lint unnecessary literal casts

[euclio]

What it does

Lints unnecessary as-casts of literals when they could be written using literal syntax.

Categories (optional)

• Kind: clippy::style

What is the advantage of the recommended code over the original code

• Avoids accidental truncation
• Uses syntax dedicated to this purpose

Drawbacks

None.

Example

1 as u32

Could be written as:

1u32

[leonardo-m]

Better to suggest: 1_u32

[ebroto]

This would be currently linted by as_conversions (playground). The docs imply it's allow-by-default because it has false positives.

The lint could be improved though to generate suggestions as the one you gave.

[euclio]

I think the lints serve different purposes. I 1 as u32 is almost certainly a mistake, while there are legitimate uses of as casts in general (which is why it's allow-by-default).

[flip1995]

Yes as_conversions is a restriction lint, with the design that it lints all as conversions, regardless what it converts.

[geoffreycopin]

Hi, I'd be glad to give this a shot !

[geoffreycopin]

When testing my implementation, I noticed that there is some overlap with a previously existing lint that flags int literals that are casted to a float type.

Would it be suitable to just extend the aforementioned lint so that it become "casting number literal to <cast_to> is unnecessary" ? If not, what would be a good way to handle the overlap ?

[ebroto]

@geoffreycopin I think what you suggest makes sense as that lint was already extended in #3842 to add the float cases.

Even if later there's a decision to not enhance that lint, your code should go in that module to be able to handle the overlap.

[ebroto]

Fixed by #6187