Rollup merge of #66790 - christianpoveda:check-set-discriminant, r=oli-obk

Do `min_const_fn` checks for `SetDiscriminant`s target

Fixes https://github.com/rust-lang/rust/issues/66556

r? @oli-obk @ecstatic-morse

src/librustc_mir/transform/check_consts/validation.rs

@@ -560,7 +560,7 @@ fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
         trace!("visit_statement: statement={:?} location={:?}", statement, location);
 
         match statement.kind {
-            StatementKind::Assign(..) => {
+            StatementKind::Assign(..) | StatementKind::SetDiscriminant { .. } => {
                 self.super_statement(statement, location);
             }
             StatementKind::FakeRead(FakeReadCause::ForMatchedPlace, _) => {
@@ -568,7 +568,6 @@ fn visit_statement(&mut self, statement: &Statement<'tcx>, location: 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()))