rust-lang/rust-clippy

don't fold(..) an Option when you can map_or(..)

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#1658 opened on Apr 3, 2017

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 (2 comments) (0 reactions) (0 assignees)Rust (10,406 stars) (1,391 forks)batch import
A-lintL-styleT-middlegood first issue

Description

catch my_option.iter().fold(my_val, |x, y| ..y), suggest my_option.map_or(my_val, |x| ..my_val)

Contributor guide

Tech stack
rust
Domain
toolingdeveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic Rust knowledgefamiliarity with clippy lint creation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Review existing clippy lints that suggest alternative method calls (e.g., 'manual map' or 'option if let and matches') as templates. The lint should detect the pattern `option.iter().fold(init, |x, y| ...)` and suggest `option.map or(init, |x| ...)`. Key files: clippy lints/src/methods/ and clippy utils/src/ for utility functions. The official Clippy contributing guide (doc/adding lints.md) provides step by step instructions. Check comments for any prior discussion on implementation details.