Enum ModeActivationError 

pub enum ModeActivationError {
    NotRegistered(ModeId),
    MissingCapability {
        mode: ModeId,
        missing: CapabilitySet,
    },
    Conflict {
        mode: ModeId,
        active: ModeId,
    },
    UnregisteredDependency {
        mode: ModeId,
        dep: ModeId,
    },
    WrongKind {
        mode: ModeId,
    },
    LifecycleFailed {
        mode: ModeId,
        reason: String,
    },
    WrongOwnerMode {
        current: ModeId,
        local: &'static str,
        owner: &'static str,
    },
}

Why an activation failed.

Two routes, and they reach different places. The registry validates registration, kind, capabilities, conflicts and dependency presence synchronously before any lifecycle hook runs: those variants are the Err of activate_major / activate_minor, nothing ran, nothing was published, and the active set is unchanged. An error returned by on_activate (normally LifecycleFailed) arrives after the activate call has already returned Ok; it is published as ModeEvent::ModeActivationFailed and the host rolls back.

Variants

NotRegistered(ModeId)

mode is not in the registry. Either typo’d or not registered yet.

MissingCapability

Buffer lacks one or more capabilities the mode requires. missing is the bitfield of the absent capabilities (i.e. mode.required_capabilities() - buffer_capabilities).

Fields

mode: ModeId

The mode that could not activate.

missing: CapabilitySet

The required capabilities the buffer does not offer.

Conflict

Activating mode would conflict with active – a declared conflicts_with entry on either side. Raised when activating a minor (directly or via an implies cascade); the registry never auto-deactivates the other mode, so the caller must deactivate it and retry if the swap is wanted.

Fields

mode: ModeId

The mode being activated.

active: ModeId

The already-active mode it conflicts with.

UnregisteredDependency

mode declares an implies dependency on dep, but dep is not registered. Indicates a build-config bug (a feature crate registered the parent without its dependency).

Fields

mode: ModeId

The mode declaring the dependency.

dep: ModeId

The implied mode that is not registered.

WrongKind

Wrong kind: caller invoked activate_major on a minor mode or vice versa. Indicates a type-bug in the caller; the trait’s kind() answers what’s expected.

Fields

mode: ModeId

The mode whose kind did not match the call.

LifecycleFailed

A mode’s on_activate failed. The variant a mode constructs itself (with its own id and a human-readable reason) when setup cannot complete — return it rather than panicking.

Fields

mode: ModeId

The mode whose hook failed.

reason: String

Why, for the user and the log.

WrongOwnerMode

A mode tried to write a buffer-local owned by a different mode (M.3.2.a). Reserved for the checked ModeContext::set_local / remove_local surface the design describes (comparing T::OWNER_MODE against the activating mode’s id); that surface is not implemented, so nothing constructs this variant today. See BufferLocal.

Fields

current: ModeId

The currently-activating mode that attempted the write.

local: &'static str

The local’s display name (T::NAME).

owner: &'static str

The local’s declared owner mode (T::OWNER_MODE).

Trait Implementations

impl Clone for ModeActivationError

fn clone(&self) -> ModeActivationError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ModeActivationError

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

Formats the value using the given formatter.

impl Display for ModeActivationError

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

Formats the value using the given formatter.

impl Eq for ModeActivationError

impl Error for ModeActivationError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for ModeActivationError

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for ModeActivationError