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|
use rustc_infer::infer::nll_relate::{TypeRelating, TypeRelatingDelegate};
use rustc_infer::infer::NllRegionVariableOrigin;
use rustc_infer::traits::PredicateObligations;
use rustc_middle::mir::ConstraintCategory;
use rustc_middle::ty::relate::TypeRelation;
use rustc_middle::ty::{self, Ty};
use rustc_span::{Span, Symbol};
use rustc_trait_selection::traits::query::Fallible;
use crate::constraints::OutlivesConstraint;
use crate::diagnostics::UniverseInfo;
use crate::renumber::{BoundRegionInfo, RegionCtxt};
use crate::type_check::{InstantiateOpaqueType, Locations, TypeChecker};
impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
/// Adds sufficient constraints to ensure that `a R b` where `R` depends on `v`:
///
/// - "Covariant" `a <: b`
/// - "Invariant" `a == b`
/// - "Contravariant" `a :> b`
///
/// N.B., the type `a` is permitted to have unresolved inference
/// variables, but not the type `b`.
#[instrument(skip(self), level = "debug")]
pub(super) fn relate_types(
&mut self,
a: Ty<'tcx>,
v: ty::Variance,
b: Ty<'tcx>,
locations: Locations,
category: ConstraintCategory<'tcx>,
) -> Fallible<()> {
TypeRelating::new(
self.infcx,
NllTypeRelatingDelegate::new(self, locations, category, UniverseInfo::relate(a, b)),
v,
)
.relate(a, b)?;
Ok(())
}
/// Add sufficient constraints to ensure `a == b`. See also [Self::relate_types].
pub(super) fn eq_substs(
&mut self,
a: ty::SubstsRef<'tcx>,
b: ty::SubstsRef<'tcx>,
locations: Locations,
category: ConstraintCategory<'tcx>,
) -> Fallible<()> {
TypeRelating::new(
self.infcx,
NllTypeRelatingDelegate::new(self, locations, category, UniverseInfo::other()),
ty::Variance::Invariant,
)
.relate(a, b)?;
Ok(())
}
}
struct NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
type_checker: &'me mut TypeChecker<'bccx, 'tcx>,
/// Where (and why) is this relation taking place?
locations: Locations,
/// What category do we assign the resulting `'a: 'b` relationships?
category: ConstraintCategory<'tcx>,
/// Information so that error reporting knows what types we are relating
/// when reporting a bound region error.
universe_info: UniverseInfo<'tcx>,
}
impl<'me, 'bccx, 'tcx> NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
fn new(
type_checker: &'me mut TypeChecker<'bccx, 'tcx>,
locations: Locations,
category: ConstraintCategory<'tcx>,
universe_info: UniverseInfo<'tcx>,
) -> Self {
Self { type_checker, locations, category, universe_info }
}
}
impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
fn span(&self) -> Span {
self.locations.span(self.type_checker.body)
}
fn param_env(&self) -> ty::ParamEnv<'tcx> {
self.type_checker.param_env
}
fn create_next_universe(&mut self) -> ty::UniverseIndex {
let universe = self.type_checker.infcx.create_next_universe();
self.type_checker
.borrowck_context
.constraints
.universe_causes
.insert(universe, self.universe_info.clone());
universe
}
#[instrument(skip(self), level = "debug")]
fn next_existential_region_var(
&mut self,
from_forall: bool,
_name: Option<Symbol>,
) -> ty::Region<'tcx> {
let origin = NllRegionVariableOrigin::Existential { from_forall };
let reg_var =
self.type_checker.infcx.next_nll_region_var(origin, || RegionCtxt::Existential(_name));
reg_var
}
#[instrument(skip(self), level = "debug")]
fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> {
let reg = self
.type_checker
.borrowck_context
.constraints
.placeholder_region(self.type_checker.infcx, placeholder);
let reg_info = match placeholder.name {
ty::BoundRegionKind::BrAnon(_, Some(span)) => BoundRegionInfo::Span(span),
ty::BoundRegionKind::BrAnon(..) => BoundRegionInfo::Name(Symbol::intern("anon")),
ty::BoundRegionKind::BrNamed(_, name) => BoundRegionInfo::Name(name),
ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(Symbol::intern("env")),
};
let reg_var =
reg.as_var().unwrap_or_else(|| bug!("expected region {:?} to be of kind ReVar", reg));
let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
let prev = var_to_origin.insert(reg_var, RegionCtxt::Placeholder(reg_info));
assert!(matches!(prev, None));
reg
}
#[instrument(skip(self), level = "debug")]
fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> {
let reg = self.type_checker.infcx.next_nll_region_var_in_universe(
NllRegionVariableOrigin::Existential { from_forall: false },
universe,
);
let reg_var =
reg.as_var().unwrap_or_else(|| bug!("expected region {:?} to be of kind ReVar", reg));
if cfg!(debug_assertions) {
let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
let prev = var_to_origin.insert(reg_var, RegionCtxt::Existential(None));
// It only makes sense to track region vars in non-canonicalization contexts. If this
// ever changes we either want to get rid of `BorrowckInferContext::reg_var_to_origin`
// or modify how we track nll region vars for that map.
assert!(matches!(prev, None));
}
reg
}
fn push_outlives(
&mut self,
sup: ty::Region<'tcx>,
sub: ty::Region<'tcx>,
info: ty::VarianceDiagInfo<'tcx>,
) {
let sub = self.type_checker.borrowck_context.universal_regions.to_region_vid(sub);
let sup = self.type_checker.borrowck_context.universal_regions.to_region_vid(sup);
self.type_checker.borrowck_context.constraints.outlives_constraints.push(
OutlivesConstraint {
sup,
sub,
locations: self.locations,
span: self.locations.span(self.type_checker.body),
category: self.category,
variance_info: info,
from_closure: false,
},
);
}
fn forbid_inference_vars() -> bool {
true
}
fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
self.type_checker
.fully_perform_op(
self.locations,
self.category,
InstantiateOpaqueType {
obligations,
// These fields are filled in during execution of the operation
base_universe: None,
region_constraints: None,
},
)
.unwrap();
}
}
|
