Error model specification

Decision summary

• No exceptions and no hidden control flow.
• Errors are expressed explicitly as Option[T] (per language spec).
• Runtime panic is reserved for unrecoverable faults.

Scope

This chapter defines runtime-side failure behavior at execution boundaries. Language-level error typing remains canonical in docs/spec/error-handling.md.

Error propagation

• Functions return Option[T] when errors are expected.
• Callers must explicitly handle none.
• No implicit propagation (?-style) unless the language introduces a specific operator later.

Panic behavior

• panic(msg) is a runtime builtin.
• Lowering inserts a call to panic for unrecoverable runtime conditions (e.g., bounds checks if enabled).
• panic terminates execution (trap).

Diagnostics

• Compile-time errors are reported via semantic diagnostics (HIR stage).
• Runtime errors use panic with message + span context when possible.

Non-goals

• Defining source-language syntax for error handling forms.
• Defining build/deployment policy for backend artifacts.