rust/clippy_lints/src/enum_clike.rs

64 lines
2.1 KiB
Rust

//! lint on C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`
use rustc::lint::*;
use rustc::middle::const_val::ConstVal;
use rustc_const_math::*;
use rustc::hir::*;
use utils::span_lint;
/// **What it does:** Checks for C-like enumerations that are
/// `repr(isize/usize)` and have values that don't fit into an `i32`.
///
/// **Why is this bad?** This will truncate the variant value on 32 bit
/// architectures, but works fine on 64 bit.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// #[repr(usize)]
/// enum NonPortable {
/// X = 0x1_0000_0000,
/// Y = 0
/// }
/// ```
declare_lint! {
pub ENUM_CLIKE_UNPORTABLE_VARIANT,
Warn,
"C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`"
}
pub struct UnportableVariant;
impl LintPass for UnportableVariant {
fn get_lints(&self) -> LintArray {
lint_array!(ENUM_CLIKE_UNPORTABLE_VARIANT)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnportableVariant {
#[allow(cast_possible_truncation, cast_sign_loss)]
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
if let ItemEnum(ref def, _) = item.node {
for var in &def.variants {
let variant = &var.node;
if let Some(body_id) = variant.disr_expr {
use rustc_const_eval::*;
let constcx = ConstContext::with_tables(cx.tcx, cx.tcx.body_tables(body_id));
let bad = match constcx.eval(&cx.tcx.hir.body(body_id).value) {
Ok(ConstVal::Integral(Usize(Us64(i)))) => i as u32 as u64 != i,
Ok(ConstVal::Integral(Isize(Is64(i)))) => i as i32 as i64 != i,
_ => false,
};
if bad {
span_lint(cx,
ENUM_CLIKE_UNPORTABLE_VARIANT,
var.span,
"Clike enum variant discriminant is not portable to 32-bit targets");
}
}
}
}
}
}