Chalkify - Tweak Clause definition and HRTBs#49497
Chalkify - Tweak Clause definition and HRTBs#49497alexcrichton merged 2 commits intorust-lang:masterfrom
Clause definition and HRTBs#49497Conversation
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| goal: impl_trait, | ||
| hypotheses: vec![from_env], | ||
| }; | ||
| Lrc::new(vec![Clause::ForAll(ty::Binder::dummy(clause))]) |
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This could still be a Clause::Implies, no?
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In chalk, clauses which come from the program are always fully quantified so as to account for generic parameters, e.g.:
impl<T> Foo for T {}would lower to the following clause:
forall<T> { T: Foo }
In rustc, there is no concept of « quantified by type », only by lifetime (and quantification by lifetime is only used for higher ranked types like in for<‘a> fn(&’a i32)).
So the binder in front of the clause is indeed not useful for the moment, but you can view it as just a placeholder until rustc binders are reworked in order to account for types.
| goal: trait_pred, | ||
| hypotheses: where_clauses.into_iter().map(|wc| wc.into()).collect() | ||
| }; | ||
| Lrc::new(vec![Clause::ForAll(ty::Binder::dummy(clause))]) |
src/librustc_traits/lowering.rs
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| Clause::Implies(program_clause) => program_clause, | ||
| Clause::ForAll(program_clause) => program_clause.skip_binder(), | ||
| }; | ||
| // Skip the top-level binder for a less verbose output |
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very nit, but it seems like this comment is describing the let program_clause = match ... more so than the code below it
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Yeah definitely, I’ll fix that :)
| /// is equivalent to the implication `G1..Gn => D`; we usually write | ||
| /// it with the reverse implication operator `:-` to emphasize the way | ||
| /// that programs are actually solved (via backchaining, which starts | ||
| /// with the goal to solve and proceeds from there). |
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(Actually @nikomatsakis’s comment from his chalkify-engine branch :p)
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@nikomatsakis done ✅ |
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@bors r+ |
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📌 Commit 1074a22 has been approved by |
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Chalkify - Tweak `Clause` definition and HRTBs r? @nikomatsakis
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r? @nikomatsakis