Lint to prevent people from indexing a string via iterator.nth(i)

[sebschmi]

What it does

It is possible to access the nth byte of a string using string.bytes().nth(i). But in case of i = 0 this collides with the lint iter-nth-zero.
Alternatively one could write string.as_bytes().get(1), which does not produce any clippy warnings. This code is equivalent to the code above in what it does.

Categories (optional)

• Kind: maybe clippy::style and maybe clippy::pedantic. Maybe also clippy::perf.

Advantages

• Does not wrongly warn about iter-nth-zero when accessing the first byte of a string
• Does not rely on the compiler to optimise out the iteration when doing direct indexed access

Drawbacks

The iteration is very easy for the compiler to optimise out, so that argument is weak.
The argument about iter-nth-zero is valid but it might be better to patch iter-nth-zero instead of teaching people how to code around the drawbacks of iter-nth-zero.

Maybe iter-nth-zero should become pedantic instead?

Example

string.bytes().nth(i)

Could be written as:

string.as_bytes().get(i)

[TaKO8Ki]

Can I tackle this issue?

[giraffate]

I think you can take this.

[TaKO8Ki]

I'm going to tackle this issue soon.

[TaKO8Ki]

@rustbot claim