Support hidden fields in code generation

[ArsenHD]

Description

This PR fixes issue #646. Hidden fields have been supported in the engine by @volivan239 . This PR adds support for them on the code generation side.

Let's consider an example. We have class A { int x; } and class B extends A { int x; }. These fields x have the same name, but they are different fields. Let's say we have a variable (of type A or B) and we want to access field x (from class A or B). There are 4 cases:

• Variable of type A accessing x of type A. Here field can be accessed directly.
• Variable of type A accessing x of type B. Here we need a cast to type B and then we are able to access the field.
• Variable of type B accessing x of type A. Here we also need a cast, but to type A.
• Variable of type B accessing x of type B. Here field can be accessed directly.

This logic is now implemented in CgCallableAccessManagerImpl. This class checks if we can call a method with the given arguments and if we can access a field using the given object. Previously, there were no checks for fields, only for methods. Now we check field for accessibility. There are 3 cases:

• Field can be accessed directly (myObj.field)
• Field can be accessed with type cast (((MyClass) myObj).field)
• Field can only be accessed via reflection (e.g. private fields)

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Automated Testing

These tests check the hidden fields functionality.

org.utbot.examples.objects.HiddenFieldAccessModifiersTest
org.utbot.examples.objects.HiddenFieldExampleTest

Manual Scenario

TODO

Checklist (remove irrelevant options):

• The change followed the style guidelines of the UTBot project
• Self-review of the code is passed
• The change contains enough commentaries, particularly in hard-to-understand areas
• New documentation is provided or existed one is altered
• No new warnings
• New tests have been added
• All tests pass locally with my changes

[Damtev]

A problem with RequiresTypeCast?