rust-lang / rust-lang/rust-clippy
`cast_precision_loss` is a bit misleading for `float`s
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Description
Description
I have this code
#[warn(clippy::cast_precision_loss)]
fn div_usize_as_f64(n: usize, d: usize) -> f64 {
n as f64 / d as f64
}
I get the following msg
warning: casting `usize` to `f64` causes a loss of precision on targets with 64-bit wide pointers (`usize` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
"mantissa is 52bits" is true, but the implicit bit makes the "effective mantissa" 53b instead. I suggest making the message "more correct" by saying something like "maximum f64 value is 2u64.pow(53) - 1"
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Research direction
The issue identifies Rust Clippy's cast_precision_loss lint and the warning text that is misleading for f64. Start by locating that lint and its diagnostic or UI test coverage; done means the wording accurately reflects effective f64 precision and the relevant test expectations pass.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 42/100