Grammar causes freeze on on long chain of ternary operators

Original issue filed by @nblog in https://github.com/microsoft/vscode/issues/87225
## Details

What editor are you seeing the problem in? (e.g. Atom, Visual Studio Code, etc.)
VS Code
What version of the editor are you using?
1.42 Insiders
What color theme are you using?
not applicable

## Repro
```csharp
CallEvent callEvent = new CallEvent(traceId, (ulong)((callNumber == 0UL) ? ((long)r["CallNumber"]) : ((long)callNumber)), (ulong)((long)r["Peer"]), (int)((long)r["Priority"]), (string)((obj2 == DBNull.Value) ? string.Empty : obj2), (EventFlags)((long)r["EventFlags"]), (ulong)((long)r["RetValue"]), (string)((obj3 == DBNull.Value) ? string.Empty : obj3), (string)((obj4 == DBNull.Value) ? string.Empty : obj4), (HookType)((long)r["HookType"]), (uint)((long)r["ChainDepth"]), (uint)((long)r["Cookie"]), (double)r["Time"], (double)r["GenerationTime"], (int)((long)r["ParamMainIndex"]), (uint)((long)r["Pid"]), (uint)((long)r["Tid"]), (string)((obj5 == DBNull.Value) ? string.Empty : obj5), (string)((obj6 == DBNull.Value) ? string.Empty : obj6), (string)((obj7 == DBNull.Value) ? string.Empty : obj7), (bool)r["Success"], ancestors);
```
This line cause the freeze.