Struct rustc_trait_selection::infer::InferCtxtBuilder

pub struct InferCtxtBuilder<'tcx> {
    tcx: TyCtxt<'tcx>,
    fresh_typeck_results: Option<RefCell<TypeckResults<'tcx>>>,
}

Helper type of a temporary returned by tcx.infer_ctxt(). Necessary because we can't write the following bound: F: for<'b, 'tcx> where 'tcx FnOnce(InferCtxt<'b, 'tcx>).

Fields

tcx: TyCtxt<'tcx>

fresh_typeck_results: Option<RefCell<TypeckResults<'tcx>>>

Implementations

impl<'tcx> InferCtxtBuilder<'tcx>

pub fn with_fresh_in_progress_typeck_results(
    self,
    table_owner: LocalDefId
) -> InferCtxtBuilder<'tcx>

Used only by rustc_typeck during body type-checking/inference, will initialize in_progress_typeck_results with fresh TypeckResults.

pub fn enter_with_canonical<T, R>(
    &mut self,
    span: Span,
    canonical: &Canonical<'tcx, T>,
    f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R
) -> R where
    T: TypeFoldable<'tcx>, 

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 substitution S. This substitution S maps from the bound values in C to their instantiated values in V (in other words, S(C) = V).

pub fn enter<R>(
    &mut self,
    f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R
) -> R

Trait Implementations

impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx>

fn enter_canonical_trait_query<K, R>(
    &mut self,
    canonical_key: &Canonical<'tcx, K>,
    operation: impl FnOnce(&InferCtxt<'_, 'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>
) -> Fallible<CanonicalizedQueryResponse<'tcx, R>> where
    K: TypeFoldable<'tcx>,
    R: Debug + TypeFoldable<'tcx>,
    Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>, 

The "main method" for a canonicalized trait query. Given the canonical key canonical_key, this method will create a new inference context, instantiate the key, and run your operation op. The operation should yield up a result (of type R) as well as a set of trait obligations that must be fully satisfied. These obligations will be processed and the canonical result created.

Returns NoSolution in the event of any error.

(It might be mildly nicer to implement this on TyCtxt, and not InferCtxtBuilder, but that is a bit tricky right now. In part because we would need a for<'tcx> sort of bound for the closure and in part because it is convenient to have 'tcx be free on this function so that we can talk about K: TypeFoldable<'tcx>.)