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Fix an incorrect error message regarding the size of isize and usize

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This commit is contained in:
Nelli Skogman 2025-10-12 16:07:11 +02:00
parent 6885741e18
commit a287c66721
4 changed files with 25 additions and 33 deletions
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22
clippy_lints/src/casts/cast_precision_loss.rs
View file

@ -23,15 +23,11 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, ca
let cast_to_f64 = to_nbits == 64;
let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
let arch_dependent_str = "on targets with 64-bit wide pointers ";
let from_nbits_str = if arch_dependent {
"64".to_owned()
} else if is_isize_or_usize(cast_from) {
// FIXME: handle 16 bits `usize` type
"32 or 64".to_owned()
let has_width = if is_isize_or_usize(cast_from) {
"can be up to 64 bits wide depending on the target architecture".to_owned()
} else {
from_nbits.to_string()
format!("is {from_nbits} bits wide")
};
span_lint(
@ -39,13 +35,9 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, ca
CAST_PRECISION_LOSS,
expr.span,
format!(
"casting `{0}` to `{1}` causes a loss of precision {2}(`{0}` is {3} bits wide, \
but `{1}`'s mantissa is only {4} bits wide)",
cast_from,
if cast_to_f64 { "f64" } else { "f32" },
if arch_dependent { arch_dependent_str } else { "" },
from_nbits_str,
mantissa_nbits
"casting `{cast_from}` to `{cast_to}` may cause a loss of precision \
(`{cast_from}` {has_width}, \
but `{cast_to}`'s mantissa is only {mantissa_nbits} bits wide)",
),
);
}

12
tests/ui/cast.stderr
View file

@ -1,4 +1,4 @@
error: casting `i32` to `f32` causes a loss of precision (`i32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `i32` to `f32` may cause a loss of precision (`i32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast.rs:23:5
|
LL | x0 as f32;
@ -7,31 +7,31 @@ LL | x0 as f32;
= note: `-D clippy::cast-precision-loss` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::cast_precision_loss)]`
error: casting `i64` to `f32` causes a loss of precision (`i64` is 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `i64` to `f32` may cause a loss of precision (`i64` is 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast.rs:27:5
|
LL | x1 as f32;
| ^^^^^^^^^
error: casting `i64` to `f64` causes a loss of precision (`i64` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
error: casting `i64` to `f64` may cause a loss of precision (`i64` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast.rs:30:5
|
LL | x1 as f64;
| ^^^^^^^^^
error: casting `u32` to `f32` causes a loss of precision (`u32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `u32` to `f32` may cause a loss of precision (`u32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast.rs:34:5
|
LL | x2 as f32;
| ^^^^^^^^^
error: casting `u64` to `f32` causes a loss of precision (`u64` is 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `u64` to `f32` may cause a loss of precision (`u64` is 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast.rs:38:5
|
LL | x3 as f32;
| ^^^^^^^^^
error: casting `u64` to `f64` causes a loss of precision (`u64` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
error: casting `u64` to `f64` may cause a loss of precision (`u64` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast.rs:41:5
|
LL | x3 as f64;

12
tests/ui/cast_size.r32bit.stderr
View file

@ -13,7 +13,7 @@ LL - 1isize as i8;
LL + i8::try_from(1isize);
|
error: casting `isize` to `f32` causes a loss of precision (`isize` is 32 or 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `isize` to `f32` may cause a loss of precision (`isize` can be up to 64 bits wide depending on the target architecture, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast_size.rs:24:5
|
LL | x0 as f32;
@ -22,19 +22,19 @@ LL | x0 as f32;
= note: `-D clippy::cast-precision-loss` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::cast_precision_loss)]`
error: casting `usize` to `f32` causes a loss of precision (`usize` is 32 or 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `usize` to `f32` may cause a loss of precision (`usize` can be up to 64 bits wide depending on the target architecture, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast_size.rs:26:5
|
LL | x1 as f32;
| ^^^^^^^^^
error: casting `isize` to `f64` causes a loss of precision on targets with 64-bit wide pointers (`isize` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
error: casting `isize` to `f64` may cause a loss of precision (`isize` can be up to 64 bits wide depending on the target architecture, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast_size.rs:28:5
|
LL | x0 as f64;
| ^^^^^^^^^
error: 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)
error: casting `usize` to `f64` may cause a loss of precision (`usize` can be up to 64 bits wide depending on the target architecture, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast_size.rs:30:5
|
LL | x1 as f64;
@ -165,13 +165,13 @@ error: casting `u32` to `isize` may wrap around the value on targets with 32-bit
LL | 1u32 as isize;
| ^^^^^^^^^^^^^
error: casting `i32` to `f32` causes a loss of precision (`i32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `i32` to `f32` may cause a loss of precision (`i32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast_size.rs:61:5
|
LL | 999_999_999 as f32;
| ^^^^^^^^^^^^^^^^^^
error: 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)
error: casting `usize` to `f64` may cause a loss of precision (`usize` can be up to 64 bits wide depending on the target architecture, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast_size.rs:63:5
|
LL | 9_999_999_999_999_999usize as f64;

12
tests/ui/cast_size.r64bit.stderr
View file

@ -13,7 +13,7 @@ LL - 1isize as i8;
LL + i8::try_from(1isize);
|
error: casting `isize` to `f32` causes a loss of precision (`isize` is 32 or 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `isize` to `f32` may cause a loss of precision (`isize` can be up to 64 bits wide depending on the target architecture, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast_size.rs:24:5
|
LL | x0 as f32;
@ -22,19 +22,19 @@ LL | x0 as f32;
= note: `-D clippy::cast-precision-loss` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::cast_precision_loss)]`
error: casting `usize` to `f32` causes a loss of precision (`usize` is 32 or 64 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `usize` to `f32` may cause a loss of precision (`usize` can be up to 64 bits wide depending on the target architecture, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast_size.rs:26:5
|
LL | x1 as f32;
| ^^^^^^^^^
error: casting `isize` to `f64` causes a loss of precision on targets with 64-bit wide pointers (`isize` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
error: casting `isize` to `f64` may cause a loss of precision (`isize` can be up to 64 bits wide depending on the target architecture, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast_size.rs:28:5
|
LL | x0 as f64;
| ^^^^^^^^^
error: 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)
error: casting `usize` to `f64` may cause a loss of precision (`usize` can be up to 64 bits wide depending on the target architecture, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast_size.rs:30:5
|
LL | x1 as f64;
@ -165,13 +165,13 @@ error: casting `u32` to `isize` may wrap around the value on targets with 32-bit
LL | 1u32 as isize;
| ^^^^^^^^^^^^^
error: casting `i32` to `f32` causes a loss of precision (`i32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
error: casting `i32` to `f32` may cause a loss of precision (`i32` is 32 bits wide, but `f32`'s mantissa is only 23 bits wide)
--> tests/ui/cast_size.rs:61:5
|
LL | 999_999_999 as f32;
| ^^^^^^^^^^^^^^^^^^
error: 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)
error: casting `usize` to `f64` may cause a loss of precision (`usize` can be up to 64 bits wide depending on the target architecture, but `f64`'s mantissa is only 52 bits wide)
--> tests/ui/cast_size.rs:63:5
|
LL | 9_999_999_999_999_999usize as f64;