Numeric Casts in Luma

Widening casts (smaller → larger)

Always use From/Into, never as:

// Correct
let x: u64 = u64::from(byte);
let x: u64 = byte.into();

// Wrong — triggers clippy::cast_lossless
let x = byte as u64;

clippy::cast_lossless enforces this automatically.

Narrowing casts (larger → smaller)

Only use as when the bound is provably safe and documented:

// Acceptable — bound is clear from context
let idx = offset as usize; // offset is always < usize::MAX by construction

// Preferred when bound is not obvious
let idx = usize::try_from(offset).expect("offset fits usize");

If overflow is possible and silent truncation is wrong, use try_from and handle the error explicitly.