Module rustc_trait_selection::traits::solve::inspect

Data structure used to inspect trait solver behavior.

During trait solving we optionally build “proof trees”, the root of which is a GoalEvaluation with GoalEvaluationKind::Root. These trees are used to improve the debug experience and are also used by the compiler itself to provide necessary context for error messages.

Because each nested goal in the solver gets canonicalized separately and we discard inference progress via “probes”, we cannot mechanically use proof trees without somehow “lifting up” data local to the current InferCtxt. Any data used mechanically is therefore canonicalized and stored as CanonicalState. As printing canonicalized data worsens the debugging dumps, we do not simply canonicalize everything.

This means proof trees contain inference variables and placeholders local to a different InferCtxt which must not be used with the current one.

Structs

• AddedGoalsEvaluation
• CanonicalGoalEvaluation
• GoalEvaluation
• GoalEvaluationStep
• Probe
  A self-contained computation during trait solving. This either corresponds to a EvalCtxt::probe(_X) call or the root evaluation of a goal.
• State
  Some data together with information about how they relate to the input of the canonical query.

Enums

• CacheHit
• CanonicalGoalEvaluationKind
• GoalEvaluationKind
  When evaluating the root goals we also store the original values for the CanonicalVarValues of the canonicalized goal. We use this to map any CanonicalState from the local InferCtxt of the solver query to the InferCtxt of the caller.
• ProbeKind
  What kind of probe we’re in. In case the probe represents a candidate, or the final result of the current goal - via ProbeKind::Root - we also store the QueryResult.
• ProbeStep

Type Aliases

• CanonicalState