+use crate::definitions::{DefKey, DefPathData, DisambiguatedDefPathData};
+use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_span::crate_disambiguator::CrateDisambiguator;
+use rustc_span::def_id::{DefPathHash, StableCrateId};
+
+#[test]
+fn def_path_hash_depends_on_crate_id() {
+ // This test makes sure that *both* halves of a DefPathHash depend on
+ // the crate-id of the defining crate. This is a desirable property
+ // because the crate-id can be more easily changed than the DefPath
+ // of an item, so, in the case of a crate-local DefPathHash collision,
+ // the user can simply "role the dice again" for all DefPathHashes in
+ // the crate by changing the crate disambiguator (e.g. via bumping the
+ // crate's version number).
+
+ let d0 = CrateDisambiguator::from(Fingerprint::new(12, 34));
+ let d1 = CrateDisambiguator::from(Fingerprint::new(56, 78));
+
+ let h0 = mk_test_hash("foo", d0);
+ let h1 = mk_test_hash("foo", d1);
+
+ assert_ne!(h0.stable_crate_id(), h1.stable_crate_id());
+ assert_ne!(h0.local_hash(), h1.local_hash());
+
+ fn mk_test_hash(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> DefPathHash {
+ let stable_crate_id = StableCrateId::new(crate_name, crate_disambiguator);
+ let parent_hash = DefPathHash::new(stable_crate_id, 0);
+
+ let key = DefKey {
+ parent: None,
+ disambiguated_data: DisambiguatedDefPathData {
+ data: DefPathData::CrateRoot,
+ disambiguator: 0,
+ },
+ };
+
+ key.compute_stable_hash(parent_hash)
+ }
+}