Merge pull request #350 from RalfJung/inhabited

get rid of ad-hoc inhabitedness test

src/librustc_mir/interpret/eval_context.rs

@@ -1818,7 +1818,7 @@ fn try_read_value(&self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<'tcx, Option<
                 let val = match val {
                     PrimVal::Bytes(0) => false,
                     PrimVal::Bytes(1) => true,
-                    // TODO: This seems a little overeager, should reading at bool type already be UB?
+                    // TODO: This seems a little overeager, should reading at bool type already be insta-UB?
                     _ => return err!(InvalidBool),
                 };
                 PrimVal::from_bool(val)
@@ -2237,10 +2237,6 @@ fn size(self) -> Size {
     }
 }
 
-pub fn is_inhabited<'a, 'tcx: 'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> bool {
-    ty.uninhabited_from(&mut HashMap::default(), tcx).is_empty()
-}
-
 /// FIXME: expose trans::monomorphize::resolve_closure
 pub fn resolve_closure<'a, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,

src/librustc_mir/interpret/terminator/mod.rs

@@ -251,9 +251,6 @@ fn eval_fn_call(
                     _ => return err!(Unreachable),
                 };
                 let ty = sig.output();
-                if !eval_context::is_inhabited(self.tcx, ty) {
-                    return err!(Unreachable);
-                }
                 let layout = self.type_layout(ty)?;
                 M::call_intrinsic(self, instance, args, ret, ty, layout, target)?;
                 self.dump_local(ret);

tests/compile-fail/never_say_never.rs

@@ -1,3 +1,6 @@
+// This should fail even without validation
+// compile-flags: -Zmir-emit-validate=0
+
 #![feature(never_type)]
 #![allow(unreachable_code)]
 

tests/compile-fail/never_transmute_humans.rs

@@ -1,3 +1,6 @@
+// This should fail even without validation
+// compile-flags: -Zmir-emit-validate=0
+
 #![feature(never_type)]
 #![allow(unreachable_code)]
 #![allow(unused_variables)]

tests/compile-fail/never_transmute_void.rs

@@ -1,3 +1,6 @@
+// This should fail even without validation
+// compile-flags: -Zmir-emit-validate=0
+
 #![feature(never_type)]
 #![allow(unreachable_code)]
 #![allow(unused_variables)]
@@ -5,12 +8,12 @@
 enum Void {}
 
 fn f(v: Void) -> ! {
-    match v {}
+    match v {} //~ ERROR entered unreachable code
 }
 
 fn main() {
     let v: Void = unsafe {
-        std::mem::transmute::<(), Void>(()) //~ ERROR entered unreachable code
+        std::mem::transmute::<(), Void>(())
     };
     f(v);
 }