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Fixed in 2021.1.X

Fixed in 2018.4.X, 2019.4.X, 2020.1.X, 2020.2.X



Found in



Issue ID




[SerializedField] fields produce "Field is never assigned to..." warning



1. Open the attached project (
2. Observe the warning in the console

Expected: field with SerializeField attribute do not produce the warning

Reproduced in 2018.3.0a1, 2018.3.0b1, 2018.3.0b2, 2019.1.0a1
Did not reproduce in 2018.2.8f1
Regression introduced in 2018.3.0a1

  1. Response avatar


    Nov 06, 2019

    #pragma warning disable 0649
    // your code
    #pragma warning restore 0649

    Or disable it globally by adding a file named csc.rsp to the root of you Assets folder, e.g. Assets/csc.rsp, with the following contents without quotes.


    This will tell the C# compiler to not emit a warning for CS0649 / unused fields.

    If you have .asmdefs with csc.rsp in your project, then you also need to add the "/nowarn:0649" line to those csc.rsp files.

  1. Response avatar

    Resolution Note (fix version 2021.1):

    A list where you can pass additional compiler arguments as well as a toggle to suppress common warnings is added in the Player Settings
    Fixed in 2021.1.0a2

  2. Response avatar

    Resolution Note (fix version 2020.2):

    Fixed in 2020.2.0b9

  3. Response avatar

    Resolution Note (fix version 2020.1):

    Fixed in 2020.1.11f1

  4. Response avatar

    Resolution Note (fix version 2019.4):

    Fixed in 2019.4.15f1

  5. Response avatar

    Resolution Note (fix version 2018.4):

    Fixed in 2018.4.29f1

Comments (82)

  1. Cb0088335925614ac61657710cac4207?d=mm


    Apr 16, 2019 18:00

    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.

  2. Ba5acdfbdf2a33ddaae2e55ebdb45293?d=mm


    Apr 13, 2019 13:47

    very poor design

  3. 162782902a85928256d1d1e7b617ab78?d=mm


    Apr 11, 2019 05:52

    This is not a good solution.

  4. F9440774552a4e4217bc66136867b935?d=mm


    Apr 07, 2019 11:58

    @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.

  5. D9105352c7a09434ff8fb69b76eb1ad9?d=mm


    Mar 21, 2019 02:09

    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.

  6. 03b5422b519c51eb98f03f25678712d8?d=mm


    Mar 05, 2019 18:27

    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.

  7. D9105352c7a09434ff8fb69b76eb1ad9?d=mm


    Feb 20, 2019 08:41

    Why has this not been fixed yet?

  8. D998d5758d57fa06af2b545cf804fca0?d=mm


    Feb 14, 2019 22:23

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

  9. F9440774552a4e4217bc66136867b935?d=mm


    Feb 09, 2019 13:51

    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.

  10. 42b11a402b6a4c0e2afc8a73172580f9?d=mm


    Feb 01, 2019 06:40

    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.

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