Module rustc_infer::traits[][src]

Expand description

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


pub use self::FulfillmentErrorCode::*;
pub use self::ImplSource::*;
pub use self::ObligationCauseCode::*;
pub use self::SelectionError::*;


Code for projecting associated types out of trait references.

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.

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


A chalk environment and goal.

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

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).

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

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.


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

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

Reasons a method might not be object-safe.

Indicates that trait evaluation caused overflow and in which pass.

Depending on the stage of compilation, we want projection to be more or less conservative.

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>).


Type Definitions

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