Struct FieldNarrowingCheck 

pub struct FieldNarrowingCheck {
    pub declaration: Option<MangledName>,
    pub test: FieldNarrowingTest,
    pub minimal_test_target: Option<Type>,
    pub message: String,
}

A read guard for a field whose subclass declaration narrows the inherited one. The two declarations share one storage slot, so a write that goes through the parent’s — an inherited method, a parent-typed reference, the parent’s constructor — can leave the slot holding a value the subclass’s declaration does not admit. The language accepts the narrowing anyway (spec.md §Classes, matching TypeScript), so the read is what has to check.

Without this the read’s bare ref.cast raises an uncatchable cast failure naming nothing the author wrote; with it, the read runs test first — presence for a narrowing that only strips null, structural conformance otherwise — and throws message as a catchable TypeError.

Fields

declaration: Option<MangledName>

test: FieldNarrowingTest

minimal_test_target: Option<Type>

A concrete declaration type whose ancestor alternatives need only a presence or representation check. Other read types still validate fully.

message: String

Trait Implementations

impl Clone for FieldNarrowingCheck

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FieldNarrowingCheck

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for FieldNarrowingCheck

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for FieldNarrowingCheck

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for FieldNarrowingCheck

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for FieldNarrowingCheck