Fix: return NotNullIfNotNull

[nan01ab]

#3702 not works.

• Optimization (the change is only an optimization)
• Style (the change is only a code style for better maintenance or standard purpose)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[cschuchardt88]

factory variable can be still be null

Take for example

var nullValue = GetAndChange(key, () => null);

[nan01ab]

factory variable can be still be null

Take for example

var nullValue = GetAndChange(key, () => null);

The factory definition is Func<StorageItem>
StorageItem, not StorageItem?

[cschuchardt88]

neo is not a nullable project. So it can still be null.

[nan01ab]

neo is not a nullable project. So it can still be null.

https://github.com/neo-project/neo/blob/master/src/Neo/Persistence/DataCache.cs#L12

[cschuchardt88]

That doesnt matter. If the project importing the library isnt nullable it doesnt care. nullable is only for the analyzers for the IDE to not have red line under variable.

with no nullable enabled

with nullable enabled

[cschuchardt88]

They just need to enable nullable in devpack