Enum Binding 

pub enum Binding {
    Leaf(Expr),
    Group(Rc<GroupPlan>),
    Inherit,
    InheritFrom {
        from: usize,
    },
}

A binding after normalization.

Variants

Leaf(Expr)

A value that is NOT a syntactic attrset literal, so it can never merge.

Group(Rc<GroupPlan>)

A syntactic attrset literal, or an implicit one created by a dotted path. Mergeable — and merging splices into THIS node.

Rc because a consumer clones a sub-plan every time it builds the nested group lazily; owned, that is a DEEP copy of the whole subtree on each evaluation. During construction the Rc is uniquely owned, so Rc::make_mut below is a no-op rather than a copy.

Inherit

inherit x — resolve x in the group’s ENCLOSING scope, never its own rec scope. That is what makes an inherited binding shadow rather than self-reference, and why it can never merge.

InheritFrom

inherit (e) x — force GroupPlan::inherit_froms[from], then select.

★ An INDEX, not a cloned expression. One inherit (e) a b c; clause must evaluate e AT MOST ONCE and share the result across all three names; cloning the expr per name evaluates it three times, which is observable through builtins.trace and through any impure source. The index is per-GROUP because the splice moves a clause between groups.

Fields

from: usize

Index into the owning GroupPlan::inherit_froms.

Trait Implementations

impl Clone for Binding

fn clone(&self) -> Binding

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Binding

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.