unnecessary_string_to_bytes

Default Severity: warn

What it does

Detects unnecessary .to_bytes() calls on the Soroban String object.

Why is this bad?

DANGER

Converting a soroban_sdk::String to Bytes via .to_bytes() creates a new host-backed object, which incurs unnecessary CPU and memory costs. In many cases, String can be used directly where Bytes is accepted, such as in storage operations.

Example

// ❌ Bad: unnecessary conversion from String to Bytes
let key = String::from_str(&env, "foo");
let key_bytes = key.to_bytes();
env.storage().instance().set(&key_bytes, &value);

Suggested Fix

TIP

Use the String directly where Bytes is accepted, or construct Bytes directly using Bytes::from_slice() instead of converting from a String.

// ✅ Good: use String directly
let key = String::from_str(&env, "foo");
env.storage().instance().set(&key, &value);

// ✅ Also good: construct Bytes directly
let key = Bytes::from_slice(&env, b"foo");
env.storage().instance().set(&key, &value);