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Auto merge of #49435 - tmandry:rule-implied-bound-from-trait, r=nikomatsakis

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chalkify: Implement lowering rule Implied-Bound-From-Trait

For #49177.

TODO:
- [x] Implement where clauses besides trait and projection predicates
- [x] Is the output of the `lower_trait_higher_rank` test correct?
- [ ] Remove `Self::Trait` from the query `tcx.predicates_of(<trait_id>).predicates`
- [ ] Consider moving tests to compile-fail to make them more manageable
This commit is contained in:
bors 2018-04-10 00:32:54 +00:00
commit a8a8d6b5bf
7 changed files with 212 additions and 5 deletions
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69
src/librustc_traits/lowering.rs
View File

@ -90,6 +90,28 @@ impl<'tcx> Lower<PolyDomainGoal<'tcx>> for ty::Predicate<'tcx> {
}
}
/// Transforms an existing goal into a FromEnv goal.
///
/// Used for lowered where clauses (see rustc guide).
trait IntoFromEnvGoal {
fn into_from_env_goal(self) -> Self;
}
impl<'tcx> IntoFromEnvGoal for DomainGoal<'tcx> {
fn into_from_env_goal(self) -> DomainGoal<'tcx> {
use self::DomainGoal::*;
match self {
Holds(wc_atom) => FromEnv(wc_atom),
WellFormed(..) |
FromEnv(..) |
WellFormedTy(..) |
FromEnvTy(..) |
RegionOutlives(..) |
TypeOutlives(..) => self,
}
}
}
crate fn program_clauses_for<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-> Lrc<Vec<Clause<'tcx>>>
{
@ -107,9 +129,9 @@ crate fn program_clauses_for<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefI
fn program_clauses_for_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-> Lrc<Vec<Clause<'tcx>>>
{
// Rule Implemented-From-Env (see rustc guide)
//
// `trait Trait<P1..Pn> where WC { .. } // P0 == Self`
// Rule Implemented-From-Env (see rustc guide)
//
// ```
// forall<Self, P1..Pn> {
@ -130,11 +152,50 @@ fn program_clauses_for_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefI
let impl_trait = DomainGoal::Holds(WhereClauseAtom::Implemented(trait_pred));
// `Implemented(Self: Trait<P1..Pn>) :- FromEnv(Self: Trait<P1..Pn>)`
let clause = ProgramClause {
let implemented_from_env = ProgramClause {
goal: impl_trait,
hypotheses: vec![from_env],
};
Lrc::new(vec![Clause::ForAll(ty::Binder::dummy(clause))])
let mut clauses = vec![
Clause::ForAll(ty::Binder::dummy(implemented_from_env))
];
// Rule Implied-Bound-From-Trait
//
// For each where clause WC:
// ```
// forall<Self, P1..Pn> {
// FromEnv(WC) :- FromEnv(Self: Trait<P1..Pn)
// }
// ```
// `FromEnv(WC) :- FromEnv(Self: Trait<P1..Pn>)`, for each where clause WC
// FIXME: Remove the [1..] slice; this is a hack because the query
// predicates_of currently includes the trait itself (`Self: Trait<P1..Pn>`).
let where_clauses = &tcx.predicates_of(def_id).predicates;
let implied_bound_clauses =
where_clauses[1..].into_iter()
.map(|wc| implied_bound_from_trait(trait_pred, wc));
clauses.extend(implied_bound_clauses);
Lrc::new(clauses)
}
/// For a given `where_clause`, returns a clause `FromEnv(WC) :- FromEnv(Self: Trait<P1..Pn>)`.
fn implied_bound_from_trait<'tcx>(
trait_pred: ty::TraitPredicate<'tcx>,
where_clause: &ty::Predicate<'tcx>,
) -> Clause<'tcx> {
// `FromEnv(Self: Trait<P1..Pn>)`
let impl_trait = DomainGoal::FromEnv(WhereClauseAtom::Implemented(trait_pred));
// `FromEnv(WC) :- FromEnv(Self: Trait<P1..Pn>)`
Clause::ForAll(
where_clause.lower().map_bound(|goal| ProgramClause {
goal: goal.into_from_env_goal(),
hypotheses: vec![impl_trait.into()],
})
)
}
fn program_clauses_for_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)

3
src/test/ui/chalkify/lower_trait.rs
View File

@ -11,6 +11,9 @@
#![feature(rustc_attrs)]
#[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<S, T, U>) :-
//~| ERROR FromEnv
//~| ERROR FromEnv
//~| ERROR FromEnv
trait Foo<S, T, U> {
fn s(S) -> S;
fn t(T) -> T;

20
src/test/ui/chalkify/lower_trait.stderr
View File

@ -4,5 +4,23 @@ error: Implemented(Self: Foo<S, T, U>) :- FromEnv(Self: Foo<S, T, U>).
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
error: FromEnv(S: std::marker::Sized) :- FromEnv(Self: Foo<S, T, U>).
--> $DIR/lower_trait.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(T: std::marker::Sized) :- FromEnv(Self: Foo<S, T, U>).
--> $DIR/lower_trait.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(U: std::marker::Sized) :- FromEnv(Self: Foo<S, T, U>).
--> $DIR/lower_trait.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 4 previous errors

24
src/test/ui/chalkify/lower_trait_higher_rank.rs Normal file
View File

@ -0,0 +1,24 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(rustc_attrs)]
#[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<F>) :-
//~| ERROR FromEnv
//~| ERROR FromEnv
//~| ERROR FromEnv
trait Foo<F> where for<'a> F: Fn(&'a (u8, u16)) -> &'a u8
{
fn s(F) -> F;
}
fn main() {
println!("hello");
}

26
src/test/ui/chalkify/lower_trait_higher_rank.stderr Normal file
View File

@ -0,0 +1,26 @@
error: Implemented(Self: Foo<F>) :- FromEnv(Self: Foo<F>).
--> $DIR/lower_trait_higher_rank.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<F>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(F: std::marker::Sized) :- FromEnv(Self: Foo<F>).
--> $DIR/lower_trait_higher_rank.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<F>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(F: std::ops::Fn<(&'a (u8, u16),)>) :- FromEnv(Self: Foo<F>).
--> $DIR/lower_trait_higher_rank.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<F>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(<F as std::ops::FnOnce<(&'a (u8, u16),)>>::Output == &'a u8) :- FromEnv(Self: Foo<F>).
--> $DIR/lower_trait_higher_rank.rs:13:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<F>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 4 previous errors

31
src/test/ui/chalkify/lower_trait_where_clause.rs Normal file
View File

@ -0,0 +1,31 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(rustc_attrs)]
use std::fmt::{Debug, Display};
use std::borrow::Borrow;
#[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
//~| ERROR FromEnv
//~| ERROR FromEnv
//~| ERROR FromEnv
//~| ERROR FromEnv
//~| ERROR RegionOutlives
//~| ERROR TypeOutlives
trait Foo<'a, 'b, S, T, U> where S: Debug, T: Borrow<U>, U: ?Sized, 'a: 'b, U: 'b {
fn s(S) -> S;
fn t(T) -> T;
fn u(U) -> U;
}
fn main() {
println!("hello");
}

44
src/test/ui/chalkify/lower_trait_where_clause.stderr Normal file
View File

@ -0,0 +1,44 @@
error: Implemented(Self: Foo<'a, 'b, S, T, U>) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(S: std::marker::Sized) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(T: std::marker::Sized) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(S: std::fmt::Debug) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: FromEnv(T: std::borrow::Borrow<U>) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: RegionOutlives('a : 'b) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: TypeOutlives(U : 'b) :- FromEnv(Self: Foo<'a, 'b, S, T, U>).
--> $DIR/lower_trait_where_clause.rs:16:1
|
LL | #[rustc_dump_program_clauses] //~ ERROR Implemented(Self: Foo<'a, 'b, S, T, U>) :-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 7 previous errors