index: move lifetimed change_id_index() to MutableIndex, rename 'static version

change_id_index() is only used by Readonly/MutableRepo, so we don't need an
abstraction at Index. evaluate_revset() is somewhat similar, but the callers
rely on &dyn Repo.

lib/src/default_index/composite.rs

@@ -296,13 +296,6 @@ impl<'a> CompositeIndex<'a> {
         candidate_positions
     }
 
-    pub(super) fn change_id_index(
-        &self,
-        heads: &mut dyn Iterator<Item = &CommitId>,
-    ) -> Box<dyn ChangeIdIndex + 'a> {
-        Box::new(ChangeIdIndexImpl::new(*self, heads))
-    }
-
     pub(super) fn evaluate_revset(
         &self,
         expression: &ResolvedExpression,
@@ -389,13 +382,6 @@ impl Index for CompositeIndex<'_> {
         ids
     }
 
-    fn change_id_index(
-        &self,
-        heads: &mut dyn Iterator<Item = &CommitId>,
-    ) -> Box<dyn ChangeIdIndex + '_> {
-        CompositeIndex::change_id_index(self, heads)
-    }
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,

lib/src/default_index/mutable.rs

@@ -29,7 +29,7 @@ use itertools::Itertools;
 use smallvec::SmallVec;
 use tempfile::NamedTempFile;
 
-use super::composite::{AsCompositeIndex, CompositeIndex, IndexSegment};
+use super::composite::{AsCompositeIndex, ChangeIdIndexImpl, CompositeIndex, IndexSegment};
 use super::entry::{IndexPosition, LocalPosition, SmallIndexPositionsVec};
 use super::readonly::{DefaultReadonlyIndex, ReadonlyIndexSegment};
 use crate::backend::{ChangeId, CommitId};
@@ -442,13 +442,6 @@ impl Index for DefaultMutableIndex {
         self.as_composite().topo_order(input)
     }
 
-    fn change_id_index(
-        &self,
-        heads: &mut dyn Iterator<Item = &CommitId>,
-    ) -> Box<dyn ChangeIdIndex + '_> {
-        self.as_composite().change_id_index(heads)
-    }
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,
@@ -471,6 +464,13 @@ impl MutableIndex for DefaultMutableIndex {
         self
     }
 
+    fn change_id_index(
+        &self,
+        heads: &mut dyn Iterator<Item = &CommitId>,
+    ) -> Box<dyn ChangeIdIndex + '_> {
+        Box::new(ChangeIdIndexImpl::new(self, heads))
+    }
+
     fn add_commit(&mut self, commit: &Commit) {
         self.0.add_commit(commit);
     }

lib/src/default_index/readonly.rs

@@ -509,14 +509,6 @@ impl Index for DefaultReadonlyIndex {
         self.as_composite().topo_order(input)
     }
 
-    // TODO: Create a persistent lookup from change id to commit ids.
-    fn change_id_index(
-        &self,
-        heads: &mut dyn Iterator<Item = &CommitId>,
-    ) -> Box<dyn ChangeIdIndex + '_> {
-        self.as_composite().change_id_index(heads)
-    }
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,
@@ -535,7 +527,8 @@ impl ReadonlyIndex for DefaultReadonlyIndex {
         self
     }
 
-    fn change_id_index_static(
+    // TODO: Create a persistent lookup from change id to commit ids.
+    fn change_id_index(
         &self,
         heads: &mut dyn Iterator<Item = &CommitId>,
     ) -> Box<dyn ChangeIdIndex> {

lib/src/index.rs

@@ -72,11 +72,6 @@ pub trait Index: Send + Sync {
     /// Parents before children
     fn topo_order(&self, input: &mut dyn Iterator<Item = &CommitId>) -> Vec<CommitId>;
 
-    fn change_id_index(
-        &self,
-        heads: &mut dyn Iterator<Item = &CommitId>,
-    ) -> Box<dyn ChangeIdIndex + '_>;
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,
@@ -89,12 +84,8 @@ pub trait ReadonlyIndex: Send + Sync {
 
     fn as_index(&self) -> &dyn Index;
 
-    // TODO: might be better to split Index::change_id_index() to
-    // Readonly/MutableIndex::change_id_index_static().
-    fn change_id_index_static(
-        &self,
-        heads: &mut dyn Iterator<Item = &CommitId>,
-    ) -> Box<dyn ChangeIdIndex>;
+    fn change_id_index(&self, heads: &mut dyn Iterator<Item = &CommitId>)
+        -> Box<dyn ChangeIdIndex>;
 
     fn start_modification(&self) -> Box<dyn MutableIndex>;
 }
@@ -106,6 +97,11 @@ pub trait MutableIndex {
 
     fn as_index(&self) -> &dyn Index;
 
+    fn change_id_index(
+        &self,
+        heads: &mut dyn Iterator<Item = &CommitId>,
+    ) -> Box<dyn ChangeIdIndex + '_>;
+
     fn add_commit(&mut self, commit: &Commit);
 
     fn merge_in(&mut self, other: &dyn ReadonlyIndex);

lib/src/repo.rs

@@ -265,10 +265,8 @@ impl ReadonlyRepo {
     fn change_id_index(&self) -> &dyn ChangeIdIndex {
         self.change_id_index
             .get_or_init(|| {
-                // TODO: maybe add abstraction over 'static/'index revset
-                // evaluation, and use it.
                 self.readonly_index()
-                    .change_id_index_static(&mut self.view().heads().iter())
+                    .change_id_index(&mut self.view().heads().iter())
             })
             .as_ref()
     }
@@ -1401,16 +1399,12 @@ impl Repo for MutableRepo {
     }
 
     fn resolve_change_id_prefix(&self, prefix: &HexPrefix) -> PrefixResolution<Vec<CommitId>> {
-        let change_id_index = self
-            .index()
-            .change_id_index(&mut self.view().heads().iter());
+        let change_id_index = self.index.change_id_index(&mut self.view().heads().iter());
         change_id_index.resolve_prefix(prefix)
     }
 
     fn shortest_unique_change_id_prefix_len(&self, target_id: &ChangeId) -> usize {
-        let change_id_index = self
-            .index()
-            .change_id_index(&mut self.view().heads().iter());
+        let change_id_index = self.index.change_id_index(&mut self.view().heads().iter());
         change_id_index.shortest_unique_prefix_len(target_id)
     }
 }

lib/tests/test_index.rs

@@ -674,7 +674,7 @@ fn test_change_id_index() {
 
     let index_for_heads = |commits: &[&Commit]| {
         tx.repo()
-            .index()
+            .mutable_index()
             .change_id_index(&mut commits.iter().map(|commit| commit.id()))
     };
     let change_id_index = index_for_heads(&[&commit_1, &commit_2, &commit_3, &commit_4, &commit_5]);