[MCP] introduce ty::WhereClause to align chalk and rustc dyn repr

[csmoe]

Closes rust-lang/types-team#30
Closes rust-lang/compiler-team#433
r? @nikomatsakis

[rust-highfive]

Some changes occured to the CTFE / Miri engine

cc @rust-lang/miri

[bors]

☔ The latest upstream changes (presumably #85954) made this pull request unmergeable. Please resolve the merge conflicts.

[csmoe]

@nikomatsakis ping for a review🔔

[jackh726]

This isn't quite right. The difference between rustc and Chalk isn't solely the name. In Chalk, there's actually two layers of Binders. One that contains a single type that represents Self, and one that represents the vars on the predicates itself. See https://github.com/rust-lang/chalk/blob/802599ce2ca02f322c078f472e64c5cd3a208225/chalk-solve/src/rust_ir.rs#L233

edit: this isn't actually accurate; let me write up a better comment

[jackh726]

I guess the big thing missing here is the removal of erase_self_ty. And along with that, make the Self ty actually be a bound var.

[bors]

☔ The latest upstream changes (presumably #87424) made this pull request unmergeable. Please resolve the merge conflicts.

[JohnCSimon]

ping from triage:
@csmoe
Returning to you to address merge conflicts and after that switch this back to S-waiting-on-review.
thanks.

[nikomatsakis]

@csmoe sorry this PR disappeared from my radar

[nikomatsakis]

Are you still around?

[csmoe]

Are you still around?

yep, time was tough. I'm back on this:)

[nikomatsakis]

Augh! Let me give this a quick review @csmoe

[nikomatsakis]

OK, so, I read the PR. From what I can tell, before this PR:

• We have Binder<ExistentialPredicate>, where ExistentialPredicate is a subset of predicates that don't have Self position specified.

After this PR:

• We introduce WhereClause to be the old ExistentialPredicate, and we make ExistentialPredicate an alias for Binder<WC>

This seems good, but indeed only a first step in the ultimate direction. Ultimately we want to extend WhereClause so it includes the Self type, and @jackh726 is right that this will mean introducing another level of Binder.

I think we also want to share WhereClause with Predicate.

[bors]

☔ The latest upstream changes (presumably #89619) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #90734) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-log-analyzer]

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.58.0-nightly (6f7dc9a98 2021-11-14) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z symbol-mangling-version=legacy -Z macro-backtrace -Z crate-attr=doc(html_root_url="https://doc.rust-lang.org/nightly/") -Z binary-dep-depinfo -Z force-unstable-if-unmarked -C opt-level=3 -C embed-bitcode=no -C codegen-units=1 -C debuginfo=0 -C debug-assertions=on -C link-args=-Wl,-rpath,$ORIGIN/../lib -C prefer-dynamic -C llvm-args=-import-instr-limit=10 -C embed-bitcode=yes --crate-type lib
note: some of the compiler flags provided by cargo are hidden

query stack during panic:
query stack during panic:
#0 [inferred_outlives_crate] computing the inferred outlives predicates for items in this crate
#1 [inferred_outlives_of] computing inferred outlives predicates of `cell::UnsafeCell`
error: could not compile `core`
Build completed unsuccessfully in 0:04:06

[bors]

☔ The latest upstream changes (presumably #91230) made this pull request unmergeable. Please resolve the merge conflicts.

[crlf0710]

@csmoe Ping from triage: Any updates here?

[Dylan-DPC]

Closing this as inactive