MVP for chalkification #48985

scalexm · 2018-03-13T16:42:17Z

bors · 2018-03-13T18:29:02Z

☔ The latest upstream changes (presumably #48411) made this pull request unmergeable. Please resolve the merge conflicts.

nikomatsakis

This looks awesome! I left some suggestions, mostly nits of various kinds. I'm inclined to move forward quickly and do most of our iteration in tree rather than spending too much time in this PR, so we should feel free to mark some items as "follow-up work" (e.g., giving names and comments and things).

nikomatsakis · 2018-03-13T18:05:17Z

src/librustc/ich/impls_ty.rs

@@ -1237,3 +1237,86 @@ for ty::UniverseIndex {
        self.depth().hash_stable(hcx, hasher);
    }
 }
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for traits::WhereClauseAtom<'tcx> {


egads we should really extend the macro here

nikomatsakis · 2018-03-13T18:11:49Z

src/librustc/traits/mod.rs

@@ -242,6 +244,59 @@ pub type Obligations<'tcx, O> = Vec<Obligation<'tcx, O>>;
 pub type PredicateObligations<'tcx> = Vec<PredicateObligation<'tcx>>;
 pub type TraitObligations<'tcx> = Vec<TraitObligation<'tcx>>;

+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub enum WhereClauseAtom<'tcx> {
+    Implemented(ty::PolyTraitPredicate<'tcx>),


I don't think we want poly trait predicates here. I think we want the binders to be moved out of WhereClauseAtom and into the Goal -- actually, in Chalk we get this mildly wrong, as I'll comment below.

nikomatsakis · 2018-03-13T18:12:52Z

src/librustc/traits/mod.rs

+    Implies(Vec<DomainGoal<'tcx>>, Box<Goal<'tcx>>),
+    And(Box<Goal<'tcx>>, Box<Goal<'tcx>>),
+    Not(Box<Goal<'tcx>>),
+    Leaf(LeafGoal<'tcx>),


I think we should just call this DomainGoal, and forego the Leaf indirection

nikomatsakis · 2018-03-13T18:13:37Z

src/librustc/traits/mod.rs

+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum Goal<'tcx> {
+    Implies(Vec<DomainGoal<'tcx>>, Box<Goal<'tcx>>),


So, this matches chalk, where we make the hypotheses a set of domain goals, but it's not as general as we could do. We really should use Clause<'tcx> here, which would match the following enum:

enum Clause<'tcx> { Implies(Vec<Goal<'tcx>>, DomainGoal<'tcx>), DomainGoal(DomainGoal<'tcx>), ForAll(Box<ty::Binder<Clause<'tcx>>), }

This matches the definition from Page 7 of "A Proof Procedure for the Logic of Hereditary Harrop Formulas" pretty well. That definition is D = A | G => A | D ^ D | forall x. D -- where D is a clause, G is a goal, and A is a DomainGoal -- but we've moved the "and" case (D ^ D) into the vector. (There are broader definitions as well for clauses, but they can be normalized into this form.)

This would also entail a change to Environment to store these clauses instead of just domain goals.

The reason that this matters is that if we move the binder out of DomainGoal, we need somewhere to put it in the case of a clause!

Also, I think we should use interners probably, and hence make this:

type Goal<'tcx> = &'tcx GoalKind<'tcx>; enum GoalKind<'tcx> { Implies(Vec<DomainGoal<'tcx>, Goal<'tcx>), ... // as today }

but we can do that in a follow-up. (We should open a FIXME for it before landing.)

I opened rust-lang/chalk#94 to describe the change here in chalk

nikomatsakis · 2018-03-13T18:21:55Z

src/librustc/traits/structural_impls.rs

+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "{}", self.consequence)?;
+        if self.conditions.is_empty() {
+            write!(fmt, ".")?;


Total nit: let's either keep the . on both sides or drop it on both sides. =)

nikomatsakis · 2018-03-13T18:23:46Z

src/librustc/traits/structural_impls.rs

+    }
+}
+
+impl<'tcx> TypeFoldable<'tcx> for traits::WhereClauseAtom<'tcx> {


There are pretty decent macros for this... oh, shoot, they are in #48411 -- oh, wait, that just landed =)

You may want to adopt one of these:

rust/src/librustc/macros.rs

Lines 160 to 164 in 8c4ff22

///////////////////////////////////////////////////////////////////////////

// Lift and TypeFoldable macros

//

// When possible, use one of these (relatively) convenient macros to write

// the impls for you.

nikomatsakis · 2018-03-13T18:25:00Z

src/test/ui/chalkify/lower_impl.rs

+
+trait Foo { }
+
+#[rustc_dump_program_clauses] //~ ERROR Implemented(T: Foo) :-


This is so nice =) I guess you intentionally omitted the details here? (We see them below in the stderr file...)

Yes I skipped them here because it's a bit verbose :)

nikomatsakis · 2018-03-13T18:27:36Z

src/librustc/traits/lowering.rs

+    fn lower(&self) -> DomainGoal<'tcx> {
+        use self::Predicate::*;
+
+        match *self {


Nit; you don't need the *self anymore; you can add the feature(match_default_bindings) instead

nikomatsakis · 2018-03-13T18:30:30Z

src/librustc/traits/lowering.rs

+    let trait_ref = ty::Binder(TraitPredicate { trait_ref }).lower();
+    let where_clauses = tcx.predicates_of(def_id).predicates.lower();
+
+    let clause = ProgramClause {


Hmm. So, I think we should go through the rustc-guide reference on this topic and give names to each of these rules. Then we can reference those rules here to allow for easy cross-reference.

This can be done later.

nikomatsakis · 2018-03-13T18:31:34Z

src/librustc/traits/lowering.rs

+use ty::{self, PolyTraitPredicate, TraitPredicate, PolyProjectionPredicate, TyCtxt, Predicate};
+use super::{DomainGoal, ProgramClause, WhereClauseAtom};
+use rustc_data_structures::sync::Lrc;
+use syntax::ast;


Nit: let's move this code into librustc_traits now that #48411 has landed

nikomatsakis · 2018-03-13T21:24:53Z

ok so I was talking to @scalexm on gitter. We agreed that we can leave most of the changes here for later. Here is the list of thing I wrote, I think:

Move binder out of domain goal and into clause (comment, comment 2)
Use interned refs instead of boxes -- Deferred to 🛠 use interned refs to goals/clauses instead of boxes #49054
Drop the dot
Adopt macros for type folder and friends
Consider default-match-bindings
[Give names to the rules in rustc-guide and use them in code] -- Deferable
Move code into librustc_traits
Fix the printing of higher-ranked things (existing FIXME) -- Deferable

nikomatsakis · 2018-03-13T21:25:23Z

@scalexm I'd like to review one last time tomorrow or whatever, but otherwise once nits are fixed I think we should land and then we can open up issues for follow-up work

nikomatsakis · 2018-03-15T18:28:36Z

@bors r+

This is so exciting. 🎉

bors · 2018-03-15T18:28:41Z

📌 Commit 4eaa85d has been approved by nikomatsakis

kennytm · 2018-03-15T22:17:54Z

src/librustc_traits/lowering.rs

+    if let ImplPolarity::Negative = tcx.impl_polarity(def_id) {
+        return Lrc::new(vec![]);
+    }
+


[00:06:08] tidy error: /checkout/src/librustc_traits/lowering.rs:120: trailing whitespace [00:06:10] some tidy checks failed

kennytm · 2018-03-15T22:18:23Z

@bors r-

Tidy failed.

kennytm · 2018-03-15T22:22:15Z

@bors r=nikomatsakis

bors · 2018-03-15T22:22:16Z

📌 Commit ef3b4e1 has been approved by nikomatsakis

bors · 2018-03-18T07:35:51Z

⌛ Testing commit ef3b4e1 with merge 7c396eb...

@nikomatsakis

MVP for chalkification r? @nikomatsakis

bors · 2018-03-18T10:03:13Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 7c396eb to master...

rust-highfive assigned nikomatsakis Mar 13, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 13, 2018

nikomatsakis requested changes Mar 13, 2018

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scalexm added 2 commits March 14, 2018 13:39

Add MVP for chalkification

1271f0b

Address niko's nits

04b228c

scalexm force-pushed the lowering branch from d1019a5 to 04b228c Compare March 14, 2018 13:14

scalexm added 2 commits March 14, 2018 14:45

Move code into librustc_traits

2bbd16d

Add documentation

e8f3ed5

scalexm changed the title ~~[WIP] MVP for chalkification~~ MVP for chalkification Mar 14, 2018

nikomatsakis mentioned this pull request Mar 15, 2018

🛠 use interned refs to goals/clauses instead of boxes #49054

Closed

add xref to rust-guide

4eaa85d

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 Mar 15, 2018

kennytm reviewed Mar 15, 2018

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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 Mar 15, 2018

Fix tidy

ef3b4e1

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 Mar 15, 2018

bors added a commit that referenced this pull request Mar 18, 2018

Auto merge of #48985 - scalexm:lowering, r=nikomatsakis

7c396eb

MVP for chalkification r? @nikomatsakis

bors mentioned this pull request Mar 18, 2018

[WIP] Deduplicate instances #48139

Closed

4 tasks

bors merged commit ef3b4e1 into rust-lang:master Mar 18, 2018

bors mentioned this pull request Mar 18, 2018

Create a canonical trait query for evaluate_obligation #48995

Merged

nikomatsakis mentioned this pull request Mar 19, 2018

🛠 Extend the "chalk lowering" pass with remaining rules #49177

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scalexm deleted the lowering branch October 22, 2018 12:19

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MVP for chalkification #48985

MVP for chalkification #48985

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	///////////////////////////////////////////////////////////////////////////
	// Lift and TypeFoldable macros
	//
	// When possible, use one of these (relatively) convenient macros to write
	// the impls for you.


		trait Foo { }

		#[rustc_dump_program_clauses] //~ ERROR Implemented(T: Foo) :-

MVP for chalkification #48985

MVP for chalkification #48985

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