godot-docs/tutorials/scripting/c_sharp/diagnostics/GD0202.rst

GD0202: The parameter of the delegate signature of the signal is not supported
==============================================================================

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                                      Value
====================================  ======================================
**Rule ID**                           GD0202
**Category**                          Usage
**Fix is breaking or non-breaking**   Breaking - If the parameter type is changed

                                      Non-breaking - If the ``[Signal]`` attribute is removed
**Enabled by default**                Yes
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Cause
-----

An unsupported type is specified for a parameter of a delegate annotated with
the ``[Signal]`` attribute when a
:ref:`Variant-compatible type <c_sharp_variant_compatible_types>` is expected.

Rule description
----------------

Every signal parameter must be Variant-compatible so it can be marshalled when
emitting the signal and invoking the callbacks.

.. code-block:: csharp

    class SomeType { }

    // SomeType is not a valid parameter type because it doesn't derive from GodotObject,
    // so it's not compatible with Variant.
    public void InvalidSignalEventHandler(SomeType someType);

    // System.Int32 is a valid type because it's compatible with Variant.
    public void ValidSignalEventHandler(int someInt);

Take a look at the :ref:`C# signals <doc_c_sharp_signals>` documentation for more
information about how to declare and use signals.

How to fix violations
---------------------

To fix a violation of this rule, change the parameter type to be Variant-compatible
or remove the ``[Signal]`` attribute from the delegate. Note that removing the
attribute will mean the signal is not registered.

.. tip::

    If the signal doesn't need to interact with Godot, consider using
    `C# events <https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/events/>`_
    directly. Pure C# events allow you to use any C# type for its parameters.

When to suppress warnings
-------------------------

Do not suppress a warning from this rule. Signal delegates with parameters that
can't be marshalled will result in runtime errors when emitting the signal or
invoking the callbacks.