src/tools/clippy/clippy_lints/src/transmute/utils.rs

   1 use rustc_hir as hir;
   2 use rustc_hir::Expr;
   3 use rustc_hir_typeck::{cast, FnCtxt, Inherited};
   4 use rustc_lint::LateContext;
   5 use rustc_middle::ty::{cast::CastKind, Ty};
   6 use rustc_span::DUMMY_SP;
   7
   8 // check if the component types of the transmuted collection and the result have different ABI,
   9 // size or alignment
  10 pub(super) fn is_layout_incompatible<'tcx>(cx: &LateContext<'tcx>, from: Ty<'tcx>, to: Ty<'tcx>) -> bool {
  11     if let Ok(from) = cx.tcx.try_normalize_erasing_regions(cx.param_env, from)
  12         && let Ok(to) = cx.tcx.try_normalize_erasing_regions(cx.param_env, to)
  13         && let Ok(from_layout) = cx.tcx.layout_of(cx.param_env.and(from))
  14         && let Ok(to_layout) = cx.tcx.layout_of(cx.param_env.and(to))
  15     {
  16         from_layout.size != to_layout.size || from_layout.align.abi != to_layout.align.abi
  17     } else {
  18         // no idea about layout, so don't lint
  19         false
  20     }
  21 }
  22
  23 /// If a cast from `from_ty` to `to_ty` is valid, returns an Ok containing the kind of
  24 /// the cast. In certain cases, including some invalid casts from array references
  25 /// to pointers, this may cause additional errors to be emitted and/or ICE error
  26 /// messages. This function will panic if that occurs.
  27 pub(super) fn check_cast<'tcx>(
  28     cx: &LateContext<'tcx>,
  29     e: &'tcx Expr<'_>,
  30     from_ty: Ty<'tcx>,
  31     to_ty: Ty<'tcx>,
  32 ) -> Option<CastKind> {
  33     let hir_id = e.hir_id;
  34     let local_def_id = hir_id.owner.def_id;
  35
  36     Inherited::build(cx.tcx, local_def_id).enter(|inherited| {
  37         let fn_ctxt = FnCtxt::new(inherited, cx.param_env, local_def_id);
  38
  39         // If we already have errors, we can't be sure we can pointer cast.
  40         assert!(
  41             !fn_ctxt.errors_reported_since_creation(),
  42             "Newly created FnCtxt contained errors"
  43         );
  44
  45         if let Ok(check) = cast::CastCheck::new(
  46             &fn_ctxt,
  47             e,
  48             from_ty,
  49             to_ty,
  50             // We won't show any error to the user, so we don't care what the span is here.
  51             DUMMY_SP,
  52             DUMMY_SP,
  53             hir::Constness::NotConst,
  54         ) {
  55             let res = check.do_check(&fn_ctxt);
  56
  57             // do_check's documentation says that it might return Ok and create
  58             // errors in the fcx instead of returning Err in some cases. Those cases
  59             // should be filtered out before getting here.
  60             assert!(
  61                 !fn_ctxt.errors_reported_since_creation(),
  62                 "`fn_ctxt` contained errors after cast check!"
  63             );
  64
  65             res.ok()
  66         } else {
  67             None
  68         }
  69     })
  70 }