From 9a0ceb698ea83ef726e52e84849ff62c6f5ef053 Mon Sep 17 00:00:00 2001
From: Benedikt Reinartz <filmor@gmail.com>
Date: Sun, 10 Apr 2022 18:12:51 +0200
Subject: [PATCH] Implement IConvertible interface on PyObject

---
 src/runtime/Converter.cs                      |  2 +-
 src/runtime/PythonTypes/PyFloat.cs            |  2 +
 src/runtime/PythonTypes/PyInt.cs              |  2 +
 .../PythonTypes/PyObject.IConvertible.cs      | 53 +++++++++++++++++++
 src/runtime/PythonTypes/PyString.cs           |  2 +
 tests/test_conversion.py                      |  7 +++
 6 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 src/runtime/PythonTypes/PyObject.IConvertible.cs

diff --git a/src/runtime/Converter.cs b/src/runtime/Converter.cs
index a90f31513..a99961aaa 100644
--- a/src/runtime/Converter.cs
+++ b/src/runtime/Converter.cs
@@ -550,7 +550,7 @@ internal static int ToInt32(BorrowedReference value)
         /// <summary>
         /// Convert a Python value to an instance of a primitive managed type.
         /// </summary>
-        private static bool ToPrimitive(BorrowedReference value, Type obType, out object? result, bool setError)
+        internal static bool ToPrimitive(BorrowedReference value, Type obType, out object? result, bool setError)
         {
             result = null;
             if (obType.IsEnum)
diff --git a/src/runtime/PythonTypes/PyFloat.cs b/src/runtime/PythonTypes/PyFloat.cs
index 7fb9e8f4d..10104c10f 100644
--- a/src/runtime/PythonTypes/PyFloat.cs
+++ b/src/runtime/PythonTypes/PyFloat.cs
@@ -101,5 +101,7 @@ public static PyFloat AsFloat(PyObject value)
             PythonException.ThrowIfIsNull(op);
             return new PyFloat(op.Steal());
         }
+
+        public override TypeCode GetTypeCode() => TypeCode.Double;
     }
 }
diff --git a/src/runtime/PythonTypes/PyInt.cs b/src/runtime/PythonTypes/PyInt.cs
index 3dcc6ddb2..6b3dbf210 100644
--- a/src/runtime/PythonTypes/PyInt.cs
+++ b/src/runtime/PythonTypes/PyInt.cs
@@ -230,5 +230,7 @@ public string ToString(string format, IFormatProvider formatProvider)
             using var _ = Py.GIL();
             return ToBigInteger().ToString(format, formatProvider);
         }
+
+        public override TypeCode GetTypeCode() => TypeCode.Int64;
     }
 }
diff --git a/src/runtime/PythonTypes/PyObject.IConvertible.cs b/src/runtime/PythonTypes/PyObject.IConvertible.cs
new file mode 100644
index 000000000..503d3cab4
--- /dev/null
+++ b/src/runtime/PythonTypes/PyObject.IConvertible.cs
@@ -0,0 +1,53 @@
+using System;
+
+namespace Python.Runtime;
+
+public partial class PyObject : IConvertible
+{
+    public virtual TypeCode GetTypeCode() => TypeCode.Object;
+
+    private T DoConvert<T>()
+    {
+        using var _ = Py.GIL();
+        if (Converter.ToPrimitive(Reference, typeof(T), out object? result, setError: false))
+        {
+            return (T)result!;
+        }
+        else
+        {
+            throw new InvalidCastException();
+        }
+    }
+
+    public bool ToBoolean(IFormatProvider provider) => DoConvert<bool>();
+    public byte ToByte(IFormatProvider provider) => DoConvert<byte>();
+    public char ToChar(IFormatProvider provider) => DoConvert<char>();
+    public short ToInt16(IFormatProvider provider) => DoConvert<short>();
+    public int ToInt32(IFormatProvider provider) => DoConvert<int>();
+    public long ToInt64(IFormatProvider provider) => DoConvert<long>();
+    public sbyte ToSByte(IFormatProvider provider) => DoConvert<sbyte>();
+    public ushort ToUInt16(IFormatProvider provider) => DoConvert<ushort>();
+    public uint ToUInt32(IFormatProvider provider) => DoConvert<uint>();
+    public ulong ToUInt64(IFormatProvider provider) => DoConvert<ulong>();
+
+    public float ToSingle(IFormatProvider provider) => DoConvert<float>();
+    public double ToDouble(IFormatProvider provider) => DoConvert<double>();
+
+    public string ToString(IFormatProvider provider) => DoConvert<string>();
+
+    public DateTime ToDateTime(IFormatProvider provider) => throw new InvalidCastException();
+    public decimal ToDecimal(IFormatProvider provider) => throw new InvalidCastException();
+
+    public object ToType(Type conversionType, IFormatProvider provider)
+    {
+        if (Converter.ToManaged(Reference, conversionType, out object? result, setError: false))
+        {
+            return result!;
+        }
+        else
+        {
+            throw new InvalidCastException();
+        }
+    }
+
+}
\ No newline at end of file
diff --git a/src/runtime/PythonTypes/PyString.cs b/src/runtime/PythonTypes/PyString.cs
index cdd45e2c3..d54397fcf 100644
--- a/src/runtime/PythonTypes/PyString.cs
+++ b/src/runtime/PythonTypes/PyString.cs
@@ -59,5 +59,7 @@ public static bool IsStringType(PyObject value)
         {
             return Runtime.PyString_Check(value.obj);
         }
+
+        public override TypeCode GetTypeCode() => TypeCode.String;
     }
 }
diff --git a/tests/test_conversion.py b/tests/test_conversion.py
index 341b11b90..4de286b14 100644
--- a/tests/test_conversion.py
+++ b/tests/test_conversion.py
@@ -670,3 +670,10 @@ def test_int_param_resolution_required():
     data = list(mri.MethodA(0x100000000, 10))
     assert len(data) == 10
     assert data[0] == 0
+
+def test_iconvertible_conversion():
+    change_type = System.Convert.ChangeType
+
+    assert 1024 == change_type(1024, System.Int32)
+    assert 1024 == change_type(1024, System.Int64)
+    assert 1024 == change_type(1024, System.Int16)