/
relate_tys.rs
111 lines (100 loc) · 3.92 KB
/
relate_tys.rs
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// Copyright 2017 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.
use borrow_check::nll::constraints::OutlivesConstraint;
use borrow_check::nll::type_check::{BorrowCheckContext, Locations};
use rustc::infer::nll_relate::{TypeRelating, TypeRelatingDelegate};
use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
use rustc::mir::ConstraintCategory;
use rustc::traits::query::Fallible;
use rustc::ty::relate::TypeRelation;
use rustc::ty::{self, Ty};
/// Adds sufficient constraints to ensure that `a R b` where `R` depends on `v`:
///
/// - "Covariant" `a <: b`
/// - "Invariant" `a == b`
/// - "Contravariant" `a :> b`
///
/// NB. The type `a` is permitted to have unresolved inference
/// variables, but not the type `b`.
pub(super) fn relate_types<'tcx>(
infcx: &InferCtxt<'_, '_, 'tcx>,
a: Ty<'tcx>,
v: ty::Variance,
b: Ty<'tcx>,
locations: Locations,
category: ConstraintCategory,
borrowck_context: Option<&mut BorrowCheckContext<'_, 'tcx>>,
) -> Fallible<()> {
debug!("eq_types(a={:?}, b={:?}, locations={:?})", a, b, locations);
TypeRelating::new(
infcx,
NllTypeRelatingDelegate::new(infcx, borrowck_context, locations, category),
v,
).relate(&a, &b)?;
Ok(())
}
struct NllTypeRelatingDelegate<'me, 'bccx: 'me, 'gcx: 'tcx, 'tcx: 'bccx> {
infcx: &'me InferCtxt<'me, 'gcx, 'tcx>,
borrowck_context: Option<&'me mut BorrowCheckContext<'bccx, 'tcx>>,
/// Where (and why) is this relation taking place?
locations: Locations,
/// What category do we assign the resulting `'a: 'b` relationships?
category: ConstraintCategory,
}
impl NllTypeRelatingDelegate<'me, 'bccx, 'gcx, 'tcx> {
fn new(
infcx: &'me InferCtxt<'me, 'gcx, 'tcx>,
borrowck_context: Option<&'me mut BorrowCheckContext<'bccx, 'tcx>>,
locations: Locations,
category: ConstraintCategory,
) -> Self {
Self {
infcx,
borrowck_context,
locations,
category,
}
}
}
impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, '_, 'tcx> {
fn create_next_universe(&mut self) -> ty::UniverseIndex {
self.infcx.create_next_universe()
}
fn next_existential_region_var(&mut self) -> ty::Region<'tcx> {
let origin = NLLRegionVariableOrigin::Existential;
self.infcx.next_nll_region_var(origin)
}
fn next_placeholder_region(&mut self, placeholder: ty::Placeholder) -> ty::Region<'tcx> {
let origin = NLLRegionVariableOrigin::Placeholder(placeholder);
if let Some(borrowck_context) = &mut self.borrowck_context {
borrowck_context.constraints.placeholder_indices.insert(placeholder);
}
self.infcx.next_nll_region_var(origin)
}
fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> {
self.infcx
.next_nll_region_var_in_universe(NLLRegionVariableOrigin::Existential, universe)
}
fn push_outlives(&mut self, sup: ty::Region<'tcx>, sub: ty::Region<'tcx>) {
if let Some(borrowck_context) = &mut self.borrowck_context {
let sub = borrowck_context.universal_regions.to_region_vid(sub);
let sup = borrowck_context.universal_regions.to_region_vid(sup);
borrowck_context
.constraints
.outlives_constraints
.push(OutlivesConstraint {
sup,
sub,
locations: self.locations,
category: self.category,
});
}
}
}