Hover 'pub const MAX: Self = -1' for i128::MAX

[UseK]

rust-analyzer version: rust-analyzer version: 0.3.2237-standalone (59bc7b4 2024-12-29)
rustc version: rustc 1.83.0 (90b35a623 2024-11-26)
editor or extension: VSCode 1.96.2, Zed 0.167.1
relevant settings: Nothing in particular
repository link (if public, optional): (eg. rust-analyzer)
code snippet to reproduce:

let x = i128::MAX;

I use hover function to 'MAX' part and expect:

pub const MAX: Self = 170141183460469231731687303715884105727

But it shows:

pub const MAX: Self = -1

related issues: #18116

[Veykril]

We don't seem to handle the bitshift here?

[Veykril]

Ah, the code here does all the integer math on i128 which is obviously wrong for unsigned ones

rust-analyzer/crates/hir-ty/src/mir/eval.rs

Lines 1341 to 1406 in 7e639ee

	} else {
	let is_signed = matches!(ty.as_builtin(), Some(BuiltinType::Int(_)));
	let l128 = i128::from_le_bytes(pad16(lc, is_signed));
	let r128 = i128::from_le_bytes(pad16(rc, is_signed));
	let check_overflow = |r: i128| {
	// FIXME: this is not very correct, and only catches the basic cases.
	let r = r.to_le_bytes();
	for &k in &r[lc.len()..] {
	if k != 0 && (k != 255 || !is_signed) {
	return Err(MirEvalError::Panic(format!("Overflow in {op:?}")));
	}
	}
	Ok(Owned(r[0..lc.len()].into()))
	};
	match op {
	BinOp::Ge | BinOp::Gt | BinOp::Le | BinOp::Lt | BinOp::Eq | BinOp::Ne => {
	let r = op.run_compare(l128, r128) as u8;
	Owned(vec![r])
	}
	BinOp::BitAnd
	| BinOp::BitOr
	| BinOp::BitXor
	| BinOp::Add
	| BinOp::Mul
	| BinOp::Div
	| BinOp::Rem
	| BinOp::Sub => {
	let r = match op {
	BinOp::Add => l128.overflowing_add(r128).0,
	BinOp::Mul => l128.overflowing_mul(r128).0,
	BinOp::Div => l128.checked_div(r128).ok_or_else(|| {
	MirEvalError::Panic(format!("Overflow in {op:?}"))
	})?,
	BinOp::Rem => l128.checked_rem(r128).ok_or_else(|| {
	MirEvalError::Panic(format!("Overflow in {op:?}"))
	})?,
	BinOp::Sub => l128.overflowing_sub(r128).0,
	BinOp::BitAnd => l128 & r128,
	BinOp::BitOr => l128 | r128,
	BinOp::BitXor => l128 ^ r128,
	_ => unreachable!(),
	};
	check_overflow(r)?
	}
	BinOp::Shl | BinOp::Shr => {
	let r = 'b: {
	if let Ok(shift_amount) = u32::try_from(r128) {
	let r = match op {
	BinOp::Shl => l128.checked_shl(shift_amount),
	BinOp::Shr => l128.checked_shr(shift_amount),
	_ => unreachable!(),
	};
	if shift_amount as usize >= lc.len() * 8 {
	return Err(MirEvalError::Panic(format!(
	"Overflow in {op:?}"
	)));
	}
	if let Some(r) = r {
	break 'b r;
	}
	};
	return Err(MirEvalError::Panic(format!("Overflow in {op:?}")));
	};
	Owned(r.to_le_bytes()[..lc.len()].to_vec())
	}
	BinOp::Offset => not_supported!("offset binop"),

(which causes the shift on the u128 that is used by the definition to carry the sign)

[UseK]

rust-analyzer version: rust-analyzer version: 0.4.2243-standalone (6725e04 2025-01-04)

I found this issue is fixed in the Pre-Release Version of rust-analyzer extension in VSCode.

Thanks! I love rust-analyzer!