clippy_lints/src/enum_clike.rs

   1 //! lint on C-like enums that are `repr(isize/usize)` and have values that
   2 //! don't fit into an `i32`
   3
   4 use rustc::lint::*;
   5 use rustc::hir::*;
   6 use rustc::ty;
   7 use rustc::ty::subst::Substs;
   8 use syntax::ast::{IntTy, UintTy};
   9 use crate::utils::span_lint;
  10 use crate::consts::{Constant, miri_to_const};
  11 use rustc::ty::util::IntTypeExt;
  12 use rustc::mir::interpret::GlobalId;
  13
  14 /// **What it does:** Checks for C-like enumerations that are
  15 /// `repr(isize/usize)` and have values that don't fit into an `i32`.
  16 ///
  17 /// **Why is this bad?** This will truncate the variant value on 32 bit
  18 /// architectures, but works fine on 64 bit.
  19 ///
  20 /// **Known problems:** None.
  21 ///
  22 /// **Example:**
  23 /// ```rust
  24 /// #[repr(usize)]
  25 /// enum NonPortable {
  26 ///     X = 0x1_0000_0000,
  27 ///     Y = 0
  28 /// }
  29 /// ```
  30 declare_clippy_lint! {
  31     pub ENUM_CLIKE_UNPORTABLE_VARIANT,
  32     correctness,
  33     "C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`"
  34 }
  35
  36 pub struct UnportableVariant;
  37
  38 impl LintPass for UnportableVariant {
  39     fn get_lints(&self) -> LintArray {
  40         lint_array!(ENUM_CLIKE_UNPORTABLE_VARIANT)
  41     }
  42 }
  43
  44 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnportableVariant {
  45     #[allow(cast_possible_truncation, cast_sign_loss)]
  46     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
  47         if cx.tcx.data_layout.pointer_size.bits() != 64 {
  48             return;
  49         }
  50         if let ItemEnum(ref def, _) = item.node {
  51             for var in &def.variants {
  52                 let variant = &var.node;
  53                 if let Some(ref anon_const) = variant.disr_expr {
  54                     let param_env = ty::ParamEnv::empty();
  55                     let did = cx.tcx.hir.body_owner_def_id(anon_const.body);
  56                     let substs = Substs::identity_for_item(cx.tcx.global_tcx(), did);
  57                     let instance = ty::Instance::new(did, substs);
  58                     let cid = GlobalId {
  59                         instance,
  60                         promoted: None
  61                     };
  62                     let constant = cx.tcx.const_eval(param_env.and(cid)).ok();
  63                     if let Some(Constant::Int(val)) = constant.and_then(|c| miri_to_const(cx.tcx, c)) {
  64                         let mut ty = cx.tcx.type_of(did);
  65                         if let ty::TyAdt(adt, _) = ty.sty {
  66                             if adt.is_enum() {
  67                                 ty = adt.repr.discr_type().to_ty(cx.tcx);
  68                             }
  69                         }
  70                         match ty.sty {
  71                             ty::TyInt(IntTy::Isize) => {
  72                                 let val = ((val as i128) << 64) >> 64;
  73                                 if val <= i128::from(i32::max_value()) && val >= i128::from(i32::min_value()) {
  74                                     continue;
  75                                 }
  76                             }
  77                             ty::TyUint(UintTy::Usize) if val > u128::from(u32::max_value()) => {},
  78                             _ => continue,
  79                         }
  80                         span_lint(
  81                             cx,
  82                             ENUM_CLIKE_UNPORTABLE_VARIANT,
  83                             var.span,
  84                             "Clike enum variant discriminant is not portable to 32-bit targets",
  85                         );
  86                     };
  87                 }
  88             }
  89         }
  90     }
  91 }