支持C#8.0的接口默认方法 (#189)

* 支持C#8.0的接口默认方法

* 支持C#8.0接口默认方法, 解决默认方法不拦截的问题

Author: q7164518

core/src/AspectCore.Core/Utils/ProxyGeneratorUtils.cs

@@ -462,7 +462,32 @@ private static MethodBuilder DefineMethod(MethodInfo method, string name, Method
                 var implementationMethod = implType.GetTypeInfo().GetMethodBySignature(method);
                 if (implementationMethod == null)
                 {
-                    throw new MissingMethodException($"Type '{implType}' does not contain a method '{method}'.");
+                    var interfaces = implType.GetInterfaces();
+                    if (interfaces == null || interfaces.Length <= 0)
+                    {
+                        throw new MissingMethodException($"Type '{implType}' does not contain a method '{method}'.");
+                    }
+                    var @interface = interfaces.Where(f => f.GetCustomAttribute(typeof(AbstractInterceptorAttribute)) != null).ToArray();
+                    if (@interface.Length > 0)
+                    {
+                        foreach (var item in @interface)
+                        {
+                            implementationMethod = item.GetTypeInfo().GetMethodBySignature(method);
+                            if (implementationMethod != null) break;
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in interfaces)
+                        {
+                            implementationMethod = item.GetTypeInfo().GetMethodBySignature(method);
+                            if (implementationMethod != null) break;
+                        }
+                    }
+                    if (implementationMethod == null)
+                    {
+                        throw new MissingMethodException($"Type '{implType}' does not contain a method '{method}'.");
+                    }
                 }
 
                 if (method.IsNonAspect())