src/tools/clippy/clippy_lints/src/casts/cast_possible_wrap.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use clippy_utils::ty::is_isize_or_usize;
   3 use rustc_hir::Expr;
   4 use rustc_lint::LateContext;
   5 use rustc_middle::ty::Ty;
   6
   7 use super::{utils, CAST_POSSIBLE_WRAP};
   8
   9 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
  10     if !(cast_from.is_integral() && cast_to.is_integral()) {
  11         return;
  12     }
  13
  14     let arch_64_suffix = " on targets with 64-bit wide pointers";
  15     let arch_32_suffix = " on targets with 32-bit wide pointers";
  16     let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
  17     let from_nbits = utils::int_ty_to_nbits(cast_from, cx.tcx);
  18     let to_nbits = utils::int_ty_to_nbits(cast_to, cx.tcx);
  19
  20     let (should_lint, suffix) = match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
  21         (true, true) | (false, false) => (to_nbits == from_nbits && cast_unsigned_to_signed, ""),
  22         (true, false) => (to_nbits <= 32 && cast_unsigned_to_signed, arch_32_suffix),
  23         (false, true) => (
  24             cast_unsigned_to_signed,
  25             if from_nbits == 64 {
  26                 arch_64_suffix
  27             } else {
  28                 arch_32_suffix
  29             },
  30         ),
  31     };
  32
  33     if should_lint {
  34         span_lint(
  35             cx,
  36             CAST_POSSIBLE_WRAP,
  37             expr.span,
  38             &format!(
  39                 "casting `{}` to `{}` may wrap around the value{}",
  40                 cast_from, cast_to, suffix,
  41             ),
  42         );
  43     }
  44 }