rust-lang · bors · Jun 19, 2020 · May 23, 2020 · May 23, 2020 · May 30, 2020
diff --git a/src/librustc_session/lint/builtin.rs b/src/librustc_session/lint/builtin.rs
@@ -534,6  534,16 @@ declare_lint! {
     @feature_gate = sym::unsafe_block_in_unsafe_fn;
 }
 
 declare_lint! {
     pub CENUM_IMPL_DROP_CAST,
     Warn,
     "a C-like enum implementing Drop is cast",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #73333 <https://github.com/rust-lang/rust/issues/73333>",
         edition: None,
     };
 }
 
 declare_lint_pass! {
     /// Does nothing as a lint pass, but registers some `Lint`s
     /// that are used by other parts of the compiler.
@@ -607,6  617,7 @@ declare_lint_pass! {
         ASM_SUB_REGISTER,
         UNSAFE_OP_IN_UNSAFE_FN,
         INCOMPLETE_INCLUDE,
         CENUM_IMPL_DROP_CAST,
     ]
 }
 

diff --git a/src/librustc_typeck/check/cast.rs b/src/librustc_typeck/check/cast.rs
@@ -678,7  678,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             (FnPtr, Ptr(mt)) => self.check_fptr_ptr_cast(fcx, mt),
 
             // prim -> prim
-            (Int(CEnum), Int(_)) => Ok(CastKind::EnumCast),
             (Int(CEnum), Int(_)) => {
                 self.cenum_impl_drop_lint(fcx);
                 Ok(CastKind::EnumCast)
             }
             (Int(Char) | Int(Bool), Int(_)) => Ok(CastKind::PrimIntCast),
 
             (Int(_) | Float, Int(_) | Float) => Ok(CastKind::NumericCast),
@@ -775,11  778,13 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                 // Coerce to a raw pointer so that we generate AddressOf in MIR.
                 let array_ptr_type = fcx.tcx.mk_ptr(m_expr);
                 fcx.try_coerce(self.expr, self.expr_ty, array_ptr_type, AllowTwoPhase::No)
-                    .unwrap_or_else(|_| bug!(
                     .unwrap_or_else(|_| {
                         bug!(
                         "could not cast from reference to array to pointer to array ({:?} to {:?})",
                         self.expr_ty,
                         array_ptr_type,
-                    ));
                     )
                     });
 
                 // this will report a type mismatch if needed
                 fcx.demand_eqtype(self.span, ety, m_cast.ty);
@@ -809,6  814,25 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             Err(err) => Err(err),
         }
     }
 
     fn cenum_impl_drop_lint(&self, fcx: &FnCtxt<'a, 'tcx>) {
         if let ty::Adt(d, _) = self.expr_ty.kind {
             if d.has_dtor(fcx.tcx) {
                 fcx.tcx.struct_span_lint_hir(
                     lint::builtin::CENUM_IMPL_DROP_CAST,
                     self.expr.hir_id,
                     self.span,
                     |err| {
                         err.build(&format!(
                             "cannot cast enum `{}` into integer `{}` because it implements `Drop`",
                             self.expr_ty, self.cast_ty
                         ))
                         .emit();
                     },
                 );
             }
         }
     }
 }
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

diff --git a/src/test/ui/cenum_impl_drop_cast.rs b/src/test/ui/cenum_impl_drop_cast.rs
@@ -0,0  1,18 @@
 #![deny(cenum_impl_drop_cast)]
 
 enum E {
     A = 0,
 }
 
 impl Drop for E {
     fn drop(&mut self) {
         println!("Drop");
     }
 }
 
 fn main() {
     let e = E::A;
     let i = e as u32;
     //~^ ERROR cannot cast enum `E` into integer `u32` because it implements `Drop`
     //~| WARN this was previously accepted
 }
diff --git a/src/test/ui/cenum_impl_drop_cast.stderr b/src/test/ui/cenum_impl_drop_cast.stderr
@@ -0,0  1,16 @@
 error: cannot cast enum `E` into integer `u32` because it implements `Drop`
   --> $DIR/cenum_impl_drop_cast.rs:15:13
    |
 LL |     let i = e as u32;
    |             ^^^^^^^^
    |
 note: the lint level is defined here
   --> $DIR/cenum_impl_drop_cast.rs:1:9
    |
 LL | #![deny(cenum_impl_drop_cast)]
    |         ^^^^^^^^^^^^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #73333 <https://github.com/rust-lang/rust/issues/73333>
 
 error: aborting due to previous error