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