Rust Edition 2024 to 2021 Downgrade

Problem

When downgrading a Rust project from edition 2024 to 2021, compilation fails with "let chains are only allowed in Rust 2024 or later" errors. Let chains are a Rust 2024 feature that allows combining multiple let patterns with && in if expressions.

Context / Trigger Conditions

• Error message: error: let chains are only allowed in Rust 2024 or later
• Changing edition = "2024" to edition = "2021" in Cargo.toml
• Code contains patterns like if let Some(x) = foo() && let Some(y) = bar() { ... }
• Multiple files affected (let chains may be used extensively throughout codebase)

Solution

Step 1: Identify all let chains

grep -r "&& let " --include="*.rs" .