Struct InferCtxt 

pub struct InferCtxt<'db> {
    pub interner: DbInterner<'db>,
    typing_mode: TypingMode<'db>,
    pub inner: RefCell<InferCtxtInner<'db>>,
    tainted_by_errors: Cell<Option<ErrorGuaranteed>>,
    universe: Cell<UniverseIndex>,
    obligation_inspector: Cell<Option<ObligationInspector<'db>>>,
}

Fields

interner: DbInterner<'db>

typing_mode: TypingMode<'db>

The mode of this inference context, see the struct documentation for more details.

inner: RefCell<InferCtxtInner<'db>>

tainted_by_errors: Cell<Option<ErrorGuaranteed>>

When an error occurs, we want to avoid reporting “derived” errors that are due to this original failure. We have this 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().

universe: Cell<UniverseIndex>

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.

obligation_inspector: Cell<Option<ObligationInspector<'db>>>

Implementations

impl<'db> InferCtxt<'db>

pub fn at<'a>( &'a self, cause: &'a ObligationCause, param_env: ParamEnv<'db>, ) -> At<'a, 'db>

pub fn fork(&self) -> Self

Forks the inference context, creating a new inference context with the same inference variables in the same state. This can be used to “branch off” many tests from the same common state.

pub fn fork_with_typing_mode( &self, typing_mode: TypingMode<DbInterner<'db>>, ) -> Self

Forks the inference context, creating a new inference context with the same inference variables in the same state, except possibly changing the intercrate mode. This can be used to “branch off” many tests from the same common state. Used in negative coherence.

impl<'db> InferCtxt<'db>

pub fn canonicalize_query<V>( &self, value: V, query_state: &mut OriginalQueryValues<'db>, ) -> Canonical<'db, V>

where V: TypeFoldable<DbInterner<'db>>,

Canonicalizes a query value V. When we canonicalize a query, we not only canonicalize unbound inference variables, but we also replace all free regions whatsoever. So for example a query like T: Trait<'static> would be canonicalized to

T: Trait<'?0>

with a mapping M that maps '?0 to 'static.

To get a good understanding of what is happening here, check out the chapter in the rustc dev guide.

pub fn canonicalize_response<V>(&self, value: V) -> Canonical<'db, V>

where V: TypeFoldable<DbInterner<'db>>,

Canonicalizes a query response V. When we canonicalize a query response, we only canonicalize unbound inference variables, and we leave other free regions alone. So, continuing with the example from canonicalize_query, if there was an input query T: Trait<'static>, it would have been canonicalized to

T: Trait<'?0>

with a mapping M that maps '?0 to 'static. But if we found that there exists only one possible impl of Trait, and it looks like

impl<T> Trait<'static> for T { .. }

then we would prepare a query result R that (among other things) includes a mapping to '?0 := 'static. When canonicalizing this query result R, we would leave this reference to 'static alone.

To get a good understanding of what is happening here, check out the chapter in the rustc dev guide.

pub fn canonicalize_user_type_annotation<V>( &self, value: V, ) -> Canonical<'db, V>

where V: TypeFoldable<DbInterner<'db>>,

impl<'db> InferCtxt<'db>

pub fn make_query_response_ignoring_pending_obligations<T>( &self, inference_vars: CanonicalVarValues<'db>, answer: T, prev_entries: OpaqueTypeStorageEntries, ) -> Canonical<'db, QueryResponse<'db, T>>

where T: TypeFoldable<DbInterner<'db>>,

A version of make_canonicalized_query_response that does not pack in obligations, for contexts that want to drop pending obligations instead of treating them as an ambiguity (e.g. typeck “probing” contexts).

If you DO want to keep track of pending obligations (which include all region obligations, so this includes all cases that care about regions) with this function, you have to do it yourself, by e.g., having them be a part of the answer.

pub fn instantiate_query_response_and_region_obligations<R>( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, original_values: &OriginalQueryValues<'db>, query_response: &Canonical<'db, QueryResponse<'db, R>>, ) -> InferResult<'db, R>

where R: TypeFoldable<DbInterner<'db>>,

Given the (canonicalized) result to a canonical query, instantiates the result so it can be used, plugging in the values from the canonical query. (Note that the result may have been ambiguous; you should check the certainty level of the query before applying this function.)

To get a good understanding of what is happening here, check out the chapter in the rustc dev guide.

fn query_response_instantiation<R>( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, original_values: &OriginalQueryValues<'db>, query_response: &Canonical<'db, QueryResponse<'db, R>>, ) -> InferResult<'db, CanonicalVarValues<'db>>

where R: Debug + TypeFoldable<DbInterner<'db>>,

Given the original values and the (canonicalized) result from computing a query, returns an instantiation that can be applied to the query result to convert the result back into the original namespace.

The instantiation also comes accompanied with subobligations that arose from unification; these might occur if (for example) we are doing lazy normalization and the value assigned to a type variable is unified with an unnormalized projection.

fn query_response_instantiation_guess<R>( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, original_values: &OriginalQueryValues<'db>, query_response: &Canonical<'db, QueryResponse<'db, R>>, ) -> InferResult<'db, CanonicalVarValues<'db>>

where R: Debug + TypeFoldable<DbInterner<'db>>,

Given the original values and the (canonicalized) result from computing a query, returns a guess at an instantiation that can be applied to the query result to convert the result back into the original namespace. This is called a guess because it uses a quick heuristic to find the values for each canonical variable; if that quick heuristic fails, then we will instantiate fresh inference variables for each canonical variable instead. Therefore, the result of this method must be properly unified

fn unify_query_response_instantiation_guess<R>( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, original_values: &OriginalQueryValues<'db>, result_args: &CanonicalVarValues<'db>, query_response: &Canonical<'db, QueryResponse<'db, R>>, ) -> InferResult<'db, ()>

where R: Debug + TypeFoldable<DbInterner<'db>>,

Given a “guess” at the values for the canonical variables in the input, try to unify with the actual values found in the query result. Often, but not always, this is a no-op, because we already found the mapping in the “guessing” step.

See also: Self::query_response_instantiation_guess

fn unify_canonical_vars( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, variables1: &OriginalQueryValues<'db>, variables2: impl Fn(BoundVar) -> GenericArg<'db>, ) -> InferResult<'db, ()>

Given two sets of values for the same set of canonical variables, unify them. The second set is produced lazily by supplying indices from the first set.

impl<'db> InferCtxt<'db>

pub fn instantiate_canonical<T>( &self, span: Span, canonical: &Canonical<'db, T>, ) -> (T, CanonicalVarValues<'db>)

where T: TypeFoldable<DbInterner<'db>>,

Creates an instantiation S for the canonical value with fresh inference variables and placeholders then applies it to the canonical value. Returns both the instantiated result and the instantiation S.

This can be invoked as part of constructing an inference context at the start of a query (see InferCtxtBuilder::build_with_canonical). It basically brings the canonical value “into scope” within your new infcx.

At the end of processing, the instantiation S (once canonicalized) then represents the values that you computed for each of the canonical inputs to your query.

pub fn instantiate_canonical_var( &self, span: Span, cv_info: CanonicalVarKind<DbInterner<'db>>, previous_var_values: &[GenericArg<'db>], universe_map: impl Fn(UniverseIndex) -> UniverseIndex, ) -> GenericArg<'db>

Given the “info” about a canonical variable, creates a fresh variable for it. If this is an existentially quantified variable, then you’ll get a new inference variable; if it is a universally quantified variable, you get a placeholder.

FIXME(-Znext-solver): This is public because it’s used by the new trait solver which has a different canonicalization routine. We should somehow deduplicate all of this.

impl<'db> InferCtxt<'db>

pub fn register_hidden_type_in_storage( &self, opaque_type_key: OpaqueTypeKey<'db>, hidden_ty: OpaqueHiddenType<'db>, ) -> Option<Ty<'db>>

Insert a hidden type into the opaque type storage, making sure it hasn’t previously been defined. This does not emit any constraints and it’s the responsibility of the caller to make sure that the item bounds of the opaque are checked.

impl<'db> InferCtxt<'db>

pub fn register_outlives_constraint( &self, OutlivesPredicate: ArgOutlivesPredicate<'db>, )

pub fn register_region_outlives_constraint( &self, OutlivesPredicate: RegionOutlivesPredicate<'db>, )

pub fn register_type_outlives_constraint_inner( &self, obligation: TypeOutlivesConstraint<'db>, )

Registers that the given region obligation must be resolved from within the scope of body_id. These regions are enqueued and later processed by regionck, when full type information is available (see region_obligations field for more information).

pub fn register_type_outlives_constraint( &self, sup_type: Ty<'db>, sub_region: Region<'db>, )

pub fn register_region_assumption(&self, assumption: ArgOutlivesPredicate<'db>)

impl<'db> InferCtxt<'db>

pub fn instantiate_ty_var<R: PredicateEmittingRelation<InferCtxt<'db>>>( &self, relation: &mut R, target_is_expected: bool, target_vid: TyVid, instantiation_variance: Variance, source_ty: Ty<'db>, ) -> RelateResult<'db, ()>

The idea is that we should ensure that the type variable target_vid is equal to, a subtype of, or a supertype of source_ty.

For this, we will instantiate target_vid with a generalized version of source_ty. Generalization introduces other inference variables wherever subtyping could occur. This also does the occurs checks, detecting whether instantiating target_vid would result in a cyclic type. We eagerly error in this case.

This is not expected to be used anywhere except for an implementation of TypeRelation. Do not use this, and instead please use At::eq, for all other usecases (i.e. setting the value of a type var).

pub(crate) fn instantiate_const_var<R: PredicateEmittingRelation<InferCtxt<'db>>>( &self, relation: &mut R, target_is_expected: bool, target_vid: ConstVid, source_ct: Const<'db>, ) -> RelateResult<'db, ()>

Instantiates the const variable target_vid with the given constant.

This also tests if the given const ct contains an inference variable which was previously unioned with target_vid. If this is the case, inferring target_vid to ct would result in an infinite type as we continuously replace an inference variable in ct with ct itself.

This is especially important as unevaluated consts use their parents generics. They therefore often contain unused args, making these errors far more likely.

A good example of this is the following:

#![feature(generic_const_exprs)]

fn bind<const N: usize>(value: [u8; N]) -> [u8; 3 + 4] {
    todo!()
}

fn main() {
    let mut arr = Default::default();
    arr = bind(arr);
}

Here 3 + 4 ends up as ConstKind::Unevaluated which uses the generics of fn bind (meaning that its args contain N).

bind(arr) now infers that the type of arr must be [u8; N]. The assignment arr = bind(arr) now tries to equate N with 3 + 4.

As 3 + 4 contains N in its args, this must not succeed.

See tests/ui/const-generics/occurs-check/ for more examples where this is relevant.

fn generalize<T: Into<Term<'db>> + Relate<DbInterner<'db>>>( &self, span: Span, structurally_relate_aliases: StructurallyRelateAliases, target_vid: impl Into<TermVid>, ambient_variance: Variance, source_term: T, ) -> RelateResult<'db, Generalization<T>>

Attempts to generalize source_term for the type variable target_vid. This checks for cycles – that is, whether source_term references target_vid.

impl<'db> InferCtxt<'db>

pub fn enter_forall_and_leak_universe<T>(&self, binder: Binder<'db, T>) -> T

where T: TypeFoldable<DbInterner<'db>> + Clone,

Replaces all bound variables (lifetimes, types, and constants) bound by binder with placeholder variables in a new universe. This means that the new placeholders can only be named by inference variables created after this method has been called.

This is the first step of checking subtyping when higher-ranked things are involved. For more details visit the relevant sections of the rustc dev guide.

fn enter_forall should be preferred over this method.

pub fn enter_forall<T, U>( &self, forall: Binder<'db, T>, f: impl FnOnce(T) -> U, ) -> U

where T: TypeFoldable<DbInterner<'db>> + Clone,

Replaces all bound variables (lifetimes, types, and constants) bound by binder with placeholder variables in a new universe and then calls the closure f with the instantiated value. The new placeholders can only be named by inference variables created inside of the closure f or afterwards.

This is the first step of checking subtyping when higher-ranked things are involved. For more details visit the relevant sections of the rustc dev guide.

This method should be preferred over fn enter_forall_and_leak_universe.

impl<'db> InferCtxt<'db>

pub(crate) fn select( &self, obligation: &Obligation<'db, TraitPredicate<'db>>, ) -> Result<Option<ImplSource<'db, Obligation<'db, Predicate<'db>>>>, SelectionError<'db>>

impl<'db> InferCtxt<'db>

pub fn fudge_inference_if_ok<T, E, F>(&self, f: F) -> Result<T, E>

where F: FnOnce() -> Result<T, E>, T: TypeFoldable<DbInterner<'db>>,

This rather funky routine is used while processing expected types. What happens here is that we want to propagate a coercion through the return type of a fn to its argument. Consider the type of Option::Some, which is basically for<T> fn(T) -> Option<T>. So if we have an expression Some(&[1, 2, 3]), and that has the expected type Option<&[u32]>, we would like to type check &[1, 2, 3] with the expectation of &[u32]. This will cause us to coerce from &[u32; 3] to &[u32] and make the users life more pleasant.

The way we do this is using fudge_inference_if_ok. What the routine actually does is to start a snapshot and execute the closure f. In our example above, what this closure will do is to unify the expectation (Option<&[u32]>) with the actual return type (Option<?T>, where ?T represents the variable instantiated for T). This will cause ?T to be unified with &?a [u32], where ?a is a fresh lifetime variable. The input type (?T) is then returned by f().

At this point, fudge_inference_if_ok will normalize all type variables, converting ?T to &?a [u32] and end the snapshot. The problem is that we can’t just return this type out, because it references the region variable ?a, and that region variable was popped when we popped the snapshot.

So what we do is to keep a list (region_vars, in the code below) of region variables created during the snapshot (here, ?a). We fold the return value and replace any such regions with a new region variable (e.g., ?b) and return the result (&?b [u32]). This can then be used as the expectation for the fn argument.

The important point here is that, for soundness purposes, the regions in question are not particularly important. We will use the expected types to guide coercions, but we will still type-check the resulting types from those coercions against the actual types (?T, Option<?T>) – and remember that after the snapshot is popped, the variable ?T is no longer unified.

fn fudge_inference<T: TypeFoldable<DbInterner<'db>>>( &self, snapshot_vars: SnapshotVarData, value: T, ) -> T

impl<'db> InferCtxt<'db>

fn variable_lengths(&self) -> VariableLengths

pub fn in_snapshot(&self) -> bool

pub fn num_open_snapshots(&self) -> usize

pub fn start_snapshot(&self) -> CombinedSnapshot

pub fn rollback_to(&self, snapshot: CombinedSnapshot)

pub fn commit_from(&self, snapshot: CombinedSnapshot)

pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>

where F: FnOnce(&CombinedSnapshot) -> Result<T, E>,

Execute f and commit the bindings if closure f returns Ok(_).

pub fn probe<R, F>(&self, f: F) -> R

where F: FnOnce(&CombinedSnapshot) -> R,

Execute f then unroll any bindings it creates.

pub fn region_constraints_added_in_snapshot( &self, snapshot: &CombinedSnapshot, ) -> bool

Scan the constraints produced since snapshot and check whether we added any region constraints.

pub fn opaque_types_added_in_snapshot( &self, snapshot: &CombinedSnapshot, ) -> bool

impl<'db> InferCtxt<'db>

pub fn typing_mode_raw(&self) -> TypingMode<'db>

pub fn typing_mode_unchecked(&self) -> TypingMode<'db>

pub fn predicate_may_hold( &self, obligation: &Obligation<'db, Predicate<'db>>, ) -> bool

Evaluates whether the predicate can be satisfied (by any means) in the given ParamEnv.

pub fn predicate_may_hold_opaque_types_jank( &self, obligation: &Obligation<'db, Predicate<'db>>, ) -> bool

See the comment on GeneralAutoderef::overloaded_deref_ty for more details.

pub(crate) fn insert_type_vars<T>(&self, ty: T) -> T

where T: TypeFoldable<DbInterner<'db>>,

pub fn predicate_must_hold_considering_regions( &self, obligation: &Obligation<'db, Predicate<'db>>, ) -> bool

Evaluates whether the predicate can be satisfied in the given ParamEnv, and returns false if not certain. However, this is not entirely accurate if inference variables are involved.

This version may conservatively fail when outlives obligations are required. Therefore, this version should only be used for optimizations or diagnostics and be treated as if it can always return false.

Example

trait Trait {}

fn check<T: Trait>() {}

fn foo<T: 'static>()
where
    &'static T: Trait,
{
    // Evaluating `&'?0 T: Trait` adds a `'?0: 'static` outlives obligation,
    // which means that `predicate_must_hold_considering_regions` will return
    // `false`.
    check::<&'_ T>();
}

pub fn predicate_must_hold_modulo_regions( &self, obligation: &Obligation<'db, Predicate<'db>>, ) -> bool

Evaluates whether the predicate can be satisfied in the given ParamEnv, and returns false if not certain. However, this is not entirely accurate if inference variables are involved.

This version ignores all outlives constraints.

pub fn type_implements_trait( &self, trait_def_id: TraitId, params: impl IntoIterator<Item: Into<GenericArg<'db>>>, param_env: ParamEnv<'db>, ) -> EvaluationResult

Check whether a ty implements given trait(trait_def_id) without side-effects.

The inputs are:

• the def-id of the trait
• the type parameters of the trait, including the self-type
• the parameter environment

Invokes evaluate_obligation, so in the event that evaluating Ty: Trait causes overflow, EvaluatedToAmbigStackDependent will be returned.

type_implements_trait is a convenience function for simple cases like

let copy_trait = infcx.tcx.require_lang_item(LangItem::Copy, span);
let implements_copy = infcx.type_implements_trait(copy_trait, [ty], param_env)
.must_apply_modulo_regions();

In most cases you should instead create an Obligation and check whether it holds via evaluate_obligation or one of its helper functions like predicate_must_hold_modulo_regions, because it properly handles higher ranked traits and it is more convenient and safer when your params are inside a Binder.

fn evaluate_obligation( &self, obligation: &Obligation<'db, Predicate<'db>>, ) -> EvaluationResult

Evaluate a given predicate, capturing overflow and propagating it back.

pub fn can_eq<T: ToTrace<'db>>( &self, param_env: ParamEnv<'db>, a: T, b: T, ) -> bool

pub fn goal_may_hold_opaque_types_jank( &self, goal: Goal<'db, Predicate<'db>>, ) -> bool

See the comment on GeneralAutoderef::overloaded_deref_ty for more details.

pub fn type_is_copy_modulo_regions( &self, param_env: ParamEnv<'db>, ty: Ty<'db>, ) -> bool

pub fn type_is_sized_modulo_regions( &self, param_env: ParamEnv<'db>, ty: Ty<'db>, ) -> bool

pub fn type_is_use_cloned_modulo_regions( &self, param_env: ParamEnv<'db>, ty: Ty<'db>, ) -> bool

pub fn unresolved_variables(&self) -> Vec<Ty<'db>>

pub fn sub_regions(&self, a: Region<'db>, b: Region<'db>)

pub fn coerce_predicate( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, predicate: PolyCoercePredicate<'db>, ) -> Result<InferResult<'db, ()>, (TyVid, TyVid)>

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 subtype_predicate( &self, cause: &ObligationCause, param_env: ParamEnv<'db>, predicate: PolySubtypePredicate<'db>, ) -> Result<InferResult<'db, ()>, (TyVid, TyVid)>

pub fn region_outlives_predicate( &self, _cause: &ObligationCause, predicate: PolyRegionOutlivesPredicate<'db>, )

pub fn num_ty_vars(&self) -> usize

Number of type variables created so far.

pub fn next_ty_var(&self, span: Span) -> Ty<'db>

pub fn next_ty_vid(&self, span: Span) -> TyVid

pub fn next_ty_var_id_in_universe( &self, universe: UniverseIndex, span: Span, ) -> TyVid

pub fn next_ty_var_in_universe( &self, universe: UniverseIndex, span: Span, ) -> Ty<'db>

pub fn next_const_var(&self, span: Span) -> Const<'db>

pub fn next_const_vid(&self, span: Span) -> ConstVid

pub fn next_const_vid_in_universe( &self, universe: UniverseIndex, span: Span, ) -> ConstVid

pub fn next_const_var_in_universe( &self, universe: UniverseIndex, span: Span, ) -> Const<'db>

pub fn next_int_var(&self) -> Ty<'db>

pub fn next_int_vid(&self) -> IntVid

pub fn next_float_var(&self) -> Ty<'db>

pub fn next_float_vid(&self) -> FloatVid

pub fn next_region_var(&self, span: Span) -> Region<'db>

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_vid(&self, span: Span) -> RegionVid

pub fn next_region_var_in_universe( &self, universe: UniverseIndex, span: Span, ) -> Region<'db>

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_term_var_of_kind(&self, term: Term<'db>, span: Span) -> Term<'db>

pub fn universe_of_region(&self, r: Region<'db>) -> UniverseIndex

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 num_region_vars(&self) -> usize

Number of region variables created so far.

pub fn var_for_def(&self, id: GenericParamId, span: Span) -> GenericArg<'db>

pub fn fresh_args_for_item( &self, span: Span, def_id: SolverDefId<'db>, ) -> GenericArgs<'db>

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 fill_rest_fresh_args( &self, span: Span, def_id: SolverDefId<'db>, first: impl IntoIterator<Item = GenericArg<'db>>, ) -> GenericArgs<'db>

Like Self::fresh_args_for_item, but first uses the args from first.

pub fn tainted_by_errors(&self) -> Option<ErrorGuaranteed>

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).

pub fn set_tainted_by_errors(&self, e: ErrorGuaranteed)

Set the “tainted by errors” flag to true. We call this when we observe an error from a prior pass.

pub fn take_opaque_types( &self, ) -> impl IntoIterator<Item = (OpaqueTypeKey<'db>, OpaqueHiddenType<'db>)> + use<'db>

pub fn clone_opaque_types( &self, ) -> Vec<(OpaqueTypeKey<'db>, OpaqueHiddenType<'db>)>

pub fn has_opaques_with_sub_unified_hidden_type(&self, ty_vid: TyVid) -> bool

pub fn can_define_opaque_ty(&self, id: impl Into<SolverDefId<'db>>) -> bool

pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'db>, UniverseIndex>

If TyVar(vid) resolves to a type, return that type. Else, return the universe index of TyVar(vid).

pub fn shallow_resolve(&self, ty: Ty<'db>) -> Ty<'db>

pub fn shallow_resolve_const(&self, ct: Const<'db>) -> Const<'db>

pub fn shallow_resolve_term(&self, term: Term<'db>) -> Term<'db>

pub fn root_var(&self, var: TyVid) -> TyVid

pub fn root_const_var(&self, var: ConstVid) -> ConstVid

pub fn opportunistic_resolve_int_var(&self, vid: IntVid) -> Ty<'db>

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 resolve_int_var(&self, vid: IntVid) -> Option<Ty<'db>>

pub fn opportunistic_resolve_float_var(&self, vid: FloatVid) -> Ty<'db>

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 resolve_float_var(&self, vid: FloatVid) -> Option<Ty<'db>>

pub fn resolve_vars_if_possible<T>(&self, value: T) -> T

where T: TypeFoldable<DbInterner<'db>>,

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 probe_const_var( &self, vid: ConstVid, ) -> Result<Const<'db>, UniverseIndex>

pub fn type_var_span(&self, vid: TyVid) -> Span

Returns the span of the type variable identified by vid.

No attempt is made to resolve vid to its root variable.

pub fn const_var_span(&self, vid: ConstVid) -> Option<Span>

Returns the span of the const variable identified by vid

pub fn instantiate_binder_with_fresh_vars<T>( &self, span: Span, _lbrct: BoundRegionConversionTime<'db>, value: Binder<'db, T>, ) -> T

where T: TypeFoldable<DbInterner<'db>> + Clone,

pub fn closure_kind(&self, closure_ty: Ty<'db>) -> Option<ClosureKind>

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 universe(&self) -> UniverseIndex

pub fn create_next_universe(&self) -> UniverseIndex

Creates and return a fresh universe that extends all previous universes. Updates self.universe to that new universe.

pub fn is_ty_infer_var_definitely_unchanged<'a>( &'a self, ) -> impl Fn(TyOrConstInferVar) -> bool + use<'a, 'db>

The returned function is used in a fast path. If it returns true the variable is unchanged, false indicates that the status is unknown.

pub fn ty_or_const_infer_var_changed( &self, infer_var: TyOrConstInferVar, ) -> bool

ty_or_const_infer_var_changed is equivalent to one of these two:

• shallow_resolve(ty) != ty (where ty.kind = Infer(_))
• shallow_resolve(ct) != ct (where ct.kind = 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 Const without having to resort to storing full GenericArgs in stalled_on.

fn sub_unification_table_root_var(&self, var: TyVid) -> TyVid

fn sub_unify_ty_vids_raw(&self, a: TyVid, b: TyVid)

pub fn attach_obligation_inspector(&self, inspector: ObligationInspector<'db>)

Attach a callback to be invoked on each root obligation evaluated in the new trait solver.

pub fn inspect_evaluated_obligation( &self, obligation: &Obligation<'db, Predicate<'db>>, result: &Result<GoalEvaluation<DbInterner<'db>>, NoSolution>, get_proof_tree: impl FnOnce() -> Option<GoalEvaluation<DbInterner<'db>>>, )

impl<'db> InferCtxt<'db>

pub(crate) fn visit_proof_tree<V: ProofTreeVisitor<'db>>( &self, goal: Goal<'db, Predicate<'db>>, visitor: &mut V, ) -> V::Result

pub(crate) fn visit_proof_tree_at_depth<V: ProofTreeVisitor<'db>>( &self, goal: Goal<'db, Predicate<'db>>, depth: usize, visitor: &mut V, ) -> V::Result

Trait Implementations

impl<'db> Clone for InferCtxt<'db>

fn clone(&self) -> InferCtxt<'db>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a, 'db> From<&'a InferCtxt<'db>> for &'a SolverContext<'db>

fn from(infcx: &'a InferCtxt<'db>) -> Self

Converts to this type from the input type.

impl<'db> InferCtxtLike for InferCtxt<'db>

type Interner = DbInterner<'db>

type OpaqueTypeStorageEntries = OpaqueTypeStorageEntries

fn cx(&self) -> DbInterner<'db>

fn next_trait_solver(&self) -> bool

Whether the new trait solver is enabled. This only exists because rustc shares code between the new and old trait solvers; for all other users, this should always be true. If this is unknowingly false and you try to use the new trait solver, things will break badly.

fn disable_trait_solver_fast_paths(&self) -> bool

fn typing_mode_raw(&self) -> TypingMode<DbInterner<'db>>

fn universe(&self) -> UniverseIndex

fn create_next_universe(&self) -> UniverseIndex

fn universe_of_ty(&self, vid: TyVid) -> Option<UniverseIndex>

fn universe_of_lt(&self, lt: RegionVid) -> Option<UniverseIndex>

fn universe_of_ct(&self, ct: ConstVid) -> Option<UniverseIndex>

fn root_ty_var(&self, var: TyVid) -> TyVid

fn root_const_var(&self, var: ConstVid) -> ConstVid

fn opportunistic_resolve_ty_var(&self, vid: TyVid) -> Ty<'db>

fn opportunistic_resolve_int_var(&self, vid: IntVid) -> Ty<'db>

fn opportunistic_resolve_float_var(&self, vid: FloatVid) -> Ty<'db>

fn opportunistic_resolve_ct_var(&self, vid: ConstVid) -> Const<'db>

fn opportunistic_resolve_lt_var(&self, vid: RegionVid) -> Region<'db>

fn is_changed_arg(&self, arg: <Self::Interner as Interner>::GenericArg) -> bool

fn next_ty_infer(&self) -> Ty<'db>

fn next_region_infer(&self) -> <Self::Interner as Interner>::Region

fn next_const_infer(&self) -> Const<'db>

fn fresh_args_for_item(&self, def_id: SolverDefId<'db>) -> GenericArgs<'db>

fn instantiate_binder_with_infer<T: TypeFoldable<DbInterner<'db>> + Clone>( &self, value: Binder<'db, T>, ) -> T

fn enter_forall<T: TypeFoldable<DbInterner<'db>> + Clone, U>( &self, value: Binder<'db, T>, f: impl FnOnce(T) -> U, ) -> U

fn equate_ty_vids_raw(&self, a: TyVid, b: TyVid)

fn equate_int_vids_raw(&self, a: IntVid, b: IntVid)

fn equate_float_vids_raw(&self, a: FloatVid, b: FloatVid)

fn equate_const_vids_raw(&self, a: ConstVid, b: ConstVid)

fn instantiate_ty_var_raw<R: PredicateEmittingRelation<Self>>( &self, relation: &mut R, target_is_expected: bool, target_vid: TyVid, instantiation_variance: Variance, source_ty: Ty<'db>, ) -> RelateResult<'db, ()>

fn instantiate_int_var_raw(&self, vid: IntVid, value: IntVarValue)

fn instantiate_float_var_raw(&self, vid: FloatVid, value: FloatVarValue)

fn instantiate_const_var_raw<R: PredicateEmittingRelation<Self>>( &self, relation: &mut R, target_is_expected: bool, target_vid: ConstVid, source_ct: Const<'db>, ) -> RelateResult<'db, ()>

fn set_tainted_by_errors(&self, e: ErrorGuaranteed)

fn shallow_resolve(&self, ty: Ty<'db>) -> Ty<'db>

fn shallow_resolve_const(&self, ct: Const<'db>) -> Const<'db>

fn resolve_vars_if_possible<T>(&self, value: T) -> T

where T: TypeFoldable<DbInterner<'db>>,

fn probe<T>(&self, probe: impl FnOnce() -> T) -> T

fn sub_regions( &self, sub: Region<'db>, sup: Region<'db>, _vis: VisibleForLeakCheck, _span: Span, )

fn equate_regions( &self, a: Region<'db>, b: Region<'db>, _vis: VisibleForLeakCheck, _span: Span, )

fn register_ty_outlives(&self, _ty: Ty<'db>, _r: Region<'db>, _span: Span)

fn opaque_types_storage_num_entries(&self) -> OpaqueTypeStorageEntries

fn clone_opaque_types_lookup_table(&self) -> Vec<(OpaqueTypeKey<'db>, Ty<'db>)>

fn clone_duplicate_opaque_types(&self) -> Vec<(OpaqueTypeKey<'db>, Ty<'db>)>

fn clone_opaque_types_added_since( &self, prev_entries: OpaqueTypeStorageEntries, ) -> Vec<(OpaqueTypeKey<'db>, Ty<'db>)>

fn register_hidden_type_in_storage( &self, opaque_type_key: OpaqueTypeKey<'db>, hidden_ty: Ty<'db>, _span: Span, ) -> Option<Ty<'db>>

fn add_duplicate_opaque_type( &self, opaque_type_key: OpaqueTypeKey<'db>, hidden_ty: Ty<'db>, _span: Span, )

fn reset_opaque_types(&self)

fn sub_unification_table_root_var(&self, var: TyVid) -> TyVid

fn sub_unify_ty_vids_raw(&self, a: TyVid, b: TyVid)

fn opaques_with_sub_unified_hidden_type( &self, _ty: TyVid, ) -> Vec<AliasTy<Self::Interner>>

impl<'db> PredicateEmittingRelation<InferCtxt<'db>> for LatticeOp<'_, 'db>

fn span(&self) -> Span

fn structurally_relate_aliases(&self) -> StructurallyRelateAliases

Whether aliases should be related structurally. This is pretty much always No unless you’re equating in some specific locations of the new solver. See the comments in these use-cases for more details.

fn param_env(&self) -> ParamEnv<'db>

fn register_predicates( &mut self, preds: impl IntoIterator<Item: Upcast<DbInterner<'db>, Predicate<'db>>>, )

Register predicates that must hold in order for this relation to hold. This uses the default param_env of the obligation.

fn register_goals( &mut self, goals: impl IntoIterator<Item = Goal<'db, Predicate<'db>>>, )

Register obligations that must hold in order for this relation to hold

fn register_alias_relate_predicate(&mut self, a: Ty<'db>, b: Ty<'db>)

Register AliasRelate obligation(s) that both types must be related to each other.