Check SetDiscriminant place

Author: pvdrz

src/librustc_mir/transform/check_consts/validation.rs

@@ -566,9 +566,12 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
             StatementKind::FakeRead(FakeReadCause::ForMatchedPlace, _) => {
                 self.check_op(ops::IfOrMatch);
             }
+            StatementKind::SetDiscriminant { ref place, .. } => {
+                let ctx = PlaceContext::MutatingUse(MutatingUseContext::Projection);
+                self.visit_place(&place, ctx, location)
+            }
             // FIXME(eddyb) should these really do nothing?
             StatementKind::FakeRead(..) |
-            StatementKind::SetDiscriminant { .. } |
             StatementKind::StorageLive(_) |
             StatementKind::StorageDead(_) |
             StatementKind::InlineAsm {..} |

src/librustc_mir/transform/qualify_min_const_fn.rs

@@ -225,7 +225,7 @@ fn check_statement(
         StatementKind::FakeRead(_, place) => check_place(tcx, place, span, def_id, body),
 
         // just an assignment
-        StatementKind::SetDiscriminant { .. } => Ok(()),
+        StatementKind::SetDiscriminant { place, .. } => check_place(tcx, place, span, def_id, body),
 
         | StatementKind::InlineAsm { .. } => {
             Err((span, "cannot use inline assembly in const fn".into()))