The problem
Do you get an error like this when working with Unity?
1
Ambiguous reference: JetBrains.Annotations.UsedImplicitlyAttribute JetBrains.Annotations.UsedImplicitlyAttribute match
It’s normal practice, specifically it happens when working with Unity, however after some research I didn’t get a workaround/solution for that, but well I found one solution which is different of what I’ll show so I was only able to use outdated old version of UsedImplicitlyAttribute, which is coming from Unity, not from JetBrains itself, it means I couldn’t use ImplicitUseTargetFlags.WithInheritors option.
Solution
1. Reference JetBrains.Annotations package in .csproj
1
2
3
4
5
6
7
8
9
10
11
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>netstandard2.1</TargetFramework>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="JetBrains.Annotations" Version="2024.2.0" /> <!-- This is need to be added in your .csproj -->
</ItemGroup>
</Project>
2. Create a file in your project/solution named UnityEngineDependentProjectProps.props or any other name and paste there this content:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
<!--
Fixes problem when using JetBrains.Annotations in a project that references UnityEngine.CoreModule.
Example of the problem:
Ambiguous reference: JetBrains.Annotations.UsedImplicitlyAttribute JetBrains.Annotations.UsedImplicitlyAttribute match
-->
<Project>
<ItemGroup>
<Reference Include="UnityEngine.CoreModule" />
<Reference Include="JetBrains.Annotations">
<Aliases>JetBrainsAnnotations</Aliases>
</Reference>
</ItemGroup>
</Project>
3. Reference UnityEngineDependentProjectProps.props in your .csproj.
I store the UnityEngineDependentProjectProps.props file in the root\props of my solution to just in case able to reference it in other projects of my solution.
1
2
3
4
5
6
7
8
9
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>netstandard2.1</TargetFramework>
</PropertyGroup>
<Import Project="$(MSBuildThisFileDirectory)..\props\UnityEngineDependentProjectProps.props"/>
</Project>
4. Use alias and namespace
In every file make sure to have that, and make sure to keep the extern alias JetBrainsAnnotations always first (even before usings), otherwise project won’t compile.
1
2
3
4
5
6
7
extern alias JetBrainsAnnotations;
using JetBrainsAnnotations::JetBrains.Annotations;
using System; // optional, just example
using UnityEngine; // no problem, we can use Unity here also
class SomeCode {}
// etc
Or you can do that in your GlobalUsings.cs
1
2
3
4
extern alias JetBrainsAnnotations;
global using JetBrainsAnnotations::JetBrains.Annotations;
global using System; // optional, just example
global using UnityEngine; // no problem, we can use Unity here also
Conclusion
Finally, we can use [UsedImplicitly(ImplicitUseTargetFlags.WithInheritors)] =)
The only main thing that motivated me to figure it out is to able use new version of ImplicitUseTargetFlags, instead of outdated Unity’s one.