invalid_deprecated_implement_annotation

The annotation '@Deprecated.implement' can only be applied to implementable classes.

The analyzer produces this diagnostic when the @Deprecated.implement annotation is applied to a declaration that isn't an implementable class or mixin. An implementable class or mixin is one that isn't declared with the base, final, or sealed keywords.

The following code produces this diagnostic because the annotation is on a sealed class:

@Deprecated.implement()
sealed class C {}

Remove the annotation:

sealed class C {}