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//! lint on C-like enums that are `repr(isize/usize)` and have values that
//! don't fit into an `i32`
use crate::consts::{miri_to_const, Constant};
use crate::utils::span_lint;
use rustc::hir::*;
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::mir::interpret::GlobalId;
use rustc::ty;
use rustc::ty::subst::InternalSubsts;
use rustc::ty::util::IntTypeExt;
use rustc::{declare_tool_lint, lint_array};
use syntax::ast::{IntTy, UintTy};
/// **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_clippy_lint! {
pub ENUM_CLIKE_UNPORTABLE_VARIANT,
correctness,
"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)
}
fn name(&self) -> &'static str {
"UnportableVariant"
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnportableVariant {
#[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
if cx.tcx.data_layout.pointer_size.bits() != 64 {
return;
}
if let ItemKind::Enum(ref def, _) = item.node {
for var in &def.variants {
let variant = &var.node;
if let Some(ref anon_const) = variant.disr_expr {
let param_env = ty::ParamEnv::empty();
let def_id = cx.tcx.hir().body_owner_def_id(anon_const.body);
let substs = InternalSubsts::identity_for_item(cx.tcx.global_tcx(), def_id);
let instance = ty::Instance::new(def_id, substs);
let c_id = GlobalId {
instance,
promoted: None,
};
let constant = cx.tcx.const_eval(param_env.and(c_id)).ok();
if let Some(Constant::Int(val)) = constant.and_then(|c| miri_to_const(cx.tcx, &c)) {
let mut ty = cx.tcx.type_of(def_id);
if let ty::Adt(adt, _) = ty.sty {
if adt.is_enum() {
ty = adt.repr.discr_type().to_ty(cx.tcx);
}
}
match ty.sty {
ty::Int(IntTy::Isize) => {
let val = ((val as i128) << 64) >> 64;
if val <= i128::from(i32::max_value()) && val >= i128::from(i32::min_value()) {
continue;
}
},
ty::Uint(UintTy::Usize) if val > u128::from(u32::max_value()) => {},
_ => continue,
}
span_lint(
cx,
ENUM_CLIKE_UNPORTABLE_VARIANT,
var.span,
"Clike enum variant discriminant is not portable to 32-bit targets",
);
};
}
}
}
}
}
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