Module region_constraint 

The bulk of the logic for implementing -Zassumptions-on-binders

Structs

And

An AND of leaf constraints. Always in “canonical form”, meaning:

Assumptions

HigherRankedAliasMatcher 🔒

Or

An OR of AND of LEAF constraints. Always in “canonical form” meaning:

PlaceholderReplacer

RegionConstraint

An And and an Or constraint both in canonical forms, with two additional constraints:

Enums

LeafRegionConstraint

Functions

alias_outlives_candidates_from_assumptions 🔒

Converts an AliasTyOutlivesViaEnv constraint into an OR of region outlives constraints by matching the alias against any Alias: 'a assumptions. This is somewhat tricky as we have a potentially higher ranked alias being equated with a potentially higher ranked assumption and we don’t handle it correctly right now (though it is a somewhat reasonable halfway step).

compute_new_region_constraints 🔒

Filter our region constraints to not include constraints between region variables from u and other regions as those are always satisfied. This requires some care to handle correctly for example: '!a_u1: '?x_u1: '!b_u1 should result in us requiring '!a_u1: '!b_u1 rather than dropping the two constraints entirely.

destructure_type_outlives_constraints_in_root

Converts type outlives constraints into region outlives constraints. This assumes the complete set of assumptions are known. This should not be called until the end of type checking.

eagerly_handle_placeholders_in_universe

Takes any constraints involving placeholders from the current universe and eagerly checks them. This can be done a few ways:

propagate_ambiguity

Force the whole constraint to be ambiguous if it contains ambiguities which could have caused the constraint to be false if they had been false themselves.

pull_region_outlives_constraints_out_of_universe 🔒

Handles converting region outlives constraints involving placeholders from u into OR constraints involving regions from smaller universes with known relationships to the placeholder. For example:

regions_outlived_by

Returns all regions r2 for which r: r2 is known to hold in the universe associated with assumptions

regions_outlived_by_placeholder

Returns all regions r for which !t: r is known to hold in the universe associated with assumptions

regions_outliving

Returns all regions r2 for which r2: r is known to hold in the universe associated with assumptions

rewrite_alias_ty_outlives_constraints_in_universe_for_eager_placeholder_handling 🔒

rewrite_placeholder_ty_outlives_constraints_in_universe_for_eager_placeholder_handling 🔒

rewrite_type_outlives_constraints_in_universe_for_eager_placeholder_handling 🔒

Converts type outlives constraints into either region outlives constraints, or type outlives constraints which do not contain anything from u.