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args_known_to_outlive_opaque_params

rustc_trait_selection::traits::outlives_for_liveness

Function args_known_to_outlive_opaque_params 

Source 
pub(crate) fn args_known_to_outlive_opaque_params<'tcx>(
    tcx: TyCtxt<'tcx>,
    def_id: LocalDefId,
) -> EarlyBinder<'tcx, Vec<(Region<'tcx>, Vec<GenericArg<'tcx>>)>>
Expand description

For each captured region of this alias, compute the captured identity args that are known to outlive it, given the definition of the opaque type in the the parent context.

Some examples:

ⓘ
// Returns `[('a, ['a]), ('b, ['b])]`
fn foo<'a, 'b>() -> impl Sized + use<'a, 'b> {}

// Returns `[('a, ['a]), ('b, ['b])]`
fn foo<'a: 'a, 'b>() -> impl Sized + use<'a, 'b> {}

// Returns `[('a, ['a])]`
fn foo<'a, 'b>() -> impl Sized + use<'a> {}

// Returns `[('a, ['a, 'b]), ('b, ['b])]`
fn foo<'a, 'b: 'a>() -> impl Sized + use<'a, 'b> {}

// Returns `[('a, ['a, 'b]), ('b, ['b])]`
fn foo<'a, 'b>(_: &'a &'b ()) -> impl Sized + use<'a, 'b> {}

Importantly:

  • All captured regions are considered (not just those in outlives bounds)
  • It doesn’t matter if the captured region is early-bound or late-bound