Assert on invalid IR

Author: SingleAccretion

src/coreclr/jit/earlyprop.cpp

@@ -388,6 +388,13 @@ GenTree* Compiler::optEarlyPropRewriteTree(GenTree* tree, LocalNumberToNullCheck
                     if ((checkConstVal >= 0) && (checkConstVal < actualConstVal))
                     {
                         GenTree* comma = check->gtGetParent(nullptr);
+
+                        // We should never see cases other than these in the IR,
+                        // as the check node does not produce a value.
+                        assert(((comma != nullptr) && comma->OperIs(GT_COMMA) && (comma->gtGetOp1() == check)) ||
+                               (check == compCurStmt->GetRootNode()));
+
+                        // Still, we guard here so that release builds do not try to optimize trees we don't understand.
                         if (((comma != nullptr) && comma->OperIs(GT_COMMA) && (comma->gtGetOp1() == check)) ||
                             (check == compCurStmt->GetRootNode()))
                         {