Module traits

Trait Resolution. See the rustc-dev-guide for more information on how this works.

Re-exports

pub use self::ImplSource::*;

pub use self::SelectionError::*;

Modules

engine 🔒

project 🔒

Code for projecting associated types out of trait references.

query

Experimental types for the trait query interface. The methods defined in this module are all based on canonicalization, which makes a canonical query by replacing unbound inference variables and regions, so that results can be reused more broadly. The providers for the queries defined here can be found in rustc_traits.

select

Candidate selection. See the rustc dev guide for more information on how this works.

solve

specialization_graph

structural_impls 🔒

util

Structs

DerivedCause

DerivedHostCause

IfExpressionCause

ImplDerivedCause

ImplDerivedHostCause

ImplSourceUserDefinedData

Identifies a particular impl in the source, along with a set of generic parameters from the impl’s type/lifetime parameters. The nested vector corresponds to the nested obligations attached to the impl’s type parameters.

MatchExpressionArmCause

MismatchedProjectionTypes

Normalized

Obligation

An Obligation represents some trait reference (e.g., i32: Eq) for which the “impl_source” must be found. The process of finding an “impl_source” is called “resolving” the Obligation. This process consists of either identifying an impl (e.g., impl Eq for i32) that satisfies the obligation, or else finding a bound that is in scope. The eventual result is usually a Selection (defined below).

ObligationCause

The reason why we incurred this obligation; used for error reporting.

ObligationCauseCodeHandle

A compact form of ObligationCauseCode.

PatternOriginExpr

Information about the origin expression of a pattern, relevant to diagnostics. Fields here refer to the scrutinee of a pattern. If the scrutinee isn’t given in the diagnostic, then this won’t exist.

ProjectionCache

The projection cache. Unlike the standard caches, this can include infcx-dependent type variables, therefore we have to roll the cache back each time we roll a snapshot back, to avoid assumptions on yet-unresolved inference variables. Types with placeholder regions also have to be removed when the respective snapshot ends.

ProjectionCacheKey

ProjectionCacheStorage

SignatureMismatchData

Enums

BuiltinImplSource

CodegenObligationError

These are the error cases for codegen_select_candidate.

DynCompatibilityViolation

DynCompatibilityViolationSolution

EvaluationResult

The result of trait evaluation. The order is important here as the evaluation of a list is the maximum of the evaluations.

ImplSource

Given the successful resolution of an obligation, the ImplSource indicates where the impl comes from.

IsConstable

Whether a value can be extracted into a const. Used for diagnostics around array repeat expressions.

MethodViolationCode

Reasons a method might not be dyn-compatible.

ObligationCauseCode

OverflowError

Indicates that trait evaluation caused overflow and in which pass.

ProjectionCacheEntry

ScrubbedTraitError

A trait error with most of its information removed. This is the error returned by an ObligationCtxt by default, and suitable if you just want to see if a predicate holds, and don’t particularly care about the error itself (except for if it’s an ambiguity or true error).

SelectionError

WellFormedLoc

The ‘location’ at which we try to perform HIR-based wf checking. This information is used to obtain an hir::Ty, which we can walk in order to obtain precise spans for any ‘nested’ types (e.g. Foo in Option<Foo>).

Traits

FromSolverError

TraitEngine

Type Aliases

EvaluationCache

NormalizedTerm

ObligationInspector

A callback that can be provided to inspect_typeck. Invoked on evaluation of root obligations.

PolyTraitObligation

PredicateObligation

PredicateObligations

Selection

SelectionCache

SelectionResult

When performing resolution, it is typically the case that there can be one of three outcomes:

TraitObligation