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clippy: fix cast_lossless lint #71

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clippy: fix cast_lossless lint #71

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6 changes: 6 additions & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ repository = "https://github.com/rust-lang/rustc-hash"
edition = "2021"
rust-version = "1.77"

[workspace.lints.clippy]
cast_lossless = "warn"

@scottmcm scottmcm Jul 24, 2026

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Given the number of other as casts here anyway, I don't see much value in this. The lint is pedantic for a reason; if you want to "fix" a pedantic lint I think you need better justification than what it says in the lint, since that wasn't enough to make it warn-by-default even in clippy.


[features]
default = ["std"]
std = []
Expand All @@ -18,3 +21,6 @@ rand = ["dep:rand", "std"]

[dependencies]
rand = { version = "0.9", optional = true }

[lints]
workspace = true
14 changes: 7 additions & 7 deletions src/lib.rs
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Expand Up @@ -215,7 +215,7 @@ fn multiply_mix(x: u64, y: u64) -> u64 {
)) {
// We compute the full u64 x u64 -> u128 product, this is a single mul
// instruction on x86-64, one mul plus one mulhi on ARM64.
let full = (x as u128).wrapping_mul(y as u128);
let full = u128::from(x).wrapping_mul(u128::from(y));
let lo = full as u64;
let hi = (full >> 64) as u64;
Comment on lines -218 to 220

@scottmcm scottmcm Jul 24, 2026

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If you want to change something here, I think a much better change would to stop needing all the explicit widening and narrowing in the first place.

The fix for the ases here isn't from, IMHO, but something more like

let (lo, hi) = x.carrying_mul(y, 0);


Expand All @@ -239,8 +239,8 @@ fn multiply_mix(x: u64, y: u64) -> u64 {
let hy = (y >> 32) as u32;

// u32 x u32 -> u64 the low bits of one with the high bits of the other.
let afull = (lx as u64).wrapping_mul(hy as u64);
let bfull = (hx as u64).wrapping_mul(ly as u64);
let afull = u64::from(lx).wrapping_mul(u64::from(hy));
let bfull = u64::from(hx).wrapping_mul(u64::from(ly));

// Combine, swapping low/high of one of them so the upper bits of the
// product of one combine with the lower bits of the other.
Expand Down Expand Up @@ -271,14 +271,14 @@ fn hash_bytes(bytes: &[u8]) -> u64 {
s0 ^= u64::from_le_bytes(bytes[0..8].try_into().unwrap());
s1 ^= u64::from_le_bytes(bytes[len - 8..].try_into().unwrap());
} else if len >= 4 {
s0 ^= u32::from_le_bytes(bytes[0..4].try_into().unwrap()) as u64;
s1 ^= u32::from_le_bytes(bytes[len - 4..].try_into().unwrap()) as u64;
s0 ^= u64::from(u32::from_le_bytes(bytes[0..4].try_into().unwrap()));
s1 ^= u64::from(u32::from_le_bytes(bytes[len - 4..].try_into().unwrap()));
} else if len > 0 {
let lo = bytes[0];
let mid = bytes[len / 2];
let hi = bytes[len - 1];
s0 ^= lo as u64;
s1 ^= ((hi as u64) << 8) | mid as u64;
s0 ^= u64::from(lo);
s1 ^= (u64::from(hi) << 8) | u64::from(mid);
}
} else {
// Handle bulk (can partially overlap with suffix).
Expand Down
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