Function renumber_bindings

src/transform/src/normalize_lets.rs:950–958

Re-assign an identifier to each `Let`. Under the assumption that `id_gen` produces identifiers in order, this process maintains in-orderness of `LetRec` identifiers.

(
        relation: &mut MirRelationExpr,
        id_gen: &mut IdGen,
    )

    /// Under the assumption that `id_gen` produces identifiers in order, this process
    /// maintains in-orderness of `LetRec` identifiers.
    pub fn renumber_bindings(
        relation: &mut MirRelationExpr,
        id_gen: &mut IdGen,
    ) -> Result<(), crate::TransformError> {
        let mut renaming = BTreeMap::new();
        determine(&*relation, &mut renaming, id_gen)?;
        implement(relation, &renaming)?;
        Ok(())
    }

    /// Performs an in-order traversal of the AST, assigning identifiers as it goes.
    fn determine(