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_ast::ast::{IntTy, UintTy};
   7 use rustc_hir::{Item, ItemKind};
   8 use rustc_lint::{LateContext, LateLintPass};
   9 use rustc_middle::ty;
  10 use rustc_middle::ty::util::IntTypeExt;
  11 use rustc_session::{declare_lint_pass, declare_tool_lint};
  12 use std::convert::TryFrom;
  13
  14 declare_clippy_lint! {
  15     /// **What it does:** 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?** This will truncate the variant value on 32 bit
  19     /// architectures, but works fine on 64 bit.
  20     ///
  21     /// **Known problems:** None.
  22     ///
  23     /// **Example:**
  24     /// ```rust
  25     /// # #[cfg(target_pointer_width = "64")]
  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 declare_lint_pass!(UnportableVariant => [ENUM_CLIKE_UNPORTABLE_VARIANT]);
  38
  39 impl<'tcx> LateLintPass<'tcx> for UnportableVariant {
  40     #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
  41     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
  42         if cx.tcx.data_layout.pointer_size.bits() != 64 {
  43             return;
  44         }
  45         if let ItemKind::Enum(def, _) = &item.kind {
  46             for var in def.variants {
  47                 if let Some(anon_const) = &var.disr_expr {
  48                     let def_id = cx.tcx.hir().body_owner_def_id(anon_const.body);
  49                     let mut ty = cx.tcx.type_of(def_id.to_def_id());
  50                     let constant = cx
  51                         .tcx
  52                         .const_eval_poly(def_id.to_def_id())
  53                         .ok()
  54                         .map(|val| rustc_middle::ty::Const::from_value(cx.tcx, val, ty));
  55                     if let Some(Constant::Int(val)) = constant.and_then(miri_to_const) {
  56                         if let ty::Adt(adt, _) = ty.kind() {
  57                             if adt.is_enum() {
  58                                 ty = adt.repr.discr_type().to_ty(cx.tcx);
  59                             }
  60                         }
  61                         match ty.kind() {
  62                             ty::Int(IntTy::Isize) => {
  63                                 let val = ((val as i128) << 64) >> 64;
  64                                 if i32::try_from(val).is_ok() {
  65                                     continue;
  66                                 }
  67                             },
  68                             ty::Uint(UintTy::Usize) if val > u128::from(u32::MAX) => {},
  69                             _ => continue,
  70                         }
  71                         span_lint(
  72                             cx,
  73                             ENUM_CLIKE_UNPORTABLE_VARIANT,
  74                             var.span,
  75                             "C-like enum variant discriminant is not portable to 32-bit targets",
  76                         );
  77                     };
  78                 }
  79             }
  80         }
  81     }
  82 }