Errors and Result

Beskid does not resurrect C# exceptions for breakfast. Recoverable failures are values you pattern-match, propagate with ?, and translate at boundaries.

Result and friends

Normative rules: Error handling.

• Model errors as enum variants (Ok / Err or domain-specific shapes).
• Option<T> is the optional type—there is no optional keyword.
• Postfix ? on a Result-like expression: success unwraps; Err returns or translates from the current function.

flowchart LR
  expr[Expression with Result type]
  q[Postfix ?]
  ok[Continue with success value]
  err[Return Err from enclosing callable]
  expr --> q
  q -->|Ok| ok
  q -->|Err| err

FFI and envelopes

At foreign boundaries, errors become ABI envelopes—no silent throw across the wall. See Interop contracts and Error and unwind semantics.

What you should do in application code

Practice	Why
Named error enums per domain	Callers can handle variants without string archaeology
? for happy-path plumbing	Less nesting than manual match everywhere
Translate at module boundaries	Keep internal Err types out of public APIs

Diagnostics

Type and flow mistakes surface as compiler diagnostics in the E16xx band (contract-related) and analysis rules tied to semantic pipeline.

Next

Contracts in source