Function id_gen

src/expr/src/explain.rs:283–294

Create an [`Iterator`] for [`LocalId`] values that are guaranteed to be fresh within the scope of the given [`MirRelationExpr`].

(expr: &MirRelationExpr)

// Create an [`Iterator`] for [`LocalId`] values that are guaranteed to be
// fresh within the scope of the given [`MirRelationExpr`].
fn id_gen(expr: &MirRelationExpr) -> impl Iterator<Item = LocalId> + use<> {
    let mut max_id = 0_u64;

    expr.visit_pre(|expr| {
        match expr {
            MirRelationExpr::Let { id, .. } => max_id = std::cmp::max(max_id, id.into()),
            _ => (),
        };
    });

    (max_id + 1..).map(LocalId::new)
}

impl ScalarOps for MirScalarExpr {
    fn match_col_ref(&self) -> Option<usize> {