Enum rustc_trait_selection::infer::region_constraints::Constraint

pub enum Constraint<'tcx> {
    VarSubVar(RegionVid, RegionVid),
    RegSubVar(&'tcx RegionKind, RegionVid),
    VarSubReg(RegionVid, &'tcx RegionKind),
    RegSubReg(&'tcx RegionKind, &'tcx RegionKind),
}

Represents a constraint that influences the inference process.

Variants

VarSubVar(RegionVid, RegionVid)

A region variable is a subregion of another.

RegSubVar(&'tcx RegionKind, RegionVid)

A concrete region is a subregion of region variable.

VarSubReg(RegionVid, &'tcx RegionKind)

A region variable is a subregion of a concrete region. This does not directly affect inference, but instead is checked after inference is complete.

RegSubReg(&'tcx RegionKind, &'tcx RegionKind)

A constraint where neither side is a variable. This does not directly affect inference, but instead is checked after inference is complete.