Enum FMError 

#[non_exhaustive]
pub enum FMError {
    ModelUnavailable {
        reason: Unavailability,
        message: String,
    },
    GuardrailViolation(String),
    ContextWindowExceeded(String),
    UnsupportedLanguage(String),
    AssetsUnavailable(String),
    RateLimited(String),
    DecodingFailure(String),
    Refusal(String),
    ConcurrentRequests(String),
    UnsupportedGuide(String),
    ToolCallFailed(String),
    AdapterInvalidAsset(String),
    AdapterInvalidName(String),
    AdapterCompatibleNotFound(String),
    Cancelled,
    InvalidArgument(String),
    Unknown {
        code: i32,
        message: String,
    },
}

Top-level error type returned by all fallible APIs in this crate.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

ModelUnavailable

FoundationModels is not available on this device.

See Unavailability for the specific reason.

Fields

reason: Unavailability

message: String

GuardrailViolation(String)

The model refused to produce a response because the prompt or generated content tripped a safety guardrail.

ContextWindowExceeded(String)

The combined prompt + history exceeds the model’s context window.

UnsupportedLanguage(String)

The requested locale or language is not supported by the on-device model.

AssetsUnavailable(String)

On-device model assets are still downloading or otherwise unavailable.

RateLimited(String)

The session was rate-limited (typically only relevant on Mac with extended generation budgets).

DecodingFailure(String)

Structured generation failed to decode the model’s output into the requested Generable schema.

Refusal(String)

The model refused the request (distinct from a guardrail violation — the model itself declined to answer).

ConcurrentRequests(String)

Too many concurrent generation requests against the same session.

UnsupportedGuide(String)

The supplied crate::schema::GenerationGuide is unsupported by the on-device model.

ToolCallFailed(String)

A tool invocation failed while the model was using Tool calling.

AdapterInvalidAsset(String)

An adapter asset pack was invalid.

AdapterInvalidName(String)

The requested adapter name was invalid.

AdapterCompatibleNotFound(String)

No compatible adapter could be found for the requested name.

Cancelled

The generation Task was cancelled before completion.

InvalidArgument(String)

An invalid argument crossed the FFI boundary (e.g. a NUL byte in a prompt).

Unknown

Catch-all for unmapped Swift errors. Inspect code and message for diagnostics.

Fields

code: i32

message: String

Implementations

impl FMError

pub const fn code(&self) -> i32

Numeric status code reported by the Swift bridge. Useful for matching against crate::ffi::status constants.

pub fn message(&self) -> &str

Human-readable description (forwarded from Error.localizedDescription).

pub fn generation_error_context(&self) -> Option<GenerationErrorContext>

Structured generation-error context, when available.

pub fn adapter_asset_error_context(&self) -> Option<AdapterAssetErrorContext>

Structured adapter-asset error context, when available.

pub fn schema_error_context(&self) -> Option<SchemaErrorContext>

Structured schema-error context, when available.

pub fn recovery_suggestion(&self) -> Option<String>

Localized recovery suggestion, when the SDK provided one.

pub fn failure_reason(&self) -> Option<String>

Localized failure reason, when the SDK provided one.

pub fn refusal(&self) -> Option<Refusal>

Typed refusal helper, when this error came from a refusal.

pub fn tool_call_error(&self) -> Option<ToolCallError>

Typed tool-call failure metadata, when available.

Trait Implementations

impl Clone for FMError

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 FMError

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

Formats the value using the given formatter.

impl Display for FMError

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

Formats the value using the given formatter.

impl Eq for FMError

impl Error for FMError

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 FMError

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