diff rust/hg-core/src/dagops.rs @ 50979:4c5f6e95df84

rust: make `Revision` a newtype

This change is the one we've been building towards during this series.
The aim is to make `Revision` mean more than a simple integer, holding
the information that it is valid for a given revlog index.
While this still allows for programmer error, since creating a revision
directly and querying a different index with a "checked" revision are
still possible, the friction created by the newtype will hopefully make
us think twice about which type to use.

Enough of the Rust ecosystem relies on the newtype pattern to be
efficiently optimized away (even compiler in codegen tests¹), so I'm not
worried about this being a fundamental problem.

[1] https://github.com/rust-lang/rust/blob/7a70647f195f6b0a0f1ebd72b1542ba91a32f43a/tests/codegen/vec-in-place.rs#L47

--- a/rust/hg-core/src/dagops.rs	Thu Aug 10 11:01:07 2023 +0200
+++ b/rust/hg-core/src/dagops.rs	Fri Aug 18 14:34:29 2023 +0200
@@ -171,14 +171,15 @@
 mod tests {
 
     use super::*;
-    use crate::testing::SampleGraph;
+    use crate::{testing::SampleGraph, BaseRevision};
 
     /// Apply `retain_heads()` to the given slice and return as a sorted `Vec`
     fn retain_heads_sorted(
         graph: &impl Graph,
-        revs: &[Revision],
+        revs: &[BaseRevision],
     ) -> Result<Vec<Revision>, GraphError> {
-        let mut revs: HashSet<Revision> = revs.iter().cloned().collect();
+        let mut revs: HashSet<Revision> =
+            revs.iter().cloned().map(Revision).collect();
         retain_heads(graph, &mut revs)?;
         let mut as_vec: Vec<Revision> = revs.iter().cloned().collect();
         as_vec.sort_unstable();
@@ -202,9 +203,11 @@
     /// Apply `heads()` to the given slice and return as a sorted `Vec`
     fn heads_sorted(
         graph: &impl Graph,
-        revs: &[Revision],
+        revs: &[BaseRevision],
     ) -> Result<Vec<Revision>, GraphError> {
-        let heads = heads(graph, revs.iter())?;
+        let iter_revs: Vec<_> =
+            revs.into_iter().cloned().map(Revision).collect();
+        let heads = heads(graph, iter_revs.iter())?;
         let mut as_vec: Vec<Revision> = heads.iter().cloned().collect();
         as_vec.sort_unstable();
         Ok(as_vec)
@@ -227,9 +230,9 @@
     /// Apply `roots()` and sort the result for easier comparison
     fn roots_sorted(
         graph: &impl Graph,
-        revs: &[Revision],
+        revs: &[BaseRevision],
     ) -> Result<Vec<Revision>, GraphError> {
-        let set: HashSet<_> = revs.iter().cloned().collect();
+        let set: HashSet<_> = revs.iter().cloned().map(Revision).collect();
         let mut as_vec = roots(graph, &set)?;
         as_vec.sort_unstable();
         Ok(as_vec)
@@ -252,17 +255,24 @@
     /// Apply `range()` and convert the result into a Vec for easier comparison
     fn range_vec(
         graph: impl Graph + Clone,
-        roots: &[Revision],
-        heads: &[Revision],
+        roots: &[BaseRevision],
+        heads: &[BaseRevision],
     ) -> Result<Vec<Revision>, GraphError> {
-        range(&graph, roots.iter().cloned(), heads.iter().cloned())
-            .map(|bs| bs.into_iter().collect())
+        range(
+            &graph,
+            roots.iter().cloned().map(Revision),
+            heads.iter().cloned().map(Revision),
+        )
+        .map(|bs| bs.into_iter().collect())
     }
 
     #[test]
     fn test_range() -> Result<(), GraphError> {
         assert_eq!(range_vec(SampleGraph, &[0], &[4])?, vec![0, 1, 2, 4]);
-        assert_eq!(range_vec(SampleGraph, &[0], &[8])?, vec![]);
+        assert_eq!(
+            range_vec(SampleGraph, &[0], &[8])?,
+            Vec::<Revision>::new()
+        );
         assert_eq!(
             range_vec(SampleGraph, &[5, 6], &[10, 11, 13])?,
             vec![5, 10]