`InvalidCastException`s on generic types from different ALCs can be unhelpful.

[teo-tsirpanis]

I got this error in my build:

System.InvalidCastException:

[A]System.Runtime.CompilerServices.StrongBox`1[Microsoft.Build.Tasks.Git.GitRepository] cannot be cast to [B]System.Runtime.CompilerServices.StrongBox`1[Microsoft.Build.Tasks.Git.GitRepository].

Type A originates from 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.
Type B originates from 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.

Types A and B are the same (and cannot be different since only one SPC can be loaded), which means by process of elimination that the GitRepositoryies in the generic parameters are from different ALCs. But the error message does not indicate that. It can be improved by more deeply analyzing the types to see what doesn't fit.

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Issue Details

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I got this error in my build:

System.InvalidCastException:

[A]System.Runtime.CompilerServices.StrongBox`1[Microsoft.Build.Tasks.Git.GitRepository] cannot be cast to [B]System.Runtime.CompilerServices.StrongBox`1[Microsoft.Build.Tasks.Git.GitRepository].

Type A originates from 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.
Type B originates from 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.

Types A and B are the same (and cannot be different since only one SPC can be loaded), which means by process of elimination that the GitRepositoryies in the generic parameters are from different ALCs. But the error message does not indicate that. It can be improved by more deeply analyzing the types to see what doesn't fit.

Author:	teo-tsirpanis
Assignees:	-
Labels:	area-AssemblyLoader-coreclr, untriaged
Milestone:	-

[KalleOlaviNiemitalo]

Variant generic types will complicate the deeper analysis.

[KalleOlaviNiemitalo]

It might be sufficient and easy to implement if the exception just listed all the unique assemblies from which the types were loaded:

A1::System.Runtime.CompilerServices.StrongBox`1[A2::Microsoft.Build.Tasks.Git.GitRepository] cannot be cast to A1::System.Runtime.CompilerServices.StrongBox`1[A3::Microsoft.Build.Tasks.Git.GitRepository].

Assembly A1 is 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.
Assembly A2 is …
Assembly A3 is …