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use std::cell::{Cell, RefCell};
use std::fmt;
pub use at::DefineOpaqueTypes;
use free_regions::RegionRelations;
pub use freshen::TypeFreshener;
use lexical_region_resolve::LexicalRegionResolutions;
pub use lexical_region_resolve::RegionResolutionError;
use opaque_types::OpaqueTypeStorage;
use region_constraints::{
GenericKind, RegionConstraintCollector, RegionConstraintStorage, VarInfos, VerifyBound,
};
pub use relate::combine::{CombineFields, PredicateEmittingRelation};
pub use relate::StructurallyRelateAliases;
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
use rustc_data_structures::sync::Lrc;
use rustc_data_structures::undo_log::Rollback;
use rustc_data_structures::unify as ut;
use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_macros::extension;
pub use rustc_macros::{TypeFoldable, TypeVisitable};
use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
use rustc_middle::infer::unify_key::{
ConstVariableOrigin, ConstVariableValue, ConstVidKey, EffectVarValue, EffectVidKey,
};
use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
use rustc_middle::mir::ConstraintCategory;
use rustc_middle::traits::select;
use rustc_middle::traits::solve::{Goal, NoSolution};
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::{
BoundVarReplacerDelegate, TypeFoldable, TypeFolder, TypeSuperFoldable,
};
use rustc_middle::ty::visit::TypeVisitableExt;
pub use rustc_middle::ty::IntVarValue;
use rustc_middle::ty::{
self, ConstVid, EffectVid, FloatVid, GenericArg, GenericArgKind, GenericArgs, GenericArgsRef,
GenericParamDefKind, InferConst, IntVid, Ty, TyCtxt, TyVid,
};
use rustc_middle::{bug, span_bug};
use rustc_span::symbol::Symbol;
use rustc_span::Span;
use snapshot::undo_log::InferCtxtUndoLogs;
use tracing::{debug, instrument};
use type_variable::TypeVariableOrigin;
pub use BoundRegionConversionTime::*;
pub use RegionVariableOrigin::*;
pub use SubregionOrigin::*;
use crate::infer::relate::RelateResult;
use crate::traits::{self, ObligationCause, ObligationInspector, PredicateObligation, TraitEngine};
pub mod at;
pub mod canonical;
mod context;
pub mod free_regions;
mod freshen;
mod lexical_region_resolve;
pub mod opaque_types;
pub mod outlives;
mod projection;
pub mod region_constraints;
pub mod relate;
pub mod resolve;
pub(crate) mod snapshot;
pub mod type_variable;
#[must_use]
#[derive(Debug)]
pub struct InferOk<'tcx, T> {
pub value: T,
pub obligations: Vec<PredicateObligation<'tcx>>,
}
pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable<
ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'tcx>>,
>;
/// This type contains all the things within `InferCtxt` that sit within a
/// `RefCell` and are involved with taking/rolling back snapshots. Snapshot
/// operations are hot enough that we want only one call to `borrow_mut` per
/// call to `start_snapshot` and `rollback_to`.
#[derive(Clone)]
pub struct InferCtxtInner<'tcx> {
undo_log: InferCtxtUndoLogs<'tcx>,
/// Cache for projections.
///
/// This cache is snapshotted along with the infcx.
projection_cache: traits::ProjectionCacheStorage<'tcx>,
/// We instantiate `UnificationTable` with `bounds<Ty>` because the types
/// that might instantiate a general type variable have an order,
/// represented by its upper and lower bounds.
type_variable_storage: type_variable::TypeVariableStorage<'tcx>,
/// Map from const parameter variable to the kind of const it represents.
const_unification_storage: ut::UnificationTableStorage<ConstVidKey<'tcx>>,
/// Map from integral variable to the kind of integer it represents.
int_unification_storage: ut::UnificationTableStorage<ty::IntVid>,
/// Map from floating variable to the kind of float it represents.
float_unification_storage: ut::UnificationTableStorage<ty::FloatVid>,
/// Map from effect variable to the effect param it represents.
effect_unification_storage: ut::UnificationTableStorage<EffectVidKey<'tcx>>,
/// Tracks the set of region variables and the constraints between them.
///
/// This is initially `Some(_)` but when
/// `resolve_regions_and_report_errors` is invoked, this gets set to `None`
/// -- further attempts to perform unification, etc., may fail if new
/// region constraints would've been added.
region_constraint_storage: Option<RegionConstraintStorage<'tcx>>,
/// A set of constraints that regionck must validate.
///
/// Each constraint has the form `T:'a`, meaning "some type `T` must
/// outlive the lifetime 'a". These constraints derive from
/// instantiated type parameters. So if you had a struct defined
/// like the following:
/// ```ignore (illustrative)
/// struct Foo<T: 'static> { ... }
/// ```
/// In some expression `let x = Foo { ... }`, it will
/// instantiate the type parameter `T` with a fresh type `$0`. At
/// the same time, it will record a region obligation of
/// `$0: 'static`. This will get checked later by regionck. (We
/// can't generally check these things right away because we have
/// to wait until types are resolved.)
///
/// These are stored in a map keyed to the id of the innermost
/// enclosing fn body / static initializer expression. This is
/// because the location where the obligation was incurred can be
/// relevant with respect to which sublifetime assumptions are in
/// place. The reason that we store under the fn-id, and not
/// something more fine-grained, is so that it is easier for
/// regionck to be sure that it has found *all* the region
/// obligations (otherwise, it's easy to fail to walk to a
/// particular node-id).
///
/// Before running `resolve_regions_and_report_errors`, the creator
/// of the inference context is expected to invoke
/// [`InferCtxt::process_registered_region_obligations`]
/// for each body-id in this map, which will process the
/// obligations within. This is expected to be done 'late enough'
/// that all type inference variables have been bound and so forth.
region_obligations: Vec<RegionObligation<'tcx>>,
/// Caches for opaque type inference.
opaque_type_storage: OpaqueTypeStorage<'tcx>,
}
impl<'tcx> InferCtxtInner<'tcx> {
fn new() -> InferCtxtInner<'tcx> {
InferCtxtInner {
undo_log: InferCtxtUndoLogs::default(),
projection_cache: Default::default(),
type_variable_storage: type_variable::TypeVariableStorage::new(),
const_unification_storage: ut::UnificationTableStorage::new(),
int_unification_storage: ut::UnificationTableStorage::new(),
float_unification_storage: ut::UnificationTableStorage::new(),
effect_unification_storage: ut::UnificationTableStorage::new(),
region_constraint_storage: Some(RegionConstraintStorage::new()),
region_obligations: vec![],
opaque_type_storage: Default::default(),
}
}
#[inline]
pub fn region_obligations(&self) -> &[RegionObligation<'tcx>] {
&self.region_obligations
}
#[inline]
pub fn projection_cache(&mut self) -> traits::ProjectionCache<'_, 'tcx> {
self.projection_cache.with_log(&mut self.undo_log)
}
#[inline]
fn try_type_variables_probe_ref(
&self,
vid: ty::TyVid,
) -> Option<&type_variable::TypeVariableValue<'tcx>> {
// Uses a read-only view of the unification table, this way we don't
// need an undo log.
self.type_variable_storage.eq_relations_ref().try_probe_value(vid)
}
#[inline]
fn type_variables(&mut self) -> type_variable::TypeVariableTable<'_, 'tcx> {
self.type_variable_storage.with_log(&mut self.undo_log)
}
#[inline]
pub fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'tcx> {
self.opaque_type_storage.with_log(&mut self.undo_log)
}
#[inline]
fn int_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ty::IntVid> {
self.int_unification_storage.with_log(&mut self.undo_log)
}
#[inline]
fn float_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ty::FloatVid> {
self.float_unification_storage.with_log(&mut self.undo_log)
}
#[inline]
fn const_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ConstVidKey<'tcx>> {
self.const_unification_storage.with_log(&mut self.undo_log)
}
fn effect_unification_table(&mut self) -> UnificationTable<'_, 'tcx, EffectVidKey<'tcx>> {
self.effect_unification_storage.with_log(&mut self.undo_log)
}
#[inline]
pub fn unwrap_region_constraints(&mut self) -> RegionConstraintCollector<'_, 'tcx> {
self.region_constraint_storage
.as_mut()
.expect("region constraints already solved")
.with_log(&mut self.undo_log)
}
// Iterates through the opaque type definitions without taking them; this holds the
// `InferCtxtInner` lock, so make sure to not do anything with `InferCtxt` side-effects
// while looping through this.
pub fn iter_opaque_types(
&self,
) -> impl Iterator<Item = (ty::OpaqueTypeKey<'tcx>, ty::OpaqueHiddenType<'tcx>)> + '_ {
self.opaque_type_storage.opaque_types.iter().map(|(&k, v)| (k, v.hidden_type))
}
}
pub struct InferCtxt<'tcx> {
pub tcx: TyCtxt<'tcx>,
/// The `DefIds` of the opaque types that may have their hidden types constrained.
defining_opaque_types: &'tcx ty::List<LocalDefId>,
/// Whether this inference context should care about region obligations in
/// the root universe. Most notably, this is used during hir typeck as region
/// solving is left to borrowck instead.
pub considering_regions: bool,
/// If set, this flag causes us to skip the 'leak check' during
/// higher-ranked subtyping operations. This flag is a temporary one used
/// to manage the removal of the leak-check: for the time being, we still run the
/// leak-check, but we issue warnings.
skip_leak_check: bool,
pub inner: RefCell<InferCtxtInner<'tcx>>,
/// Once region inference is done, the values for each variable.
lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
/// Caches the results of trait selection. This cache is used
/// for things that have to do with the parameters in scope.
pub selection_cache: select::SelectionCache<'tcx>,
/// Caches the results of trait evaluation.
pub evaluation_cache: select::EvaluationCache<'tcx>,
/// The set of predicates on which errors have been reported, to
/// avoid reporting the same error twice.
pub reported_trait_errors:
RefCell<FxIndexMap<Span, (Vec<ty::Predicate<'tcx>>, ErrorGuaranteed)>>,
pub reported_signature_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
/// When an error occurs, we want to avoid reporting "derived"
/// errors that are due to this original failure. Normally, we
/// handle this with the `err_count_on_creation` count, which
/// basically just tracks how many errors were reported when we
/// started type-checking a fn and checks to see if any new errors
/// have been reported since then. Not great, but it works.
///
/// However, when errors originated in other passes -- notably
/// resolve -- this heuristic breaks down. Therefore, we have this
/// auxiliary flag that one can set whenever one creates a
/// type-error that is due to an error in a prior pass.
///
/// Don't read this flag directly, call `is_tainted_by_errors()`
/// and `set_tainted_by_errors()`.
tainted_by_errors: Cell<Option<ErrorGuaranteed>>,
/// Track how many errors were reported when this infcx is created.
/// If the number of errors increases, that's also a sign (like
/// `tainted_by_errors`) to avoid reporting certain kinds of errors.
// FIXME(matthewjasper) Merge into `tainted_by_errors`
err_count_on_creation: usize,
/// What is the innermost universe we have created? Starts out as
/// `UniverseIndex::root()` but grows from there as we enter
/// universal quantifiers.
///
/// N.B., at present, we exclude the universal quantifiers on the
/// item we are type-checking, and just consider those names as
/// part of the root universe. So this would only get incremented
/// when we enter into a higher-ranked (`for<..>`) type or trait
/// bound.
universe: Cell<ty::UniverseIndex>,
/// During coherence we have to assume that other crates may add
/// additional impls which we currently don't know about.
///
/// To deal with this evaluation, we should be conservative
/// and consider the possibility of impls from outside this crate.
/// This comes up primarily when resolving ambiguity. Imagine
/// there is some trait reference `$0: Bar` where `$0` is an
/// inference variable. If `intercrate` is true, then we can never
/// say for sure that this reference is not implemented, even if
/// there are *no impls at all for `Bar`*, because `$0` could be
/// bound to some type that in a downstream crate that implements
/// `Bar`.
///
/// Outside of coherence, we set this to false because we are only
/// interested in types that the user could actually have written.
/// In other words, we consider `$0: Bar` to be unimplemented if
/// there is no type that the user could *actually name* that
/// would satisfy it. This avoids crippling inference, basically.
pub intercrate: bool,
next_trait_solver: bool,
pub obligation_inspector: Cell<Option<ObligationInspector<'tcx>>>,
}
/// See the `error_reporting` module for more details.
#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
pub enum ValuePairs<'tcx> {
Regions(ExpectedFound<ty::Region<'tcx>>),
Terms(ExpectedFound<ty::Term<'tcx>>),
Aliases(ExpectedFound<ty::AliasTerm<'tcx>>),
TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
PolySigs(ExpectedFound<ty::PolyFnSig<'tcx>>),
ExistentialTraitRef(ExpectedFound<ty::PolyExistentialTraitRef<'tcx>>),
ExistentialProjection(ExpectedFound<ty::PolyExistentialProjection<'tcx>>),
Dummy,
}
impl<'tcx> ValuePairs<'tcx> {
pub fn ty(&self) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
if let ValuePairs::Terms(ExpectedFound { expected, found }) = self
&& let Some(expected) = expected.as_type()
&& let Some(found) = found.as_type()
{
Some((expected, found))
} else {
None
}
}
}
/// The trace designates the path through inference that we took to
/// encounter an error or subtyping constraint.
///
/// See the `error_reporting` module for more details.
#[derive(Clone, Debug)]
pub struct TypeTrace<'tcx> {
pub cause: ObligationCause<'tcx>,
pub values: ValuePairs<'tcx>,
}
/// The origin of a `r1 <= r2` constraint.
///
/// See `error_reporting` module for more details
#[derive(Clone, Debug)]
pub enum SubregionOrigin<'tcx> {
/// Arose from a subtyping relation
Subtype(Box<TypeTrace<'tcx>>),
/// When casting `&'a T` to an `&'b Trait` object,
/// relating `'a` to `'b`.
RelateObjectBound(Span),
/// Some type parameter was instantiated with the given type,
/// and that type must outlive some region.
RelateParamBound(Span, Ty<'tcx>, Option<Span>),
/// The given region parameter was instantiated with a region
/// that must outlive some other region.
RelateRegionParamBound(Span, Option<Ty<'tcx>>),
/// Creating a pointer `b` to contents of another reference.
Reborrow(Span),
/// (&'a &'b T) where a >= b
ReferenceOutlivesReferent(Ty<'tcx>, Span),
/// Comparing the signature and requirements of an impl method against
/// the containing trait.
CompareImplItemObligation {
span: Span,
impl_item_def_id: LocalDefId,
trait_item_def_id: DefId,
},
/// Checking that the bounds of a trait's associated type hold for a given impl.
CheckAssociatedTypeBounds {
parent: Box<SubregionOrigin<'tcx>>,
impl_item_def_id: LocalDefId,
trait_item_def_id: DefId,
},
AscribeUserTypeProvePredicate(Span),
}
// `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
#[cfg(target_pointer_width = "64")]
rustc_data_structures::static_assert_size!(SubregionOrigin<'_>, 32);
impl<'tcx> SubregionOrigin<'tcx> {
pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> {
match self {
Self::Subtype(type_trace) => type_trace.cause.to_constraint_category(),
Self::AscribeUserTypeProvePredicate(span) => ConstraintCategory::Predicate(*span),
_ => ConstraintCategory::BoringNoLocation,
}
}
}
/// Times when we replace bound regions with existentials:
#[derive(Clone, Copy, Debug)]
pub enum BoundRegionConversionTime {
/// when a fn is called
FnCall,
/// when two higher-ranked types are compared
HigherRankedType,
/// when projecting an associated type
AssocTypeProjection(DefId),
}
/// Reasons to create a region inference variable.
///
/// See `error_reporting` module for more details.
#[derive(Copy, Clone, Debug)]
pub enum RegionVariableOrigin {
/// Region variables created for ill-categorized reasons.
///
/// They mostly indicate places in need of refactoring.
MiscVariable(Span),
/// Regions created by a `&P` or `[...]` pattern.
PatternRegion(Span),
/// Regions created by `&` operator.
///
AddrOfRegion(Span),
/// Regions created as part of an autoref of a method receiver.
Autoref(Span),
/// Regions created as part of an automatic coercion.
Coercion(Span),
/// Region variables created as the values for early-bound regions.
///
/// FIXME(@lcnr): This should also store a `DefId`, similar to
/// `TypeVariableOrigin`.
RegionParameterDefinition(Span, Symbol),
/// Region variables created when instantiating a binder with
/// existential variables, e.g. when calling a function or method.
BoundRegion(Span, ty::BoundRegionKind, BoundRegionConversionTime),
UpvarRegion(ty::UpvarId, Span),
/// This origin is used for the inference variables that we create
/// during NLL region processing.
Nll(NllRegionVariableOrigin),
}
#[derive(Copy, Clone, Debug)]
pub enum NllRegionVariableOrigin {
/// During NLL region processing, we create variables for free
/// regions that we encounter in the function signature and
/// elsewhere. This origin indices we've got one of those.
FreeRegion,
/// "Universal" instantiation of a higher-ranked region (e.g.,
/// from a `for<'a> T` binder). Meant to represent "any region".
Placeholder(ty::PlaceholderRegion),
Existential {
/// If this is true, then this variable was created to represent a lifetime
/// bound in a `for` binder. For example, it might have been created to
/// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`.
/// Such variables are created when we are trying to figure out if there
/// is any valid instantiation of `'a` that could fit into some scenario.
///
/// This is used to inform error reporting: in the case that we are trying to
/// determine whether there is any valid instantiation of a `'a` variable that meets
/// some constraint C, we want to blame the "source" of that `for` type,
/// rather than blaming the source of the constraint C.
from_forall: bool,
},
}
// FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
#[derive(Copy, Clone, Debug)]
pub enum FixupError {
UnresolvedIntTy(IntVid),
UnresolvedFloatTy(FloatVid),
UnresolvedTy(TyVid),
UnresolvedConst(ConstVid),
UnresolvedEffect(EffectVid),
}
/// See the `region_obligations` field for more information.
#[derive(Clone, Debug)]
pub struct RegionObligation<'tcx> {
pub sub_region: ty::Region<'tcx>,
pub sup_type: Ty<'tcx>,
pub origin: SubregionOrigin<'tcx>,
}
impl fmt::Display for FixupError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
use self::FixupError::*;
match *self {
UnresolvedIntTy(_) => write!(
f,
"cannot determine the type of this integer; \
add a suffix to specify the type explicitly"
),
UnresolvedFloatTy(_) => write!(
f,
"cannot determine the type of this number; \
add a suffix to specify the type explicitly"
),
UnresolvedTy(_) => write!(f, "unconstrained type"),
UnresolvedConst(_) => write!(f, "unconstrained const value"),
UnresolvedEffect(_) => write!(f, "unconstrained effect value"),
}
}
}
/// Used to configure inference contexts before their creation.
pub struct InferCtxtBuilder<'tcx> {
tcx: TyCtxt<'tcx>,
defining_opaque_types: &'tcx ty::List<LocalDefId>,
considering_regions: bool,
skip_leak_check: bool,
/// Whether we are in coherence mode.
intercrate: bool,
/// Whether we should use the new trait solver in the local inference context,
/// which affects things like which solver is used in `predicate_may_hold`.
next_trait_solver: bool,
}
#[extension(pub trait TyCtxtInferExt<'tcx>)]
impl<'tcx> TyCtxt<'tcx> {
fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
InferCtxtBuilder {
tcx: self,
defining_opaque_types: ty::List::empty(),
considering_regions: true,
skip_leak_check: false,
intercrate: false,
next_trait_solver: self.next_trait_solver_globally(),
}
}
}
impl<'tcx> InferCtxtBuilder<'tcx> {
/// Whenever the `InferCtxt` should be able to handle defining uses of opaque types,
/// you need to call this function. Otherwise the opaque type will be treated opaquely.
///
/// It is only meant to be called in two places, for typeck
/// (via `Inherited::build`) and for the inference context used
/// in mir borrowck.
pub fn with_opaque_type_inference(mut self, defining_anchor: LocalDefId) -> Self {
self.defining_opaque_types = self.tcx.opaque_types_defined_by(defining_anchor);
self
}
pub fn with_defining_opaque_types(
mut self,
defining_opaque_types: &'tcx ty::List<LocalDefId>,
) -> Self {
self.defining_opaque_types = defining_opaque_types;
self
}
pub fn with_next_trait_solver(mut self, next_trait_solver: bool) -> Self {
self.next_trait_solver = next_trait_solver;
self
}
pub fn intercrate(mut self, intercrate: bool) -> Self {
self.intercrate = intercrate;
self
}
pub fn ignoring_regions(mut self) -> Self {
self.considering_regions = false;
self
}
pub fn skip_leak_check(mut self, skip_leak_check: bool) -> Self {
self.skip_leak_check = skip_leak_check;
self
}
/// Given a canonical value `C` as a starting point, create an
/// inference context that contains each of the bound values
/// within instantiated as a fresh variable. The `f` closure is
/// invoked with the new infcx, along with the instantiated value
/// `V` and a instantiation `S`. This instantiation `S` maps from
/// the bound values in `C` to their instantiated values in `V`
/// (in other words, `S(C) = V`).
pub fn build_with_canonical<T>(
self,
span: Span,
canonical: &Canonical<'tcx, T>,
) -> (InferCtxt<'tcx>, T, CanonicalVarValues<'tcx>)
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
let infcx = self.with_defining_opaque_types(canonical.defining_opaque_types).build();
let (value, args) = infcx.instantiate_canonical(span, canonical);
(infcx, value, args)
}
pub fn build(&mut self) -> InferCtxt<'tcx> {
let InferCtxtBuilder {
tcx,
defining_opaque_types,
considering_regions,
skip_leak_check,
intercrate,
next_trait_solver,
} = *self;
InferCtxt {
tcx,
defining_opaque_types,
considering_regions,
skip_leak_check,
inner: RefCell::new(InferCtxtInner::new()),
lexical_region_resolutions: RefCell::new(None),
selection_cache: Default::default(),
evaluation_cache: Default::default(),
reported_trait_errors: Default::default(),
reported_signature_mismatch: Default::default(),
tainted_by_errors: Cell::new(None),
err_count_on_creation: tcx.dcx().err_count_excluding_lint_errs(),
universe: Cell::new(ty::UniverseIndex::ROOT),
intercrate,
next_trait_solver,
obligation_inspector: Cell::new(None),
}
}
}
impl<'tcx, T> InferOk<'tcx, T> {
/// Extracts `value`, registering any obligations into `fulfill_cx`.
pub fn into_value_registering_obligations<E: 'tcx>(
self,
infcx: &InferCtxt<'tcx>,
fulfill_cx: &mut dyn TraitEngine<'tcx, E>,
) -> T {
let InferOk { value, obligations } = self;
fulfill_cx.register_predicate_obligations(infcx, obligations);
value
}
}
impl<'tcx> InferOk<'tcx, ()> {
pub fn into_obligations(self) -> Vec<PredicateObligation<'tcx>> {
self.obligations
}
}
impl<'tcx> InferCtxt<'tcx> {
pub fn dcx(&self) -> DiagCtxtHandle<'_> {
self.tcx.dcx().taintable_handle(&self.tainted_by_errors)
}
pub fn defining_opaque_types(&self) -> &'tcx ty::List<LocalDefId> {
self.defining_opaque_types
}
pub fn next_trait_solver(&self) -> bool {
self.next_trait_solver
}
pub fn freshen<T: TypeFoldable<TyCtxt<'tcx>>>(&self, t: T) -> T {
t.fold_with(&mut self.freshener())
}
/// Returns the origin of the type variable identified by `vid`.
///
/// No attempt is made to resolve `vid` to its root variable.
pub fn type_var_origin(&self, vid: TyVid) -> TypeVariableOrigin {
self.inner.borrow_mut().type_variables().var_origin(vid)
}
/// Returns the origin of the const variable identified by `vid`
// FIXME: We should store origins separately from the unification table
// so this doesn't need to be optional.
pub fn const_var_origin(&self, vid: ConstVid) -> Option<ConstVariableOrigin> {
match self.inner.borrow_mut().const_unification_table().probe_value(vid) {
ConstVariableValue::Known { .. } => None,
ConstVariableValue::Unknown { origin, .. } => Some(origin),
}
}
pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
freshen::TypeFreshener::new(self)
}
pub fn unresolved_variables(&self) -> Vec<Ty<'tcx>> {
let mut inner = self.inner.borrow_mut();
let mut vars: Vec<Ty<'_>> = inner
.type_variables()
.unresolved_variables()
.into_iter()
.map(|t| Ty::new_var(self.tcx, t))
.collect();
vars.extend(
(0..inner.int_unification_table().len())
.map(|i| ty::IntVid::from_usize(i))
.filter(|&vid| inner.int_unification_table().probe_value(vid).is_unknown())
.map(|v| Ty::new_int_var(self.tcx, v)),
);
vars.extend(
(0..inner.float_unification_table().len())
.map(|i| ty::FloatVid::from_usize(i))
.filter(|&vid| inner.float_unification_table().probe_value(vid).is_unknown())
.map(|v| Ty::new_float_var(self.tcx, v)),
);
vars
}
pub fn unsolved_effects(&self) -> Vec<ty::Const<'tcx>> {
let mut inner = self.inner.borrow_mut();
let mut table = inner.effect_unification_table();
(0..table.len())
.map(|i| ty::EffectVid::from_usize(i))
.filter(|&vid| table.probe_value(vid).is_unknown())
.map(|v| ty::Const::new_infer(self.tcx, ty::InferConst::EffectVar(v)))
.collect()
}
#[instrument(skip(self), level = "debug")]
pub fn sub_regions(
&self,
origin: SubregionOrigin<'tcx>,
a: ty::Region<'tcx>,
b: ty::Region<'tcx>,
) {
self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
}
/// Require that the region `r` be equal to one of the regions in
/// the set `regions`.
#[instrument(skip(self), level = "debug")]
pub fn member_constraint(
&self,
key: ty::OpaqueTypeKey<'tcx>,
definition_span: Span,
hidden_ty: Ty<'tcx>,
region: ty::Region<'tcx>,
in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
) {
self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
key,
definition_span,
hidden_ty,
region,
in_regions,
);
}
/// Processes a `Coerce` predicate from the fulfillment context.
/// This is NOT the preferred way to handle coercion, which is to
/// invoke `FnCtxt::coerce` or a similar method (see `coercion.rs`).
///
/// This method here is actually a fallback that winds up being
/// invoked when `FnCtxt::coerce` encounters unresolved type variables
/// and records a coercion predicate. Presently, this method is equivalent
/// to `subtype_predicate` -- that is, "coercing" `a` to `b` winds up
/// actually requiring `a <: b`. This is of course a valid coercion,
/// but it's not as flexible as `FnCtxt::coerce` would be.
///
/// (We may refactor this in the future, but there are a number of
/// practical obstacles. Among other things, `FnCtxt::coerce` presently
/// records adjustments that are required on the HIR in order to perform
/// the coercion, and we don't currently have a way to manage that.)
pub fn coerce_predicate(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
predicate: ty::PolyCoercePredicate<'tcx>,
) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
a_is_expected: false, // when coercing from `a` to `b`, `b` is expected
a: p.a,
b: p.b,
});
self.subtype_predicate(cause, param_env, subtype_predicate)
}
pub fn subtype_predicate(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
predicate: ty::PolySubtypePredicate<'tcx>,
) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
// Check for two unresolved inference variables, in which case we can
// make no progress. This is partly a micro-optimization, but it's
// also an opportunity to "sub-unify" the variables. This isn't
// *necessary* to prevent cycles, because they would eventually be sub-unified
// anyhow during generalization, but it helps with diagnostics (we can detect
// earlier that they are sub-unified).
//
// Note that we can just skip the binders here because
// type variables can't (at present, at
// least) capture any of the things bound by this binder.
//
// Note that this sub here is not just for diagnostics - it has semantic
// effects as well.
let r_a = self.shallow_resolve(predicate.skip_binder().a);
let r_b = self.shallow_resolve(predicate.skip_binder().b);
match (r_a.kind(), r_b.kind()) {
(&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
return Err((a_vid, b_vid));
}
_ => {}
}
self.enter_forall(predicate, |ty::SubtypePredicate { a_is_expected, a, b }| {
if a_is_expected {
Ok(self.at(cause, param_env).sub(DefineOpaqueTypes::Yes, a, b))
} else {
Ok(self.at(cause, param_env).sup(DefineOpaqueTypes::Yes, b, a))
}
})
}
pub fn region_outlives_predicate(
&self,
cause: &traits::ObligationCause<'tcx>,
predicate: ty::PolyRegionOutlivesPredicate<'tcx>,
) {
self.enter_forall(predicate, |ty::OutlivesPredicate(r_a, r_b)| {
let origin = SubregionOrigin::from_obligation_cause(cause, || {
RelateRegionParamBound(cause.span, None)
});
self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
})
}
/// Number of type variables created so far.
pub fn num_ty_vars(&self) -> usize {
self.inner.borrow_mut().type_variables().num_vars()
}
pub fn next_ty_var(&self, span: Span) -> Ty<'tcx> {
self.next_ty_var_with_origin(TypeVariableOrigin { span, param_def_id: None })
}
pub fn next_ty_var_with_origin(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
let vid = self.inner.borrow_mut().type_variables().new_var(self.universe(), origin);
Ty::new_var(self.tcx, vid)
}
pub fn next_ty_var_id_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> TyVid {
let origin = TypeVariableOrigin { span, param_def_id: None };
self.inner.borrow_mut().type_variables().new_var(universe, origin)
}
pub fn next_ty_var_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> Ty<'tcx> {
let vid = self.next_ty_var_id_in_universe(span, universe);
Ty::new_var(self.tcx, vid)
}
pub fn next_const_var(&self, span: Span) -> ty::Const<'tcx> {
self.next_const_var_with_origin(ConstVariableOrigin { span, param_def_id: None })
}
pub fn next_const_var_with_origin(&self, origin: ConstVariableOrigin) -> ty::Const<'tcx> {
let vid = self
.inner
.borrow_mut()
.const_unification_table()
.new_key(ConstVariableValue::Unknown { origin, universe: self.universe() })
.vid;
ty::Const::new_var(self.tcx, vid)
}
pub fn next_const_var_in_universe(
&self,
span: Span,
universe: ty::UniverseIndex,
) -> ty::Const<'tcx> {
let origin = ConstVariableOrigin { span, param_def_id: None };
let vid = self
.inner
.borrow_mut()
.const_unification_table()
.new_key(ConstVariableValue::Unknown { origin, universe })
.vid;
ty::Const::new_var(self.tcx, vid)
}
pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid {
self.inner
.borrow_mut()
.const_unification_table()
.new_key(ConstVariableValue::Unknown { origin, universe: self.universe() })
.vid
}
fn next_int_var_id(&self) -> IntVid {
self.inner.borrow_mut().int_unification_table().new_key(ty::IntVarValue::Unknown)
}
pub fn next_int_var(&self) -> Ty<'tcx> {
Ty::new_int_var(self.tcx, self.next_int_var_id())
}
fn next_float_var_id(&self) -> FloatVid {
self.inner.borrow_mut().float_unification_table().new_key(ty::FloatVarValue::Unknown)
}
pub fn next_float_var(&self) -> Ty<'tcx> {
Ty::new_float_var(self.tcx, self.next_float_var_id())
}
/// Creates a fresh region variable with the next available index.
/// The variable will be created in the maximum universe created
/// thus far, allowing it to name any region created thus far.
pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
self.next_region_var_in_universe(origin, self.universe())
}
/// Creates a fresh region variable with the next available index
/// in the given universe; typically, you can use
/// `next_region_var` and just use the maximal universe.
pub fn next_region_var_in_universe(
&self,
origin: RegionVariableOrigin,
universe: ty::UniverseIndex,
) -> ty::Region<'tcx> {
let region_var =
self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin);
ty::Region::new_var(self.tcx, region_var)
}
/// Return the universe that the region `r` was created in. For
/// most regions (e.g., `'static`, named regions from the user,
/// etc) this is the root universe U0. For inference variables or
/// placeholders, however, it will return the universe which they
/// are associated.
pub fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex {
self.inner.borrow_mut().unwrap_region_constraints().universe(r)
}
/// Number of region variables created so far.
pub fn num_region_vars(&self) -> usize {
self.inner.borrow_mut().unwrap_region_constraints().num_region_vars()
}
/// Just a convenient wrapper of `next_region_var` for using during NLL.
#[instrument(skip(self), level = "debug")]
pub fn next_nll_region_var(&self, origin: NllRegionVariableOrigin) -> ty::Region<'tcx> {
self.next_region_var(RegionVariableOrigin::Nll(origin))
}
/// Just a convenient wrapper of `next_region_var` for using during NLL.
#[instrument(skip(self), level = "debug")]
pub fn next_nll_region_var_in_universe(
&self,
origin: NllRegionVariableOrigin,
universe: ty::UniverseIndex,
) -> ty::Region<'tcx> {
self.next_region_var_in_universe(RegionVariableOrigin::Nll(origin), universe)
}
pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
match param.kind {
GenericParamDefKind::Lifetime => {
// Create a region inference variable for the given
// region parameter definition.
self.next_region_var(RegionParameterDefinition(span, param.name)).into()
}
GenericParamDefKind::Type { .. } => {
// Create a type inference variable for the given
// type parameter definition. The generic parameters are
// for actual parameters that may be referred to by
// the default of this type parameter, if it exists.
// e.g., `struct Foo<A, B, C = (A, B)>(...);` when
// used in a path such as `Foo::<T, U>::new()` will
// use an inference variable for `C` with `[T, U]`
// as the generic parameters for the default, `(T, U)`.
let ty_var_id = self.inner.borrow_mut().type_variables().new_var(
self.universe(),
TypeVariableOrigin { param_def_id: Some(param.def_id), span },
);
Ty::new_var(self.tcx, ty_var_id).into()
}
GenericParamDefKind::Const { is_host_effect, .. } => {
if is_host_effect {
return self.var_for_effect(param);
}
let origin = ConstVariableOrigin { param_def_id: Some(param.def_id), span };
let const_var_id = self
.inner
.borrow_mut()
.const_unification_table()
.new_key(ConstVariableValue::Unknown { origin, universe: self.universe() })
.vid;
ty::Const::new_var(self.tcx, const_var_id).into()
}
}
}
pub fn var_for_effect(&self, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
let effect_vid =
self.inner.borrow_mut().effect_unification_table().new_key(EffectVarValue::Unknown).vid;
let ty = self
.tcx
.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
debug_assert_eq!(self.tcx.types.bool, ty);
ty::Const::new_infer(self.tcx, ty::InferConst::EffectVar(effect_vid)).into()
}
/// Given a set of generics defined on a type or impl, returns the generic parameters mapping each
/// type/region parameter to a fresh inference variable.
pub fn fresh_args_for_item(&self, span: Span, def_id: DefId) -> GenericArgsRef<'tcx> {
GenericArgs::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
}
/// Returns `true` if errors have been reported since this infcx was
/// created. This is sometimes used as a heuristic to skip
/// reporting errors that often occur as a result of earlier
/// errors, but where it's hard to be 100% sure (e.g., unresolved
/// inference variables, regionck errors).
#[must_use = "this method does not have any side effects"]
pub fn tainted_by_errors(&self) -> Option<ErrorGuaranteed> {
self.tainted_by_errors.get()
}
/// Set the "tainted by errors" flag to true. We call this when we
/// observe an error from a prior pass.
pub fn set_tainted_by_errors(&self, e: ErrorGuaranteed) {
debug!("set_tainted_by_errors(ErrorGuaranteed)");
self.tainted_by_errors.set(Some(e));
}
pub fn region_var_origin(&self, vid: ty::RegionVid) -> RegionVariableOrigin {
let mut inner = self.inner.borrow_mut();
let inner = &mut *inner;
inner.unwrap_region_constraints().var_origin(vid)
}
/// Clone the list of variable regions. This is used only during NLL processing
/// to put the set of region variables into the NLL region context.
pub fn get_region_var_origins(&self) -> VarInfos {
let mut inner = self.inner.borrow_mut();
let (var_infos, data) = inner
.region_constraint_storage
// We clone instead of taking because borrowck still wants to use
// the inference context after calling this for diagnostics
// and the new trait solver.
.clone()
.expect("regions already resolved")
.with_log(&mut inner.undo_log)
.into_infos_and_data();
assert!(data.is_empty());
var_infos
}
#[instrument(level = "debug", skip(self), ret)]
pub fn take_opaque_types(&self) -> opaque_types::OpaqueTypeMap<'tcx> {
std::mem::take(&mut self.inner.borrow_mut().opaque_type_storage.opaque_types)
}
#[instrument(level = "debug", skip(self), ret)]
pub fn clone_opaque_types(&self) -> opaque_types::OpaqueTypeMap<'tcx> {
self.inner.borrow().opaque_type_storage.opaque_types.clone()
}
#[inline(always)]
pub fn can_define_opaque_ty(&self, id: impl Into<DefId>) -> bool {
let Some(id) = id.into().as_local() else { return false };
self.defining_opaque_types.contains(&id)
}
pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
self.resolve_vars_if_possible(t).to_string()
}
/// If `TyVar(vid)` resolves to a type, return that type. Else, return the
/// universe index of `TyVar(vid)`.
pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
use self::type_variable::TypeVariableValue;
match self.inner.borrow_mut().type_variables().probe(vid) {
TypeVariableValue::Known { value } => Ok(value),
TypeVariableValue::Unknown { universe } => Err(universe),
}
}
pub fn shallow_resolve(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
if let ty::Infer(v) = *ty.kind() {
match v {
ty::TyVar(v) => {
// Not entirely obvious: if `typ` is a type variable,
// it can be resolved to an int/float variable, which
// can then be recursively resolved, hence the
// recursion. Note though that we prevent type
// variables from unifying to other type variables
// directly (though they may be embedded
// structurally), and we prevent cycles in any case,
// so this recursion should always be of very limited
// depth.
//
// Note: if these two lines are combined into one we get
// dynamic borrow errors on `self.inner`.
let known = self.inner.borrow_mut().type_variables().probe(v).known();
known.map_or(ty, |t| self.shallow_resolve(t))
}
ty::IntVar(v) => {
match self.inner.borrow_mut().int_unification_table().probe_value(v) {
ty::IntVarValue::IntType(ty) => Ty::new_int(self.tcx, ty),
ty::IntVarValue::UintType(ty) => Ty::new_uint(self.tcx, ty),
ty::IntVarValue::Unknown => ty,
}
}
ty::FloatVar(v) => {
match self.inner.borrow_mut().float_unification_table().probe_value(v) {
ty::FloatVarValue::Known(ty) => Ty::new_float(self.tcx, ty),
ty::FloatVarValue::Unknown => ty,
}
}
ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => ty,
}
} else {
ty
}
}
pub fn shallow_resolve_const(&self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
match ct.kind() {
ty::ConstKind::Infer(infer_ct) => match infer_ct {
InferConst::Var(vid) => self
.inner
.borrow_mut()
.const_unification_table()
.probe_value(vid)
.known()
.unwrap_or(ct),
InferConst::EffectVar(vid) => self
.inner
.borrow_mut()
.effect_unification_table()
.probe_value(vid)
.known()
.unwrap_or(ct),
InferConst::Fresh(_) => ct,
},
ty::ConstKind::Param(_)
| ty::ConstKind::Bound(_, _)
| ty::ConstKind::Placeholder(_)
| ty::ConstKind::Unevaluated(_)
| ty::ConstKind::Value(_, _)
| ty::ConstKind::Error(_)
| ty::ConstKind::Expr(_) => ct,
}
}
pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
self.inner.borrow_mut().type_variables().root_var(var)
}
pub fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid {
self.inner.borrow_mut().const_unification_table().find(var).vid
}
pub fn root_effect_var(&self, var: ty::EffectVid) -> ty::EffectVid {
self.inner.borrow_mut().effect_unification_table().find(var).vid
}
/// Resolves an int var to a rigid int type, if it was constrained to one,
/// or else the root int var in the unification table.
pub fn opportunistic_resolve_int_var(&self, vid: ty::IntVid) -> Ty<'tcx> {
let mut inner = self.inner.borrow_mut();
let value = inner.int_unification_table().probe_value(vid);
match value {
ty::IntVarValue::IntType(ty) => Ty::new_int(self.tcx, ty),
ty::IntVarValue::UintType(ty) => Ty::new_uint(self.tcx, ty),
ty::IntVarValue::Unknown => {
Ty::new_int_var(self.tcx, inner.int_unification_table().find(vid))
}
}
}
/// Resolves a float var to a rigid int type, if it was constrained to one,
/// or else the root float var in the unification table.
pub fn opportunistic_resolve_float_var(&self, vid: ty::FloatVid) -> Ty<'tcx> {
let mut inner = self.inner.borrow_mut();
let value = inner.float_unification_table().probe_value(vid);
match value {
ty::FloatVarValue::Known(ty) => Ty::new_float(self.tcx, ty),
ty::FloatVarValue::Unknown => {
Ty::new_float_var(self.tcx, inner.float_unification_table().find(vid))
}
}
}
/// Where possible, replaces type/const variables in
/// `value` with their final value. Note that region variables
/// are unaffected. If a type/const variable has not been unified, it
/// is left as is. This is an idempotent operation that does
/// not affect inference state in any way and so you can do it
/// at will.
pub fn resolve_vars_if_possible<T>(&self, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if let Err(guar) = value.error_reported() {
self.set_tainted_by_errors(guar);
}
if !value.has_non_region_infer() {
return value;
}
let mut r = resolve::OpportunisticVarResolver::new(self);
value.fold_with(&mut r)
}
pub fn resolve_numeric_literals_with_default<T>(&self, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if !value.has_infer() {
return value; // Avoid duplicated type-folding.
}
let mut r = InferenceLiteralEraser { tcx: self.tcx };
value.fold_with(&mut r)
}
pub fn probe_const_var(&self, vid: ty::ConstVid) -> Result<ty::Const<'tcx>, ty::UniverseIndex> {
match self.inner.borrow_mut().const_unification_table().probe_value(vid) {
ConstVariableValue::Known { value } => Ok(value),
ConstVariableValue::Unknown { origin: _, universe } => Err(universe),
}
}
pub fn probe_effect_var(&self, vid: EffectVid) -> Option<ty::Const<'tcx>> {
self.inner.borrow_mut().effect_unification_table().probe_value(vid).known()
}
/// Attempts to resolve all type/region/const variables in
/// `value`. Region inference must have been run already (e.g.,
/// by calling `resolve_regions_and_report_errors`). If some
/// variable was never unified, an `Err` results.
///
/// This method is idempotent, but it not typically not invoked
/// except during the writeback phase.
pub fn fully_resolve<T: TypeFoldable<TyCtxt<'tcx>>>(&self, value: T) -> FixupResult<T> {
match resolve::fully_resolve(self, value) {
Ok(value) => {
if value.has_non_region_infer() {
bug!("`{value:?}` is not fully resolved");
}
if value.has_infer_regions() {
let guar = self.dcx().delayed_bug(format!("`{value:?}` is not fully resolved"));
Ok(self.tcx.fold_regions(value, |re, _| {
if re.is_var() { ty::Region::new_error(self.tcx, guar) } else { re }
}))
} else {
Ok(value)
}
}
Err(e) => Err(e),
}
}
// Instantiates the bound variables in a given binder with fresh inference
// variables in the current universe.
//
// Use this method if you'd like to find some generic parameters of the binder's
// variables (e.g. during a method call). If there isn't a [`BoundRegionConversionTime`]
// that corresponds to your use case, consider whether or not you should
// use [`InferCtxt::enter_forall`] instead.
pub fn instantiate_binder_with_fresh_vars<T>(
&self,
span: Span,
lbrct: BoundRegionConversionTime,
value: ty::Binder<'tcx, T>,
) -> T
where
T: TypeFoldable<TyCtxt<'tcx>> + Copy,
{
if let Some(inner) = value.no_bound_vars() {
return inner;
}
let bound_vars = value.bound_vars();
let mut args = Vec::with_capacity(bound_vars.len());
for bound_var_kind in bound_vars {
let arg: ty::GenericArg<'_> = match bound_var_kind {
ty::BoundVariableKind::Ty(_) => self.next_ty_var(span).into(),
ty::BoundVariableKind::Region(br) => {
self.next_region_var(BoundRegion(span, br, lbrct)).into()
}
ty::BoundVariableKind::Const => self.next_const_var(span).into(),
};
args.push(arg);
}
struct ToFreshVars<'tcx> {
args: Vec<ty::GenericArg<'tcx>>,
}
impl<'tcx> BoundVarReplacerDelegate<'tcx> for ToFreshVars<'tcx> {
fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> {
self.args[br.var.index()].expect_region()
}
fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> {
self.args[bt.var.index()].expect_ty()
}
fn replace_const(&mut self, bv: ty::BoundVar) -> ty::Const<'tcx> {
self.args[bv.index()].expect_const()
}
}
let delegate = ToFreshVars { args };
self.tcx.replace_bound_vars_uncached(value, delegate)
}
/// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method.
pub fn verify_generic_bound(
&self,
origin: SubregionOrigin<'tcx>,
kind: GenericKind<'tcx>,
a: ty::Region<'tcx>,
bound: VerifyBound<'tcx>,
) {
debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
self.inner
.borrow_mut()
.unwrap_region_constraints()
.verify_generic_bound(origin, kind, a, bound);
}
/// Obtains the latest type of the given closure; this may be a
/// closure in the current function, in which case its
/// `ClosureKind` may not yet be known.
pub fn closure_kind(&self, closure_ty: Ty<'tcx>) -> Option<ty::ClosureKind> {
let unresolved_kind_ty = match *closure_ty.kind() {
ty::Closure(_, args) => args.as_closure().kind_ty(),
ty::CoroutineClosure(_, args) => args.as_coroutine_closure().kind_ty(),
_ => bug!("unexpected type {closure_ty}"),
};
let closure_kind_ty = self.shallow_resolve(unresolved_kind_ty);
closure_kind_ty.to_opt_closure_kind()
}
pub fn universe(&self) -> ty::UniverseIndex {
self.universe.get()
}
/// Creates and return a fresh universe that extends all previous
/// universes. Updates `self.universe` to that new universe.
pub fn create_next_universe(&self) -> ty::UniverseIndex {
let u = self.universe.get().next_universe();
debug!("create_next_universe {u:?}");
self.universe.set(u);
u
}
pub fn try_const_eval_resolve(
&self,
param_env: ty::ParamEnv<'tcx>,
unevaluated: ty::UnevaluatedConst<'tcx>,
span: Span,
) -> Result<ty::Const<'tcx>, ErrorHandled> {
match self.const_eval_resolve(param_env, unevaluated, span) {
Ok(Ok(val)) => Ok(ty::Const::new_value(
self.tcx,
val,
self.tcx.type_of(unevaluated.def).instantiate(self.tcx, unevaluated.args),
)),
Ok(Err(bad_ty)) => {
let tcx = self.tcx;
let def_id = unevaluated.def;
span_bug!(
tcx.def_span(def_id),
"unable to construct a valtree for the unevaluated constant {:?}: type {bad_ty} is not valtree-compatible",
unevaluated
);
}
Err(err) => Err(err),
}
}
/// Resolves and evaluates a constant.
///
/// The constant can be located on a trait like `<A as B>::C`, in which case the given
/// generic parameters and environment are used to resolve the constant. Alternatively if the
/// constant has generic parameters in scope the instantiations are used to evaluate the value of
/// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
/// constant `bar::<T>()` requires a instantiation for `T`, if the instantiation for `T` is still
/// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
/// returned.
///
/// This handles inferences variables within both `param_env` and `args` by
/// performing the operation on their respective canonical forms.
#[instrument(skip(self), level = "debug")]
pub fn const_eval_resolve(
&self,
mut param_env: ty::ParamEnv<'tcx>,
unevaluated: ty::UnevaluatedConst<'tcx>,
span: Span,
) -> EvalToValTreeResult<'tcx> {
let mut args = self.resolve_vars_if_possible(unevaluated.args);
debug!(?args);
// Postpone the evaluation of constants whose args depend on inference
// variables
let tcx = self.tcx;
if args.has_non_region_infer() {
if let Some(ct) = tcx.thir_abstract_const(unevaluated.def)? {
let ct = tcx.expand_abstract_consts(ct.instantiate(tcx, args));
if let Err(e) = ct.error_reported() {
return Err(ErrorHandled::Reported(e.into(), span));
} else if ct.has_non_region_infer() || ct.has_non_region_param() {
return Err(ErrorHandled::TooGeneric(span));
} else {
args = replace_param_and_infer_args_with_placeholder(tcx, args);
}
} else {
args = GenericArgs::identity_for_item(tcx, unevaluated.def);
param_env = tcx.param_env(unevaluated.def);
}
}
let param_env_erased = tcx.erase_regions(param_env);
let args_erased = tcx.erase_regions(args);
debug!(?param_env_erased);
debug!(?args_erased);
let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, args: args_erased };
// The return value is the evaluated value which doesn't contain any reference to inference
// variables, thus we don't need to instantiate back the original values.
tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
}
/// The returned function is used in a fast path. If it returns `true` the variable is
/// unchanged, `false` indicates that the status is unknown.
#[inline]
pub fn is_ty_infer_var_definitely_unchanged<'a>(
&'a self,
) -> (impl Fn(TyOrConstInferVar) -> bool + Captures<'tcx> + 'a) {
// This hoists the borrow/release out of the loop body.
let inner = self.inner.try_borrow();
return move |infer_var: TyOrConstInferVar| match (infer_var, &inner) {
(TyOrConstInferVar::Ty(ty_var), Ok(inner)) => {
use self::type_variable::TypeVariableValue;
matches!(
inner.try_type_variables_probe_ref(ty_var),
Some(TypeVariableValue::Unknown { .. })
)
}
_ => false,
};
}
/// `ty_or_const_infer_var_changed` is equivalent to one of these two:
/// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`)
/// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`)
///
/// However, `ty_or_const_infer_var_changed` is more efficient. It's always
/// inlined, despite being large, because it has only two call sites that
/// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on`
/// inference variables), and it handles both `Ty` and `ty::Const` without
/// having to resort to storing full `GenericArg`s in `stalled_on`.
#[inline(always)]
pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar) -> bool {
match infer_var {
TyOrConstInferVar::Ty(v) => {
use self::type_variable::TypeVariableValue;
// If `inlined_probe` returns a `Known` value, it never equals
// `ty::Infer(ty::TyVar(v))`.
match self.inner.borrow_mut().type_variables().inlined_probe(v) {
TypeVariableValue::Unknown { .. } => false,
TypeVariableValue::Known { .. } => true,
}
}
TyOrConstInferVar::TyInt(v) => {
// If `inlined_probe_value` returns a value it's always a
// `ty::Int(_)` or `ty::UInt(_)`, which never matches a
// `ty::Infer(_)`.
self.inner.borrow_mut().int_unification_table().inlined_probe_value(v).is_known()
}
TyOrConstInferVar::TyFloat(v) => {
// If `probe_value` returns a value it's always a
// `ty::Float(_)`, which never matches a `ty::Infer(_)`.
//
// Not `inlined_probe_value(v)` because this call site is colder.
self.inner.borrow_mut().float_unification_table().probe_value(v).is_known()
}
TyOrConstInferVar::Const(v) => {
// If `probe_value` returns a `Known` value, it never equals
// `ty::ConstKind::Infer(ty::InferConst::Var(v))`.
//
// Not `inlined_probe_value(v)` because this call site is colder.
match self.inner.borrow_mut().const_unification_table().probe_value(v) {
ConstVariableValue::Unknown { .. } => false,
ConstVariableValue::Known { .. } => true,
}
}
TyOrConstInferVar::Effect(v) => {
// If `probe_value` returns `Some`, it never equals
// `ty::ConstKind::Infer(ty::InferConst::Effect(v))`.
//
// Not `inlined_probe_value(v)` because this call site is colder.
self.probe_effect_var(v).is_some()
}
}
}
/// Attach a callback to be invoked on each root obligation evaluated in the new trait solver.
pub fn attach_obligation_inspector(&self, inspector: ObligationInspector<'tcx>) {
debug_assert!(
self.obligation_inspector.get().is_none(),
"shouldn't override a set obligation inspector"
);
self.obligation_inspector.set(Some(inspector));
}
}
/// Helper for [InferCtxt::ty_or_const_infer_var_changed] (see comment on that), currently
/// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
#[derive(Copy, Clone, Debug)]
pub enum TyOrConstInferVar {
/// Equivalent to `ty::Infer(ty::TyVar(_))`.
Ty(TyVid),
/// Equivalent to `ty::Infer(ty::IntVar(_))`.
TyInt(IntVid),
/// Equivalent to `ty::Infer(ty::FloatVar(_))`.
TyFloat(FloatVid),
/// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
Const(ConstVid),
/// Equivalent to `ty::ConstKind::Infer(ty::InferConst::EffectVar(_))`.
Effect(EffectVid),
}
impl<'tcx> TyOrConstInferVar {
/// Tries to extract an inference variable from a type or a constant, returns `None`
/// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
/// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option<Self> {
match arg.unpack() {
GenericArgKind::Type(ty) => Self::maybe_from_ty(ty),
GenericArgKind::Const(ct) => Self::maybe_from_const(ct),
GenericArgKind::Lifetime(_) => None,
}
}
/// Tries to extract an inference variable from a type, returns `None`
/// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
match *ty.kind() {
ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)),
_ => None,
}
}
/// Tries to extract an inference variable from a constant, returns `None`
/// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
fn maybe_from_const(ct: ty::Const<'tcx>) -> Option<Self> {
match ct.kind() {
ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
ty::ConstKind::Infer(InferConst::EffectVar(v)) => Some(TyOrConstInferVar::Effect(v)),
_ => None,
}
}
}
/// Replace `{integer}` with `i32` and `{float}` with `f64`.
/// Used only for diagnostics.
struct InferenceLiteralEraser<'tcx> {
tcx: TyCtxt<'tcx>,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for InferenceLiteralEraser<'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
match ty.kind() {
ty::Infer(ty::IntVar(_) | ty::FreshIntTy(_)) => self.tcx.types.i32,
ty::Infer(ty::FloatVar(_) | ty::FreshFloatTy(_)) => self.tcx.types.f64,
_ => ty.super_fold_with(self),
}
}
}
impl<'tcx> TypeTrace<'tcx> {
pub fn span(&self) -> Span {
self.cause.span
}
pub fn types(
cause: &ObligationCause<'tcx>,
a_is_expected: bool,
a: Ty<'tcx>,
b: Ty<'tcx>,
) -> TypeTrace<'tcx> {
TypeTrace {
cause: cause.clone(),
values: ValuePairs::Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
}
}
pub fn trait_refs(
cause: &ObligationCause<'tcx>,
a_is_expected: bool,
a: ty::TraitRef<'tcx>,
b: ty::TraitRef<'tcx>,
) -> TypeTrace<'tcx> {
TypeTrace {
cause: cause.clone(),
values: ValuePairs::TraitRefs(ExpectedFound::new(a_is_expected, a, b)),
}
}
pub fn consts(
cause: &ObligationCause<'tcx>,
a_is_expected: bool,
a: ty::Const<'tcx>,
b: ty::Const<'tcx>,
) -> TypeTrace<'tcx> {
TypeTrace {
cause: cause.clone(),
values: ValuePairs::Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
}
}
fn dummy(cause: &ObligationCause<'tcx>) -> TypeTrace<'tcx> {
TypeTrace { cause: cause.clone(), values: ValuePairs::Dummy }
}
}
impl<'tcx> SubregionOrigin<'tcx> {
pub fn span(&self) -> Span {
match *self {
Subtype(ref a) => a.span(),
RelateObjectBound(a) => a,
RelateParamBound(a, ..) => a,
RelateRegionParamBound(a, _) => a,
Reborrow(a) => a,
ReferenceOutlivesReferent(_, a) => a,
CompareImplItemObligation { span, .. } => span,
AscribeUserTypeProvePredicate(span) => span,
CheckAssociatedTypeBounds { ref parent, .. } => parent.span(),
}
}
pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
where
F: FnOnce() -> Self,
{
match *cause.code() {
traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
}
traits::ObligationCauseCode::CompareImplItem {
impl_item_def_id,
trait_item_def_id,
kind: _,
} => SubregionOrigin::CompareImplItemObligation {
span: cause.span,
impl_item_def_id,
trait_item_def_id,
},
traits::ObligationCauseCode::CheckAssociatedTypeBounds {
impl_item_def_id,
trait_item_def_id,
} => SubregionOrigin::CheckAssociatedTypeBounds {
impl_item_def_id,
trait_item_def_id,
parent: Box::new(default()),
},
traits::ObligationCauseCode::AscribeUserTypeProvePredicate(span) => {
SubregionOrigin::AscribeUserTypeProvePredicate(span)
}
traits::ObligationCauseCode::ObjectTypeBound(ty, _reg) => {
SubregionOrigin::RelateRegionParamBound(cause.span, Some(ty))
}
_ => default(),
}
}
}
impl RegionVariableOrigin {
pub fn span(&self) -> Span {
match *self {
MiscVariable(a)
| PatternRegion(a)
| AddrOfRegion(a)
| Autoref(a)
| Coercion(a)
| RegionParameterDefinition(a, ..)
| BoundRegion(a, ..)
| UpvarRegion(_, a) => a,
Nll(..) => bug!("NLL variable used with `span`"),
}
}
}
/// Replaces args that reference param or infer variables with suitable
/// placeholders. This function is meant to remove these param and infer
/// args when they're not actually needed to evaluate a constant.
fn replace_param_and_infer_args_with_placeholder<'tcx>(
tcx: TyCtxt<'tcx>,
args: GenericArgsRef<'tcx>,
) -> GenericArgsRef<'tcx> {
struct ReplaceParamAndInferWithPlaceholder<'tcx> {
tcx: TyCtxt<'tcx>,
idx: u32,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceParamAndInferWithPlaceholder<'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
if let ty::Infer(_) = t.kind() {
let idx = {
let idx = self.idx;
self.idx += 1;
idx
};
Ty::new_placeholder(
self.tcx,
ty::PlaceholderType {
universe: ty::UniverseIndex::ROOT,
bound: ty::BoundTy {
var: ty::BoundVar::from_u32(idx),
kind: ty::BoundTyKind::Anon,
},
},
)
} else {
t.super_fold_with(self)
}
}
fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
if let ty::ConstKind::Infer(_) = c.kind() {
ty::Const::new_placeholder(
self.tcx,
ty::PlaceholderConst {
universe: ty::UniverseIndex::ROOT,
bound: ty::BoundVar::from_u32({
let idx = self.idx;
self.idx += 1;
idx
}),
},
)
} else {
c.super_fold_with(self)
}
}
}
args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: 0 })
}
impl<'tcx> InferCtxt<'tcx> {
/// Given a [`hir::Block`], get the span of its last expression or
/// statement, peeling off any inner blocks.
pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
let block = block.innermost_block();
if let Some(expr) = &block.expr {
expr.span
} else if let Some(stmt) = block.stmts.last() {
// possibly incorrect trailing `;` in the else arm
stmt.span
} else {
// empty block; point at its entirety
block.span
}
}
/// Given a [`hir::HirId`] for a block, get the span of its last expression
/// or statement, peeling off any inner blocks.
pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
match self.tcx.hir_node(hir_id) {
hir::Node::Block(blk) => self.find_block_span(blk),
// The parser was in a weird state if either of these happen, but
// it's better not to panic.
hir::Node::Expr(e) => e.span,
_ => rustc_span::DUMMY_SP,
}
}
}