`isAssignableFrom` does not work for mixins as stated by the docs

[rubenferreira97]

Trying to check if a mixin element type represents a super type I found the following statement documented on isSuperTypeOf():

Returns true if representing a super type of staticType.

This only takes into account the extends hierarchy. If you wish to check mixins and interfaces, use isAssignableFromType.

So with this information I thought that isAssignableFromType would work as it is.

Implementation:

bool isAssignableFromType(DartType staticType) =>
    isAssignableFrom(staticType.element2!);

bool isAssignableFrom(Element element) =>
    isExactly(element) ||
    (element is ClassElement && element.allSupertypes.any(isExactlyType));

However, given that a mixin type is a MixinElement and not a ClassElement, the previous condition fails since element is ClassElement is false.