Enum VariableReference 

pub enum VariableReference {
    Scope {
        frame_id: i32,
        kind: ScopeKind,
    },
    EvalResult {
        counter: i32,
    },
    Child {
        parent: i32,
        index: u32,
    },
}

A typed, codec-backed reference into the DAP variablesReference wire space.

Wire ranges (pairwise disjoint)

• Scope: [1, 999_999] — frame_id * 10 + kind (frame_id ∈ [0, 99_999], kind ∈ [1,3])
• EvalResult: [1_000_000, 1_999_999_999] — 1_000_000 + counter
• Child: [2_000_000_000, i32::MAX] — 2_000_000_000 + (parent << 16 | index)

Wire value 0 is reserved/invalid (DAP: 0 = “no children”). Negative values are invalid. Values in [1_000_000..2_000_000_000) not matching any band decode to None.

Encode contract

encode() returns None when encoding would bleed a wire value into another variant’s band:

• Scope: None when frame_id > 99_999 (would overflow into the EvalResult band).
• EvalResult: None when 1_000_000 + counter > EVAL_MAX (counter ≥ 1_999_000_000, practically unreachable, but enforced for type-level correctness).
• Child: None when parent < 0 (negative parent produces wire in the EvalResult band, violating the disjoint-band invariant; saturating arithmetic for non-negative inputs).

All fields are primitive scalar types, so VariableReference is Copy.

Variants

Scope

A scope reference: variables in kind scope at stack frame frame_id.

Valid range: frame_id ∈ [0, 99_999].

Fields

frame_id: i32

Stack frame identifier (0-based; must be ≤ 99_999 for a valid wire encoding).

kind: ScopeKind

Which scope within the frame.

EvalResult

A structured evaluation result reference (HASH or ARRAY from evaluate).

Fields

counter: i32

Monotonically increasing counter allocated per evaluation result.

Child

A child variable reference within a parent variable.

Fields

parent: i32

The parent variable reference (the Scope or EvalResult that owns this child).

Must be a non-negative, previously encoded variablesReference (always ≥ 0 by the DAP spec). Negative values are invalid and encode() returns None.

index: u32

Zero-based index of the child within the parent’s variable list.

Implementations

impl VariableReference

pub fn encode(&self) -> Option<i32>

Encode this reference to an i32 wire value.

Returns None when encoding would produce a wire value outside the variant’s band:

• Scope: None when frame_id is out of [0, 99_999] (would bleed into EvalResult band).
• EvalResult: None when counter is negative or 1_000_000 + counter > 1_999_999_999 (would bleed into Child band; requires counter ≥ 1_999_000_000, practically unreachable).
• Child: None when parent < 0 (negative parent is semantically invalid — a DAP variablesReference is always non-negative, and negative parents produce wire values in the EvalResult band, corrupting the disjoint-band invariant).

pub fn decode(raw: i32) -> Option<Self>

Decode a wire i32 value into a VariableReference.

Uses pure-range classification against the three disjoint bands:

• raw in [2_000_000_000, i32::MAX] → Child
• raw in [1_000_000, 1_999_999_999] → EvalResult{counter: raw - 1_000_000}
• raw in [1, 999_999] → Scope if raw % 10 ∈ {1,2,3}, else None
• All others (0, negative, gaps) → None

Because the bands are pairwise disjoint, no value can match more than one case. There is no residue-based disambiguation between bands.

Trait Implementations

impl Clone for VariableReference

fn clone(&self) -> VariableReference

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for VariableReference

impl Debug for VariableReference

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

Formats the value using the given formatter.

impl Eq for VariableReference

impl PartialEq for VariableReference

fn eq(&self, other: &VariableReference) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for VariableReference