Remove const from moduleState

pydust/src/builtins.zig

@@ -210,7 +210,7 @@ pub fn len(object: anytype) !usize {
 }
 
 /// Return the runtime module state for a Pydust module definition.
-pub fn moduleState(comptime Module: type) !*const Module {
+pub fn moduleState(comptime Module: type) !*Module {
     if (State.getDefinition(Module).type != .module) {
         @compileError("Not a module definition: " ++ Module);
     }
@@ -279,6 +279,8 @@ pub fn tuple(object: anytype) !py.PyTuple {
     return py.PyTuple.unchecked(.{ .py = pytuple });
 }
 
+/// Return the PyType object for a given Python object.
+/// Returns a borrowed reference.
 pub fn type_(object: anytype) !py.PyType {
     return .{ .obj = .{ .py = @as(
         ?*ffi.PyObject,

pydust/src/types/obj.zig

@@ -110,7 +110,9 @@ pub fn PyObjectMixin(comptime name: []const u8, comptime prefix: []const u8, com
         /// Checked conversion from a PyObject.
         pub fn checked(obj: py.PyObject) !Self {
             if (PyCheck(obj.py) == 0) {
-                return py.TypeError.raiseFmt("expected {s}, found {s}", .{ name, try (try py.str(try py.type_(obj))).asSlice() });
+                const typeName = try py.str(try py.type_(obj));
+                defer typeName.decref();
+                return py.TypeError.raiseFmt("expected {s}, found {s}", .{ name, try typeName.asSlice() });
             }
             return .{ .obj = obj };
         }