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 crate::consts::{miri_to_const, Constant};
   5 use crate::utils::span_lint;
   6 use rustc::hir::*;
   7 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   8 use rustc::mir::interpret::GlobalId;
   9 use rustc::ty;
  10 use rustc::ty::subst::InternalSubsts;
  11 use rustc::ty::util::IntTypeExt;
  12 use rustc::{declare_tool_lint, lint_array};
  13 use syntax::ast::{IntTy, UintTy};
  14
  15 declare_clippy_lint! {
  16     /// **What it does:** Checks for C-like enumerations that are
  17     /// `repr(isize/usize)` and have values that don't fit into an `i32`.
  18     ///
  19     /// **Why is this bad?** This will truncate the variant value on 32 bit
  20     /// architectures, but works fine on 64 bit.
  21     ///
  22     /// **Known problems:** None.
  23     ///
  24     /// **Example:**
  25     /// ```rust
  26     /// #[repr(usize)]
  27     /// enum NonPortable {
  28     ///     X = 0x1_0000_0000,
  29     ///     Y = 0,
  30     /// }
  31     /// ```
  32     pub ENUM_CLIKE_UNPORTABLE_VARIANT,
  33     correctness,
  34     "C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`"
  35 }
  36
  37 pub struct UnportableVariant;
  38
  39 impl LintPass for UnportableVariant {
  40     fn get_lints(&self) -> LintArray {
  41         lint_array!(ENUM_CLIKE_UNPORTABLE_VARIANT)
  42     }
  43
  44     fn name(&self) -> &'static str {
  45         "UnportableVariant"
  46     }
  47 }
  48
  49 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnportableVariant {
  50     #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
  51     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
  52         if cx.tcx.data_layout.pointer_size.bits() != 64 {
  53             return;
  54         }
  55         if let ItemKind::Enum(ref def, _) = item.node {
  56             for var in &def.variants {
  57                 let variant = &var.node;
  58                 if let Some(ref anon_const) = variant.disr_expr {
  59                     let param_env = ty::ParamEnv::empty();
  60                     let def_id = cx.tcx.hir().body_owner_def_id(anon_const.body);
  61                     let substs = InternalSubsts::identity_for_item(cx.tcx.global_tcx(), def_id);
  62                     let instance = ty::Instance::new(def_id, substs);
  63                     let c_id = GlobalId {
  64                         instance,
  65                         promoted: None,
  66                     };
  67                     let constant = cx.tcx.const_eval(param_env.and(c_id)).ok();
  68                     if let Some(Constant::Int(val)) = constant.and_then(|c| miri_to_const(cx.tcx, &c)) {
  69                         let mut ty = cx.tcx.type_of(def_id);
  70                         if let ty::Adt(adt, _) = ty.sty {
  71                             if adt.is_enum() {
  72                                 ty = adt.repr.discr_type().to_ty(cx.tcx);
  73                             }
  74                         }
  75                         match ty.sty {
  76                             ty::Int(IntTy::Isize) => {
  77                                 let val = ((val as i128) << 64) >> 64;
  78                                 if val <= i128::from(i32::max_value()) && val >= i128::from(i32::min_value()) {
  79                                     continue;
  80                                 }
  81                             },
  82                             ty::Uint(UintTy::Usize) if val > u128::from(u32::max_value()) => {},
  83                             _ => continue,
  84                         }
  85                         span_lint(
  86                             cx,
  87                             ENUM_CLIKE_UNPORTABLE_VARIANT,
  88                             var.span,
  89                             "Clike enum variant discriminant is not portable to 32-bit targets",
  90                         );
  91                     };
  92                 }
  93             }
  94         }
  95     }
  96 }