as QueryDb<'_>>::DynDb) {
        <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<Q::Group>>::group_storage(db);
    }
}

pub trait HasQueryGroup<G>
{
    fn group_storage(&self);
}

pub trait QueryStorageOps<Q>
where
    Q: Query,
{
    fn fmt_index(&self, db: &<Q as QueryDb<'_>>::DynDb);
}

pub trait QueryDb<'d> {
    type DynDb: HasQueryGroup<Self::Group> + 'd;
    type Group;
}

pub trait Query: for<'d> QueryDb<'d> {
}
$ cargo +c963187c6f959417cbb13a33e9eaea4607696fc4 build
   Compiling salsa-min v0.1.0 (/home/grayshade/salsa-min)
error[E0221]: ambiguous associated type `Group` in bounds of `Q`
  --> src/main.rs:9:53
   |
9  |         <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<Q::Group>>::group_storage(db);
   |                                                     ^^^^^^^^ ambiguous associated type `Group`
...
30 |     type Group;
   |     -----------
   |     |
   |     ambiguous `Group` from `for<'d> QueryDb<'d>`
   |     ambiguous `Group` from `for<'d> QueryDb<'d>`
   |
help: use fully qualified syntax to disambiguate
   |
9  |         <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
   |                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: use fully qualified syntax to disambiguate
   |
9  |         <<Q as QueryDb<'_>>::DynDb as HasQueryGroup<<Q as for<'d> QueryDb<'d>>::Group>>::group_storage(db);
   |                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0221`.
error: could not compile `salsa-min`

To learn more, run the command again with --verbose.

$ cargo +stable check
    Finished dev [unoptimized + debuginfo] target(s) in 0.19s

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bors commented Feb 5, 2021

☔ The latest upstream changes (presumably #81784) made this pull request unmergeable. Please resolve the merge conflicts.

@rust-log-analyzer

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…itance-self, r=Mark-Simulacrum"

This reverts commit b4def89, reversing
changes made to 7dc1e85.
An ICE happened when certain code is compiled in incremental compilation
mode and there are two `Ident`s that have the same `StableHash` value
but are considered different by `Eq` and `Hash`.

The `Ident` issue is now fixed.
@spastorino spastorino force-pushed the trait-inheritance-self2 branch 3 times, most recently from 6f3b0b4 to c01c135 Compare February 8, 2021 16:02
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@bors r=nikomatsakis

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bors commented Feb 8, 2021

📌 Commit 8d17c6a has been approved by nikomatsakis

@bors 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 Feb 8, 2021
bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 9, 2021
Rollup of 11 pull requests

Successful merges:

 - rust-lang#72209 (Add checking for no_mangle to unsafe_code lint)
 - rust-lang#80732 (Allow Trait inheritance with cycles on associated types take 2)
 - rust-lang#81697 (Add "every" as a doc alias for "all".)
 - rust-lang#81826 (Prefer match over combinators to make some Box methods inlineable)
 - rust-lang#81834 (Resolve typedef in HashMap lldb pretty-printer only if possible)
 - rust-lang#81841 ([rustbuild] Output rustdoc-json-types docs )
 - rust-lang#81849 (Expand the docs for ops::ControlFlow a bit)
 - rust-lang#81876 (parser: Fix panic in 'const impl' recovery)
 - rust-lang#81882 (:arrow_up: rust-analyzer)
 - rust-lang#81888 (Fix pretty printer macro_rules with semicolon.)
 - rust-lang#81896 (Remove outdated comment in windows' mutex.rs)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 44e526b into rust-lang:master Feb 9, 2021
@rustbot rustbot added this to the 1.52.0 milestone Feb 9, 2021
@pthariensflame
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Does this need relnotes?

@nikomatsakis
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I don't think it really needs relnotes, it's basically a minor bugfix that probably doesn't rise to that level.

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