src/tools/clippy/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 clippy_utils::consts::{miri_to_const, Constant};
   5 use clippy_utils::diagnostics::span_lint;
   6 use rustc_hir::{Item, ItemKind};
   7 use rustc_lint::{LateContext, LateLintPass};
   8 use rustc_middle::ty::util::IntTypeExt;
   9 use rustc_middle::ty::{self, IntTy, UintTy};
  10 use rustc_session::{declare_lint_pass, declare_tool_lint};
  11 use std::convert::TryFrom;
  12
  13 declare_clippy_lint! {
  14     /// ### What it does
  15     /// Checks for C-like enumerations that are
  16     /// `repr(isize/usize)` and have values that don't fit into an `i32`.
  17     ///
  18     /// ### Why is this bad?
  19     /// This will truncate the variant value on 32 bit
  20     /// architectures, but works fine on 64 bit.
  21     ///
  22     /// ### Example
  23     /// ```rust
  24     /// # #[cfg(target_pointer_width = "64")]
  25     /// #[repr(usize)]
  26     /// enum NonPortable {
  27     ///     X = 0x1_0000_0000,
  28     ///     Y = 0,
  29     /// }
  30     /// ```
  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 declare_lint_pass!(UnportableVariant => [ENUM_CLIKE_UNPORTABLE_VARIANT]);
  37
  38 impl<'tcx> LateLintPass<'tcx> for UnportableVariant {
  39     #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
  40     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
  41         if cx.tcx.data_layout.pointer_size.bits() != 64 {
  42             return;
  43         }
  44         if let ItemKind::Enum(def, _) = &item.kind {
  45             for var in def.variants {
  46                 if let Some(anon_const) = &var.disr_expr {
  47                     let def_id = cx.tcx.hir().body_owner_def_id(anon_const.body);
  48                     let mut ty = cx.tcx.type_of(def_id.to_def_id());
  49                     let constant = cx
  50                         .tcx
  51                         .const_eval_poly(def_id.to_def_id())
  52                         .ok()
  53                         .map(|val| rustc_middle::ty::Const::from_value(cx.tcx, val, ty));
  54                     if let Some(Constant::Int(val)) = constant.and_then(miri_to_const) {
  55                         if let ty::Adt(adt, _) = ty.kind() {
  56                             if adt.is_enum() {
  57                                 ty = adt.repr.discr_type().to_ty(cx.tcx);
  58                             }
  59                         }
  60                         match ty.kind() {
  61                             ty::Int(IntTy::Isize) => {
  62                                 let val = ((val as i128) << 64) >> 64;
  63                                 if i32::try_from(val).is_ok() {
  64                                     continue;
  65                                 }
  66                             },
  67                             ty::Uint(UintTy::Usize) if val > u128::from(u32::MAX) => {},
  68                             _ => continue,
  69                         }
  70                         span_lint(
  71                             cx,
  72                             ENUM_CLIKE_UNPORTABLE_VARIANT,
  73                             var.span,
  74                             "C-like enum variant discriminant is not portable to 32-bit targets",
  75                         );
  76                     };
  77                 }
  78             }
  79         }
  80     }
  81 }