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59 lines
2.3 KiB
ReStructuredText
59 lines
2.3 KiB
ReStructuredText
GD0302: The generic type parameter must be annotated with the MustBeVariant attribute
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=====================================================================================
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==================================== ======================================
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Value
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==================================== ======================================
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**Rule ID** GD0302
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**Category** Usage
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**Fix is breaking or non-breaking** Breaking
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**Enabled by default** Yes
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==================================== ======================================
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Cause
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-----
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A generic type is specified for a generic type argument when a
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:ref:`Variant-compatible type <c_sharp_variant_compatible_types>` is expected,
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but the specified generic type is not annotated with the ``[MustBeVariant]``
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attribute.
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Rule description
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----------------
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When a generic type parameter is annotated with the ``[MustBeVariant]`` attribute,
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the generic type is required to be a Variant-compatible type. When the type used
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is also a generic type, this generic type must be annotated with the ``[MustBeVariant]``
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attribute as well. For example, the generic ``Godot.Collections.Array<T>`` type
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only supports items of a type that can be converted to Variant, a generic type
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can be specified if it's properly annotated.
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.. code-block:: csharp
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public void Method1<T>()
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{
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// T is not valid here because it may not a Variant-compatible type.
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var invalidArray = new Godot.Collections.Array<T>();
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}
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public void Method2<[MustBeVariant] T>()
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{
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// T is guaranteed to be a Variant-compatible type because it's annotated
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// with the [MustBeVariant] attribute, so it can be used here.
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var validArray = new Godot.Collections.Array<T>();
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}
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How to fix violations
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---------------------
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To fix a violation of this rule, add the ``[MustBeVariant]`` attribute to the
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generic type that is used as a generic type argument that must be Variant-compatible.
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When to suppress warnings
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-------------------------
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Do not suppress a warning from this rule. API that contains generic type arguments
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annotated with the ``[MustBeVariant]`` attribute usually has this requirement
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because the values will be passed to the engine, if the type can't be marshalled
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it will result in runtime errors.
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