False positive: needless_range_loop

Summary

Related code:

for i in 0..message.len() {
        block.data[i] = message[i] as char;
 }

Clippy begs me to use rust for x in data
without the 'i' enumerator, however this would make fetching message[i] impossible.

Lint Name

needless_range_loop

Reproducer

I tried this code:

for i in 0..message.len() {
        block.data[i] = message[i] as char;
}

I saw this happen:

the loop variable `i` is used to index `message` Help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_range_loop Help: consider using an iterator and enumerate()

I expected to see this happen:

no complaints from Clippy

Version

rustc 1.72.0-nightly (8c74a5d27 2023-06-14)
binary: rustc
commit-hash: 8c74a5d27c644a0f7a22bb2fa8dd3ff8257bc220
commit-date: 2023-06-14
host: x86_64-pc-windows-msvc
release: 1.72.0-nightly
LLVM version: 16.0.5

Additional Labels

No response

Start with the needless_range_loop lint and reproduce the reported Rust example to understand why it is flagged. Trace the lint's handling of indexed loops, then add or update a focused regression test showing the expected behavior; done means the valid use of message[i] no longer produces this false positive.