Enum Fault 

pub enum Fault {
    DivideByZero,
    RegisterOutOfRange {
        reg: u8,
        frame_size: u8,
    },
    RegisterIndexOverflow {
        base: u8,
        offset: u8,
    },
    BadConstant {
        index: u32,
        pool_size: u32,
    },
    BadFunction {
        index: u32,
        table_size: u32,
    },
    BadOpcodeByte(u8),
    CallStackOverflow {
        depth: usize,
    },
    TypeMismatch {
        expected: &'static str,
        got: &'static str,
    },
    BadNative {
        index: u32,
        table_size: u32,
    },
    NativeError(String),
    NativeDenied(String),
    Explicit(i32),
    Invariant(&'static str),
}

Anything that can go wrong inside a running Flow’s VM.

A Fault is never a Rust panic — panics are reserved for genuine host bugs and are caught at the worker boundary (see crate::scheduler::worker) precisely so that one Flow’s bug (division by zero, a corrupt jump target that slipped past the verifier, an out-of-range register) can never take down a worker thread, let alone the whole runtime. A Fault instead becomes crate::FlowOutcome::Failed and is handed to the Flow’s supervisor, which decides whether to restart it (design notes §15-16).

Variants

DivideByZero

RegisterOutOfRange

Fields

reg: u8

frame_size: u8

RegisterIndexOverflow

An instruction’s register operand plus the offset it gathers at does not fit the register index space at all — e.g. Spawn a=255, which reads its arguments from a+1...

Distinct from Fault::RegisterOutOfRange, which is about an index that is perfectly representable and merely absent from this frame. Kept separate so the fault cannot lie: reporting “register 255 is out of range” for a request that was really for register 256 would send whoever reads it looking in the wrong place.

Fields

base: u8

offset: u8

BadConstant

Fields

index: u32

pool_size: u32

BadFunction

Fields

index: u32

table_size: u32

BadOpcodeByte(u8)

CallStackOverflow

Function call nesting exceeded Vm::MAX_CALL_DEPTH. Bytecode has no native stack overflow (frames are heap-allocated Vec<Value>s), so this is a deliberate, checked limit rather than a segfault.

Fields

depth: usize

TypeMismatch

Fields

expected: &'static str

got: &'static str

BadNative

CallNative referenced a slot outside the runtime’s registered native function table (design notes §30-31). Distinct from BadFunction, which is about the bytecode function table baked into the chunk — natives are supplied by the embedder at Vm construction time and can’t be range-checked by crate::bytecode::verify, which has no visibility into them.

Fields

index: u32

table_size: u32

NativeError(String)

A native function returned an error (host-side failure — I/O, invalid argument the Rust side rejected, capability denied, etc). The message is native-function-defined. Host-side native refused the call (FFI error string).

NativeDenied(String)

S7: CALL_NATIVE failed the allowlist / NATIVE-right / revocation check before the function pointer was touched.

Explicit(i32)

Explicit Trap opcode, e.g. an assertion emitted by a compiler.

Invariant(&'static str)

Broken VM invariant (e.g. empty frame stack while running). Category D in the error model — surfaced as a Flow fault, never as unwrap.

Trait Implementations

impl Clone for Fault

fn clone(&self) -> Fault

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Fault

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

Formats the value using the given formatter.

impl Display for Fault

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

Formats the value using the given formatter.

impl Eq for Fault

impl Error for Fault

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 From<Fault> for SpawnError

fn from(fault: Fault) -> Self

Converts to this type from the input type.

impl PartialEq for Fault

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Fault