Function rustc_trait_selection::traits::outlives_bounds::implied_outlives_bounds

fn implied_outlives_bounds<'a, 'tcx>(
    infcx: &'a InferCtxt<'tcx>,
    param_env: ParamEnv<'tcx>,
    body_id: LocalDefId,
    ty: Ty<'tcx>,
    compat: bool
) -> Vec<OutlivesBound<'tcx>>

Implied bounds are region relationships that we deduce automatically. The idea is that (e.g.) a caller must check that a function’s argument types are well-formed immediately before calling that fn, and hence the callee can assume that its argument types are well-formed. This may imply certain relationships between generic parameters. For example:

fn foo<T>(x: &T) {}

can only be called with a 'a and T such that &'a T is WF. For &'a T to be WF, T: 'a must hold. So we can assume T: 'a.

Parameters

• param_env, the where-clauses in scope
• body_id, the body-id to use when normalizing assoc types. Note that this may cause outlives obligations to be injected into the inference context with this body-id.
• ty, the type that we are supposed to assume is WF.