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