Enum DebugStopReason 

pub enum DebugStopReason {
    Breakpoint {
        id: BreakpointId,
        name: String,
    },
    Watchpoint {
        global_idx: u32,
    },
    Choices,
    Step,
    AwaitingExternal,
    Terminal,
    NoStepOutTarget,
    NoLineInfo,
}

Why a debug_run/debug_step call stopped.

Variants

Breakpoint

An enabled breakpoint’s position was reached, checked before the matching instruction executed.

Fields

id: BreakpointId

name: String

Watchpoint

A watched global was written (debug_run_watching only).

Fields

global_idx: u32

Choices

A choice point was reached (vm::Stepped::Done with non-empty pending choices) — the flow is now WaitingForChoice, distinct from DebugStopReason::Terminal: unlike an actual -> DONE/ -> END, Story::choose followed by Story::continue_single can resume the story from here. Turn-index bump and invisible-default auto-select have already been applied (the same bookkeeping advance_with_limit performs on this outcome), so a caller that hands control back to the production API sees consistent state (issue #3186 review).

Step

The requested step (into/over/out) completed normally.

AwaitingExternal

Execution reached a bound external whose handler deferred (ExternalResult::Pending) — the External frame is left intact, exactly as FlowInstance::advance surfaces StepOutcome::AwaitingExternal (#3224). The host resolves it out-of-band (Story::resolve_external, or resolve_external_flow for a named flow), then resumes with any debug verb. Synchronously resolved externals and in-story fallbacks never surface this — the debug loops run them through exactly as production advance() does.

Terminal

The flow reached a terminal VM outcome (-> DONE/-> END, or content otherwise exhausted) before the requested stop condition — breakpoint, watchpoint, or step target — was reached.

NoStepOutTarget

StepMode::Out was requested from the outermost (Root) frame, which has no caller to return to — docs/debugger-spec.md §4: “The debugger must disable step-out… exactly as GDB disables finish in the outermost frame.” Reported instead of running the story to its own natural end, which would be a misleading way to answer “step out of a frame with no caller.”

NoLineInfo

A line-granular step was requested but the artifact cannot say which line execution is on — no DebugInfo, or a file compiled without source text so it carries no line index (#3264, #3261).

Reported rather than silently degrading to instruction stepping: handing someone four-presses-per-line when they asked to advance one line is how a missing line index becomes a mystery instead of a legible “this build has no line info”. Mirrors Self::NoStepOutTarget’s posture — a verb that has nothing to do here says so.

Trait Implementations

impl Clone for DebugStopReason

fn clone(&self) -> DebugStopReason

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for DebugStopReason

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

Formats the value using the given formatter.

impl Eq for DebugStopReason

impl PartialEq for DebugStopReason

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for DebugStopReason