GenAPI produces invalid source code for record properties

Repro steps in SBRP

1. generate.sh --package "Microsoft.Build,16.10.0" --exclude-package-dependencies
2. ./.dotnet/dotnet build src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj

GenAPI produces the following code:

        public virtual GraphBuildOptions <Clone>$() { throw null; }

Errors

/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net472/Microsoft.Build.cs(2559,49): error CS1519: Invalid token '$' in class, record, struct, or interface member declaration [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net472]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net472/Microsoft.Build.cs(2559,49): error CS1056: Unexpected character '$' [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net472]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net472/Microsoft.Build.cs(2559,51): error CS8124: Tuple must contain at least two elements. [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net472]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net472/Microsoft.Build.cs(2559,53): error CS1519: Invalid token '{' in class, record, struct, or interface member declaration [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net472]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net472/Microsoft.Build.cs(2730,1): error CS1022: Type or namespace definition, or end-of-file expected [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net472]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net5.0/Microsoft.Build.cs(2555,49): error CS1519: Invalid token '$' in class, record, struct, or interface member declaration [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net5.0]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net5.0/Microsoft.Build.cs(2555,49): error CS1056: Unexpected character '$' [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net5.0]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net5.0/Microsoft.Build.cs(2555,51): error CS8124: Tuple must contain at least two elements. [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net5.0]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net5.0/Microsoft.Build.cs(2555,53): error CS1519: Invalid token '{' in class, record, struct, or interface member declaration [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net5.0]
/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/lib/net5.0/Microsoft.Build.cs(2726,1): error CS1022: Type or namespace definition, or end-of-file expected [/home/vihofer/git/source-build-reference-packages/src/referencePackages/src/microsoft.build/16.10.0/Microsoft.Build.16.10.0.csproj::TargetFramework=net5.0]

[ViktorHofer]

Fixed with https://github.com/dotnet/roslyn/issues/67335

[KalleOlaviNiemitalo]

It seems the following members would also need to be generated

partial class GraphBuildOptions
{
    public override string ToString() { throw null; }
    protected virtual bool PrintMembers(System.Text.StringBuilder builder) { throw null; }
    public static bool operator !=(GraphBuildOptions? left, GraphBuildOptions? right) { throw null; }
    public static bool operator ==(GraphBuildOptions? left, GraphBuildOptions? right) { throw null; }
    public override bool Equals(object? obj) { throw null; }
    public bool Equals(GraphBuildOptions? other) { throw null; }
    public override int GetHashCode() { throw null; }
    protected GraphBuildOptions(GraphBuildOptions original) {}
    public GraphBuildOptions() {}
}

but the <Clone>$() method is still a problem. If you consume the reference assembly with this kind of code

static class C
{
    static void M()
    {
        _ = new GraphBuildOptions() with { Build = true };
    }
}

then it tries to call the <Clone>$() method, and fails to compile if that does not exist.

So, I think GenAPI needs to generate the C# record syntax.