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::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   5 use crate::rustc::{declare_tool_lint, lint_array};
   6 use crate::rustc::hir::*;
   7 use crate::rustc::ty;
   8 use crate::rustc::ty::subst::Substs;
   9 use crate::syntax::ast::{IntTy, UintTy};
  10 use crate::utils::span_lint;
  11 use crate::consts::{Constant, miri_to_const};
  12 use crate::rustc::ty::util::IntTypeExt;
  13 use crate::rustc::mir::interpret::GlobalId;
  14
  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 /// #[repr(usize)]
  26 /// enum NonPortable {
  27 ///     X = 0x1_0000_0000,
  28 ///     Y = 0
  29 /// }
  30 /// ```
  31 declare_clippy_lint! {
  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
  45 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnportableVariant {
  46     #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
  47     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
  48         if cx.tcx.data_layout.pointer_size.bits() != 64 {
  49             return;
  50         }
  51         if let ItemKind::Enum(ref def, _) = item.node {
  52             for var in &def.variants {
  53                 let variant = &var.node;
  54                 if let Some(ref anon_const) = variant.disr_expr {
  55                     let param_env = ty::ParamEnv::empty();
  56                     let did = cx.tcx.hir.body_owner_def_id(anon_const.body);
  57                     let substs = Substs::identity_for_item(cx.tcx.global_tcx(), did);
  58                     let instance = ty::Instance::new(did, substs);
  59                     let cid = GlobalId {
  60                         instance,
  61                         promoted: None
  62                     };
  63                     let constant = cx.tcx.const_eval(param_env.and(cid)).ok();
  64                     if let Some(Constant::Int(val)) = constant.and_then(|c| miri_to_const(cx.tcx, c)) {
  65                         let mut ty = cx.tcx.type_of(did);
  66                         if let ty::Adt(adt, _) = ty.sty {
  67                             if adt.is_enum() {
  68                                 ty = adt.repr.discr_type().to_ty(cx.tcx);
  69                             }
  70                         }
  71                         match ty.sty {
  72                             ty::Int(IntTy::Isize) => {
  73                                 let val = ((val as i128) << 64) >> 64;
  74                                 if val <= i128::from(i32::max_value()) && val >= i128::from(i32::min_value()) {
  75                                     continue;
  76                                 }
  77                             }
  78                             ty::Uint(UintTy::Usize) if val > u128::from(u32::max_value()) => {},
  79                             _ => continue,
  80                         }
  81                         span_lint(
  82                             cx,
  83                             ENUM_CLIKE_UNPORTABLE_VARIANT,
  84                             var.span,
  85                             "Clike enum variant discriminant is not portable to 32-bit targets",
  86                         );
  87                     };
  88                 }
  89             }
  90         }
  91     }
  92 }