Module infer

Modules

• at
  A nice interface for working with the infcx. The basic idea is to do infcx.at(cause, param_env), which sets the “cause” of the operation as well as the surrounding parameter environment. Then you can do something like .sub(a, b) or .eq(a, b) to create a subtype or equality relationship respectively. The first argument is always the “expected” output from the POV of diagnostics.
• canonical
  Canonicalization is the key to constructing a query in the middle of type inference. Ordinarily, it is not possible to store types from type inference in query keys, because they contain references to inference variables whose lifetimes are too short and so forth. Canonicalizing a value T1 using canonicalize_query produces two things:
• outlives
  Various code related to computing outlives relations.
• region_constraints
  See README.md.
• relate
  This module contains the definitions of most TypeRelations in the type system (except for some relations used for diagnostics and heuristics in the compiler). As well as the implementation of Relate for interned things (Ty/Const/etc).
• resolve

Structs

• FixupError
• InferCtxt
• InferCtxtBuilder
  Used to configure inference contexts before their creation.
• InferCtxtInner
  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.
• InferOk
  InferOk<'tcx, ()> is used a lot. It may seem like a useless wrapper around PredicateObligations<'tcx>, but it has one important property: because InferOk is marked with #[must_use], if you have a method InferCtxt::f that returns InferResult<'tcx, ()> and you call it with infcx.f()?; you’ll get a warning about the obligations being discarded without use, which is probably unintentional and has been a source of bugs in the past.
• RegionObligation
  See the region_obligations field for more information.
• TypeFreshener
• TypeTrace
  The trace designates the path through inference that we took to encounter an error or subtyping constraint.

Enums

• BoundRegionConversionTime
  Times when we replace bound regions with existentials:
• DefineOpaqueTypes
  Whether we should define opaque types or just treat them opaquely.
• IntVarValue
• NllRegionVariableOrigin
• RegionResolutionError
• RegionVariableOrigin
  Reasons to create a region inference variable.
• StructurallyRelateAliases
  Whether aliases should be related structurally or not. Used to adjust the behavior of generalization and combine.
• SubregionOrigin
  The origin of a r1 <= r2 constraint.
• TyOrConstInferVar
  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.
• ValuePairs
  See the error_reporting module for more details.

Traits

• InferCtxtBuilderExt
• InferCtxtExt
• PredicateEmittingRelation
• TyCtxtInferExt

Type Aliases

• InferResult

Derive Macros

• TypeFoldable
  Derives TypeFoldable for the annotated struct or enum (union is not supported).
• TypeVisitable
  Derives TypeVisitable for the annotated struct or enum (union is not supported).