Disable guessing 'other' cid; this prevents an issue in range analysis. It is not clear if guessing…

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index 09859de4d156b6aa43e87b52ab72f8862ad4423b..c8378b7923536f01bb51c5d50f74ca18c6966911 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -27,6 +27,11 @@ namespace dart {
 
 DEFINE_FLAG(int, getter_setter_ratio, 13,
     "Ratio of getter/setter usage used for double field unboxing heuristics");
+// Setting 'guess_other_cid' to true causes issue 23693 crash.
+// TODO(srdjan): Evaluate if that optimization is wrong.
+DEFINE_FLAG(bool, guess_other_cid, false,
+    "Artificially create type feedback for arithmetic etc. operations"
+    " by guessing the other unknown argument cid");
 DEFINE_FLAG(bool, load_cse, true, "Use redundant load elimination.");
 DEFINE_FLAG(bool, dead_store_elimination, true, "Eliminate dead stores");
 DEFINE_FLAG(int, max_polymorphic_checks, 4,
@@ -196,7 +201,9 @@ bool FlowGraphOptimizer::TryCreateICData(InstanceCallInstr* call) {
       Token::IsBinaryOperator(op_kind)) {
     // Guess cid: if one of the inputs is a number assume that the other
     // is a number of same type.
-    if (Compiler::guess_other_cid()) {
+    // Issue 23693. It is potentially wrong to assign types here that may
+    // conflict with other graph analysis.
+    if (FLAG_guess_other_cid) {
       const intptr_t cid_0 = class_ids[0];
       const intptr_t cid_1 = class_ids[1];
       if ((cid_0 == kDynamicCid) && (IsNumberCid(cid_1))) {