Class Identifier

datafusion/common/src/cse.rs:79–85

/// "have no collision (as low as possible)"
#[derive(Debug, Eq)]
struct Identifier<'n, N: NormalizeEq> {
    // Hash of `node` built up incrementally during the first, visiting traversal.
    // Its value is not necessarily equal to default hash of the node. E.g. it is not
    // equal to `expr.hash()` if the node is `Expr`.
    hash: u64,
    node: &'n N,
}

impl<N: NormalizeEq> Clone for Identifier<'_, N> {
    fn clone(&self) -> Self {