---
title: Rust Result leaves recovery policy to the caller
slug: rust-error-handling-result
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source: https://iinventedlight.com/library/notes/rust-error-handling-result.md
source_license: MIT
attribution: Original synthesis by iinventedlight, drafted by Librarian with AI assistance; based on the attributed sources
  below.
author: Librarian
client: Librarian
date: '2026-11-05'
checked_on: '2026-11-05'
as_of: '2026-11-05'
status: published
confidence: medium
category: coding-references
tags:
- rust
- error
- handling
untested: Reference note. No code or commands were run to validate behavior.
sources:
- id: S1
  title: Recoverable errors with Result
  publisher: The Rust Project Developers
  url: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html
  accessed: '2026-11-05'
  license: MIT
  license_url: https://raw.githubusercontent.com/rust-lang/book/main/LICENSE-MIT
  license_verified: '2026-11-05'
  green: true
  attribution: The Rust Project Developers; Recoverable errors with Result; MIT
  snapshot: _fetched/rust-result.txt
- id: S2
  title: To panic or not to panic
  publisher: The Rust Project Developers
  url: https://doc.rust-lang.org/book/ch09-03-to-panic-or-not-to-panic.html
  accessed: '2026-11-05'
  license: MIT
  license_url: https://raw.githubusercontent.com/rust-lang/book/main/LICENSE-MIT
  license_verified: '2026-11-05'
  green: true
  attribution: The Rust Project Developers; To panic or not to panic; MIT
  snapshot: _fetched/rust-panic.txt
---
# Rust Result leaves recovery policy to the caller

## Summary
`Result<T, E>` represents either a successful value or an error. Its `Ok` and `Err` variants let a function report failure without deciding that the program must stop. [S1, S2]

## Details
The Rust Book uses `File::open` to show why the success value and error value need different types. Returning `Result` lets the caller recover, forward the error, or decide that failure is unrecoverable. The Book recommends that choice as the default for a function that may fail, while allowing panics in cases such as examples and prototypes. [S1, S2]

## Claims
- id: C1
  claim: "Result has Ok and Err variants."
  source: S1
  evidence: "two\nvariants, Ok and Err"
- id: C2
  claim: "The success value is carried in Ok."
  source: S1
  evidence: "a success case within the Ok variant"
- id: C3
  claim: "Returning Result gives calling code a choice about recovery."
  source: S2
  evidence: "you give the\ncalling code options"

## Sources
- [S1] Recoverable errors with Result. The Rust Project Developers. https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html. MIT; license: https://raw.githubusercontent.com/rust-lang/book/main/LICENSE-MIT. Accessed 2026-11-05.
- [S2] To panic or not to panic. The Rust Project Developers. https://doc.rust-lang.org/book/ch09-03-to-panic-or-not-to-panic.html. MIT; license: https://raw.githubusercontent.com/rust-lang/book/main/LICENSE-MIT. Accessed 2026-11-05.

## Attribution and notices
This note is CC BY 4.0. Source material has been condensed and restated; short evidence excerpts retain their source license.

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