While it's true that it's bad design for these warnings to show up, it's also bad practice to declare inspector properties without initializing them with default values. Initialize your inspector property variables with default values to eliminate the warnings.

very poor design

This is not a good solution.

@Xavier78 I strongly disagree. In my view it's almost always bad practice to assign to [SerializeField] fields from code. These fields are for data to be injected by Unity and in most cases should be essentially immutable from the code's perspective.

Given this - which is of course an opinion, but one that has served me very well - the warning actively discourages good practice.

Okay so I have been dealing with this for a while. The warning should still be there, and this is why. If a private field has a property, or gets assigned to from a public method, this warning will go away. If a private serialized field doesn't have one of those two things then it is bad. Clearly that variable needs to be assigned to by hand since you are showing it to the editor, so there should be a way to assign to it from code side as well. I would suggest if you don't want to use prop, then use a Setup() method that has all serialized fields assigned to, which will make your code more suitable for unit testing in the future. I sincerely hope they do not get rid of this warning for [SerializedFeilds] as that would make wrong coding practices accepted.

So Unity's just going to wait for the compiler to fix it? Pretty disappointing considering JetBrains fixed this problem in Rider a long time ago.

Why has this not been fixed yet?

This is fixed for .Net 3.5, but is not fixed for .Net 4.X

Labelling this as "by design" is, frankly, absurd. It actively opposes the purpose of warnings. In this case a warning is issued when the programmer uses good practice, thus discouraging it. Warnings are designed specifically to discourage bad practices.

Boo bad design. Not sure why this could slip through. I guess we want newer Roslyn and this is what we get. Honestly this is a long standing issue that Unity should address in an alternative way. On compile complete if warning cs0649 is field SerializedField... yes? Don't show the stinking warning! Why rely and wait on Roslyn to get fixed? You have control over what is displayed in the console.