Struct rustc_trait_selection::traits::specialization_graph::Graph

pub struct Graph {
    pub parent: HashMap<DefId, DefId, BuildHasherDefault<FxHasher>>,
    pub children: HashMap<DefId, Children, BuildHasherDefault<FxHasher>>,
    pub has_errored: bool,
}

A per-trait graph of impls in specialization order. At the moment, this graph forms a tree rooted with the trait itself, with all other nodes representing impls, and parent-child relationships representing specializations.

The graph provides two key services:

• Construction. This implicitly checks for overlapping impls (i.e., impls that overlap but where neither specializes the other – an artifact of the simple “chain” rule.

• Parent extraction. In particular, the graph can give you the immediate parents of a given specializing impl, which is needed for extracting default items amongst other things. In the simple “chain” rule, every impl has at most one parent.

Fields

parent: HashMap<DefId, DefId, BuildHasherDefault<FxHasher>>

All impls have a parent; the “root” impls have as their parent the def_id of the trait.

children: HashMap<DefId, Children, BuildHasherDefault<FxHasher>>

The “root” impls are found by looking up the trait’s def_id.

has_errored: bool

Whether an error was emitted while constructing the graph.

Trait Implementations

impl GraphExt for Graph

fn insert<'tcx>(
    &mut self,
    tcx: TyCtxt<'tcx>,
    impl_def_id: DefId
) -> Result<Option<FutureCompatOverlapError>, OverlapError>

Insert a local impl into the specialization graph. If an existing impl conflicts with it (has overlap, but neither specializes the other), information about the area of overlap is returned in the Err.

fn record_impl_from_cstore<'tcx>(
    &mut self,
    tcx: TyCtxt<'tcx>,
    parent: DefId,
    child: DefId
)

Insert cached metadata mapping from a child impl back to its parent.