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