protected override void ImplementBody(ILProcessor il, FieldReference methodInfoField, FieldReference propertyInfoField, MethodReference proceed, MethodReference proceedTargetMethod)
{
// If it's abstract, then the method is entirely implemented by the InvocationHandler
if (Method.IsAbstract)
{
base.ImplementBody(il, methodInfoField, propertyInfoField, proceed, proceedTargetMethod);
}
// Otherwise, it is implemented by the class itself, and calling this.Invocation().Proceed() calls the InvocationHandler
else
{
Method.Body.InitLocals = true;
// First declare the invocation in a private local variable
var invocation = new VariableDefinition(ClassWeaver.Context.InvocationType);
var instructions = Method.Body.Instructions.ToList();
Method.Body.Instructions.Clear(); // Wipe out the existing instructions for the method
Method.Body.Variables.Add(invocation); // Add a variable to store the invocation
EmitInvocation(il, methodInfoField, propertyInfoField, proceed); // Put the invocation on the stack
il.Emit(OpCodes.Dup); // Duplicate invocation for below
il.Emit(OpCodes.Stloc, invocation); // Store the invocation in the variable declared (just) earlier
// Add the invocation to the end of the array
il.Emit(OpCodes.Call, ClassWeaver.Context.InvocationGetArguments); // Array now on the stack with the invocation above it
il.Emit(OpCodes.Ldc_I4, Method.Parameters.Count); // Array index
il.Emit(OpCodes.Ldloc, invocation); // Element value
il.Emit(OpCodes.Stelem_Any, ClassWeaver.Context.ModuleDefinition.TypeSystem.Object); // Set array at index to element value
// Special instrumentation for async methods
var returnType = Method.ReturnType;
if (ClassWeaver.Context.TaskType.IsAssignableFrom(returnType))
{
// If the return type is Task<T>
if (returnType.IsTaskT())
{
var actualReturnType = returnType.GetTaskType();
var expectedAsyncBuilder = ClassWeaver.Context.AsyncTaskMethodBuilder.MakeGenericInstanceType(actualReturnType);
// Now find the call to .Start() (only will be found if we're async)
var startInstructionMethod = (GenericInstanceMethod)instructions
.Where(x => x.OpCode == OpCodes.Call)
.Select(x => (MethodReference)x.Operand)
.Where(x => x.IsGenericInstance && x.Name == "Start" && x.DeclaringType.CompareTo(expectedAsyncBuilder))
.SingleOrDefault();
if (startInstructionMethod != null)
{
var asyncType = startInstructionMethod.GenericArguments[0];
var invocationField = InstrumentAsyncType(asyncType);
// Find the first instruction that is setting a field on the async type. We can just assume it's a three instruction
// set (it always is in this context) And we add our instructions to set the invocation field.
var nextSetFieldIndex = instructions.IndexOf(x => x.OpCode == OpCodes.Stfld && x.Operand is FieldDefinition && ((FieldDefinition)x.Operand).DeclaringType.CompareTo(asyncType));
if (nextSetFieldIndex == -1)
{
throw new Exception($"Could not find expected stfld of async type: {asyncType}");
}
var setFieldLoadInstance = instructions[nextSetFieldIndex - 2];
instructions.Insert(nextSetFieldIndex - 2, il.Clone(setFieldLoadInstance));
instructions.Insert(nextSetFieldIndex - 1, il.Create(OpCodes.Ldloc, invocation));
instructions.Insert(nextSetFieldIndex, il.Create(OpCodes.Stfld, invocationField));
}
}
}
InstrumentInstructions(il, instructions, 2, x => x.Emit(OpCodes.Ldloc, invocation));
}
}