Init does not use __new__ arguments (#173)

`__new__` is only used when constructing the class from Python.

To add factory methods in Zig, they should be wrapped in `py.zig`

example/iterators.pyi

@@ -10,8 +10,10 @@ class Range:
         ...
 
 class RangeIterator:
-    def __init__(next, stop, step, /):
-        pass
+    """
+    Range iterator
+    """
+
     def __next__(self, /):
         """
         Implement next(self).

example/iterators.zig

@@ -40,10 +40,6 @@ pub const RangeIterator = py.class(struct {
     stop: i64,
     step: i64,
 
-    pub fn __new__(args: struct { next: i64, stop: i64, step: i64 }) Self {
-        return .{ .next = args.next, .stop = args.stop, .step = args.step };
-    }
-
     pub fn __next__(self: *Self) ?i64 {
         if (self.next >= self.stop) {
             return null;

pydust/src/pydust.zig

@@ -40,7 +40,7 @@ pub fn finalize() void {
 }
 
 /// Instantiate a class defined in Pydust.
-pub fn init(comptime Cls: type, args: NewArgs(Cls)) PyError!*Cls {
+pub fn init(comptime Cls: type, args: Cls) PyError!*Cls {
     const moduleDefinition = State.getContaining(Cls, .module);
     const imported = try types.PyModule.import(State.getIdentifier(moduleDefinition).name);
     const pytype = try imported.obj.get(State.getIdentifier(Cls).name);
@@ -49,29 +49,11 @@ pub fn init(comptime Cls: type, args: NewArgs(Cls)) PyError!*Cls {
     // NOTE(ngates): we currently don't allow users to override tp_alloc, therefore we can shortcut
     // using ffi.PyType_GetSlot(tp_alloc) since we know it will always return ffi.PyType_GenericAlloc
     const pyobj: *pytypes.PyTypeStruct(Cls) = @alignCast(@ptrCast(ffi.PyType_GenericAlloc(@ptrCast(pytype.py), 0) orelse return PyError.PyRaised));
-
-    if (@hasDecl(Cls, "__new__")) {
-        pyobj.state = try tramp.coerceError(Cls.__new__(args));
-    } else if (@typeInfo(Cls).Struct.fields.len > 0) {
-        pyobj.state = args;
-    }
+    pyobj.state = args;
 
     return &pyobj.state;
 }
 
-/// Find the type of the positional args for a class
-inline fn NewArgs(comptime Cls: type) type {
-    if (!@hasDecl(Cls, "__new__")) {
-        // Default construct args are the struct fields themselves.
-        return Cls;
-    }
-
-    const func = @field(Cls, "__new__");
-    const typeInfo = @typeInfo(@TypeOf(func));
-    const sig = funcs.parseSignature("__new__", typeInfo.Fn, &.{});
-    return sig.argsParam orelse struct {};
-}
-
 /// Register the root Pydust module
 pub fn rootmodule(comptime definition: type) void {
     if (!State.isEmpty()) {