initial code

src/ProxyInterfaceSourceGenerator/FileGenerators/ProxyAttributeGenerator.cs

@@ -0,0 +1,30 @@
+namespace ProxyInterfaceSourceGenerator.FileGenerators
+{
+    internal class ProxyAttributeGenerator : IFileGenerator
+    {
+        private const string ClassName = "ProxyAttribute";
+
+        public Data GenerateFile()
+        {
+            return new Data
+            {
+                FileName = $"{ClassName}.cs",
+                Text = $@"using System;
+
+namespace ProxyInterfaceGenerator
+{{
+    [AttributeUsage(AttributeTargets.Interface)]
+    public class {ClassName} : Attribute
+    {{
+        public Type Type {{ get; }}
+
+        public {ClassName}(Type type)
+        {{
+            Type = type;
+        }}
+    }}
+}}"
+            };
+        }
+    }
+}