C#: Separate all classes to dedicated files in CIL extractor

csharp/extractor/Semmle.Extraction.CIL/Entities/CustomAttributeDecoder.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Reflection.Metadata;
+
+namespace Semmle.Extraction.CIL.Entities
+{
+    /// <summary>
+    /// Helper class to decode the attribute structure.
+    /// Note that there are some unhandled cases that should be fixed in due course.
+    /// </summary>
+    internal class CustomAttributeDecoder : ICustomAttributeTypeProvider<Type>
+    {
+        private readonly Context cx;
+        public CustomAttributeDecoder(Context cx) { this.cx = cx; }
+
+        public Type GetPrimitiveType(PrimitiveTypeCode typeCode) => cx.Create(typeCode);
+
+        public Type GetSystemType() => throw new NotImplementedException();
+
+        public Type GetSZArrayType(Type elementType) =>
+            cx.Populate(new ArrayType(cx, elementType));
+
+        public Type GetTypeFromDefinition(MetadataReader reader, TypeDefinitionHandle handle, byte rawTypeKind) =>
+            (Type)cx.Create(handle);
+
+        public Type GetTypeFromReference(MetadataReader reader, TypeReferenceHandle handle, byte rawTypeKind) =>
+            (Type)cx.Create(handle);
+
+        public Type GetTypeFromSerializedName(string name) => throw new NotImplementedException();
+
+        public PrimitiveTypeCode GetUnderlyingEnumType(Type type) => throw new NotImplementedException();
+
+        public bool IsSystemType(Type type) => type is PrimitiveType; // ??
+    }
+}