Errors and Result

Informative guide. This Book page explains Beskid but does not define the standard. For normative requirements, use the Beskid Standard.

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
  accTitle: Postfix question mark on a Result
  accDescr: A Result expression passes through the postfix question mark: Ok continues with the success value and Err returns from the enclosing callable.
  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