clippy_lints/src/enum_clike.rs

   1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution.
   3 //
   4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   7 // option. This file may not be copied, modified, or distributed
   8 // except according to those terms.
   9
  10
  11 //! lint on C-like enums that are `repr(isize/usize)` and have values that
  12 //! don't fit into an `i32`
  13
  14 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
  15 use crate::rustc::{declare_tool_lint, lint_array};
  16 use crate::rustc::hir::*;
  17 use crate::rustc::ty;
  18 use crate::rustc::ty::subst::Substs;
  19 use crate::syntax::ast::{IntTy, UintTy};
  20 use crate::utils::span_lint;
  21 use crate::consts::{Constant, miri_to_const};
  22 use crate::rustc::ty::util::IntTypeExt;
  23 use crate::rustc::mir::interpret::GlobalId;
  24
  25 /// **What it does:** Checks for C-like enumerations that are
  26 /// `repr(isize/usize)` and have values that don't fit into an `i32`.
  27 ///
  28 /// **Why is this bad?** This will truncate the variant value on 32 bit
  29 /// architectures, but works fine on 64 bit.
  30 ///
  31 /// **Known problems:** None.
  32 ///
  33 /// **Example:**
  34 /// ```rust
  35 /// #[repr(usize)]
  36 /// enum NonPortable {
  37 ///     X = 0x1_0000_0000,
  38 ///     Y = 0
  39 /// }
  40 /// ```
  41 declare_clippy_lint! {
  42     pub ENUM_CLIKE_UNPORTABLE_VARIANT,
  43     correctness,
  44     "C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`"
  45 }
  46
  47 pub struct UnportableVariant;
  48
  49 impl LintPass for UnportableVariant {
  50     fn get_lints(&self) -> LintArray {
  51         lint_array!(ENUM_CLIKE_UNPORTABLE_VARIANT)
  52     }
  53 }
  54
  55 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnportableVariant {
  56     #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
  57     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
  58         if cx.tcx.data_layout.pointer_size.bits() != 64 {
  59             return;
  60         }
  61         if let ItemKind::Enum(ref def, _) = item.node {
  62             for var in &def.variants {
  63                 let variant = &var.node;
  64                 if let Some(ref anon_const) = variant.disr_expr {
  65                     let param_env = ty::ParamEnv::empty();
  66                     let def_id = cx.tcx.hir.body_owner_def_id(anon_const.body);
  67                     let substs = Substs::identity_for_item(cx.tcx.global_tcx(), def_id);
  68                     let instance = ty::Instance::new(def_id, substs);
  69                     let c_id = GlobalId {
  70                         instance,
  71                         promoted: None
  72                     };
  73                     let constant = cx.tcx.const_eval(param_env.and(c_id)).ok();
  74                     if let Some(Constant::Int(val)) = constant.and_then(|c| miri_to_const(cx.tcx, c)) {
  75                         let mut ty = cx.tcx.type_of(def_id);
  76                         if let ty::Adt(adt, _) = ty.sty {
  77                             if adt.is_enum() {
  78                                 ty = adt.repr.discr_type().to_ty(cx.tcx);
  79                             }
  80                         }
  81                         match ty.sty {
  82                             ty::Int(IntTy::Isize) => {
  83                                 let val = ((val as i128) << 64) >> 64;
  84                                 if val <= i128::from(i32::max_value()) && val >= i128::from(i32::min_value()) {
  85                                     continue;
  86                                 }
  87                             }
  88                             ty::Uint(UintTy::Usize) if val > u128::from(u32::max_value()) => {},
  89                             _ => continue,
  90                         }
  91                         span_lint(
  92                             cx,
  93                             ENUM_CLIKE_UNPORTABLE_VARIANT,
  94                             var.span,
  95                             "Clike enum variant discriminant is not portable to 32-bit targets",
  96                         );
  97                     };
  98                 }
  99             }
 100         }
 101     }
 102 }