Enum Substitute 

pub enum Substitute {
    TypeDefault(Produced),
    Ours(Produced),
    NoValue,
    FromSiblings,
}

What this crate’s reader hands back where the engine’s answer names no value.

This crate’s answer, not the engine’s. Recording it stops a reader inventing a number in an unwrap_or beside an entry that says no value is known, which is how twelve non-obvious literals came to sit in readers with nothing recording them.

Variants

TypeDefault(Produced)

The field’s Rust type decided, so a rebuild regenerates it.

Carries the value anyway. A consumer that can name the state but not the value has only “the type decides” to print, which is a cell with nothing in it.

Ours(Produced)

A specific value this layer chose. Not an engine fact.

NoValue

There is nothing to substitute: the model holds the absence itself, so a reader hands back “not there” rather than a stand-in.

FromSiblings

The reader works it out from sibling fields, and this deliberately does not model how.

Silence::NotAConstant refuses the same thing on the engine’s side, for the same reason: encoding a derivation would put a small expression language in a static table to serve a handful of fields. Three entries need it. The derivation lives in the view’s own reader, where it can be read as code.

Trait Implementations

impl Clone for Substitute

fn clone(&self) -> Substitute

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Substitute

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

Formats the value using the given formatter.

impl PartialEq for Substitute

fn eq(&self, other: &Substitute) -> 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 Copy for Substitute

impl StructuralPartialEq for Substitute