Fix dynamic assembly load logic in Tracer

src/Simulation/EntryPointDriver/Simulation.cs

@@ -38,8 +38,10 @@ internal static async Task<int> Simulate(
                 var coreAssemblyName = 
                     (from aName in entryPoint.GetType().Assembly.GetReferencedAssemblies()
                     where aName.Name == "Microsoft.Quantum.QSharp.Core"
-                    select aName).First();
-                var coreAssembly = Assembly.Load(coreAssemblyName.FullName);
+                    select aName).FirstOrDefault();
+                var coreAssembly = coreAssemblyName != null ? 
+                    Assembly.Load(coreAssemblyName.FullName) :
+                    null;
 
                 var resourcesEstimator = new ResourcesEstimator(coreAssembly);
                 await resourcesEstimator.Run<TCallable, TIn, TOut>(entryPoint.CreateArgument(parseResult));

src/Simulation/Simulators/QCTraceSimulator/QCTraceSimulatorImpl.cs

@@ -152,41 +152,43 @@ private void RegisterPrimitiveOperationsGivenAsCircuits(Assembly? coreAssembly)
             var intrinsicAssembly = coreAssembly;
             if (intrinsicAssembly == null)
             {
-                intrinsicAssembly = 
-                    (from assembly in AppDomain.CurrentDomain.GetAssemblies()
-                    where assembly.GetType("Microsoft.Quantum.Intrinsic.X") != null
-                    select assembly).First();
+                var currentName = this.GetType().Assembly.GetName();
+                var coreName = currentName.FullName.Replace("Simulators", "QSharp.Core");
+                try
+                {
+                    intrinsicAssembly = AppDomain.CurrentDomain.Load(coreName);
+                }
+                catch { }
             }
-            IEnumerable<Type> primitiveOperationTypes =
-                from op in intrinsicAssembly.GetExportedTypes()
-                where op.IsSubclassOf(typeof(AbstractCallable))
-                select op;
 
-            if (primitiveOperationTypes.Count() == 0)
+            if (intrinsicAssembly != null)
             {
-                throw new Exception("Unable to load intrinsic types. The ResourcesEstimator can only be used with the default execution target.");
-            }
-
-            IEnumerable<Type> primitiveOperationAsCircuits =
-                from op in typeof(Circuits.X).Assembly.GetExportedTypes()
-                where op.IsSubclassOf(typeof(AbstractCallable))
-                      && op.Namespace == typeof(Circuits.X).Namespace
-                select op;
+                IEnumerable<Type> primitiveOperationTypes =
+                    from op in intrinsicAssembly.GetExportedTypes()
+                    where op.IsSubclassOf(typeof(AbstractCallable))
+                    select op;
 
-            foreach (Type operationType in primitiveOperationTypes)
-            {
-                IEnumerable<Type> machingCircuitTypes =
-                    from op in primitiveOperationAsCircuits
-                    where op.Name == operationType.Name
+                IEnumerable<Type> primitiveOperationAsCircuits =
+                    from op in typeof(Circuits.X).Assembly.GetExportedTypes()
+                    where op.IsSubclassOf(typeof(AbstractCallable))
+                        && op.Namespace == typeof(Circuits.X).Namespace
                     select op;
 
-                int numberOfMatchesFound = machingCircuitTypes.Count();
-                Debug.Assert(
-                     numberOfMatchesFound <= 1,
-                    "There should be at most one matching operation.");
-                if (numberOfMatchesFound == 1)
+                foreach (Type operationType in primitiveOperationTypes)
                 {
-                    Register(operationType, machingCircuitTypes.First(), operationType.ICallableType());
+                    IEnumerable<Type> machingCircuitTypes =
+                        from op in primitiveOperationAsCircuits
+                        where op.Name == operationType.Name
+                        select op;
+
+                    int numberOfMatchesFound = machingCircuitTypes.Count();
+                    Debug.Assert(
+                        numberOfMatchesFound <= 1,
+                        "There should be at most one matching operation.");
+                    if (numberOfMatchesFound == 1)
+                    {
+                        Register(operationType, machingCircuitTypes.First(), operationType.ICallableType());
+                    }
                 }
             }
         }

src/Simulation/Simulators/ResourcesEstimator/ResourcesEstimator.cs

@@ -48,7 +48,7 @@ public static QCTraceSimulatorConfiguration RecommendedConfig() =>
         /// Constructor used by entry point driver to provide the assembly for core types that
         /// need to be overriden.
         /// </summary>
-        public ResourcesEstimator(Assembly coreAssembly) : base(RecommendedConfig(), coreAssembly)
+        public ResourcesEstimator(Assembly? coreAssembly) : base(RecommendedConfig(), coreAssembly)
         {
         }