Enum CompatibilityVerdict 

pub enum CompatibilityVerdict {
    Identical,
    WireCompatible,
    AppendSafe,
    MigrationRequired,
    Incompatible,
}

Unified compatibility verdict between two layout versions.

Replaces ad-hoc boolean checks with a single, ranked classification. The ordering is from least disruptive to most disruptive.

Variants

Identical

Layouts are byte-identical (same layout_id).

WireCompatible

Same wire layout (field count, sizes, offsets, types all match) but layout_id differs. Semantic metadata changed (e.g. field intent, layout name). Safe to read, no migration needed.

AppendSafe

Same discriminator, old field prefix intact in new layout. Old readers can still parse new accounts (they ignore the tail). Covers both strict append (new fields only at the end) and prefix-preserving changes. No forced migration required.

MigrationRequired

Breaking change: field types changed, fields removed, or prefix altered. Full migration required before deploying new code.

Incompatible

Different discriminators. These are fundamentally different types.

Implementations

impl CompatibilityVerdict

pub fn between(older: &LayoutManifest, newer: &LayoutManifest) -> Self

Compute the verdict for a version transition.

pub const fn name(self) -> &'static str

Human-readable name.

pub const fn is_safe(self) -> bool

Whether the transition is safe without any migration.

pub const fn is_backward_readable(self) -> bool

Whether old readers can still parse accounts written by the new layout.

pub const fn requires_migration(self) -> bool

Whether a migration instruction is required.

pub fn refine_with_roles<const N: usize>( self, report: &SegmentMigrationReport<N>, ) -> Self

Refine a verdict using segment-role information.

The base between() is field-level only. When a segmented account has role metadata, this method can soften or escalate:

• A MigrationRequired verdict is softened to AppendSafe when all changed segments are clearable or rebuildable (Cache, Index, Journal). Core / Audit / Extension changes stay breaking.

• An AppendSafe verdict is escalated to MigrationRequired when any modified segment is immutable-after-init (Audit).

Trait Implementations

impl Clone for CompatibilityVerdict

fn clone(&self) -> CompatibilityVerdict

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CompatibilityVerdict

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

Formats the value using the given formatter.

impl Display for CompatibilityVerdict

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

Formats the value using the given formatter.

impl PartialEq for CompatibilityVerdict

fn eq(&self, other: &CompatibilityVerdict) -> 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 CompatibilityVerdict

impl Eq for CompatibilityVerdict

impl StructuralPartialEq for CompatibilityVerdict