"unmanaged" generic parameter constraint in IL

Question

When I compile the following code:

type Class1<'T when 'T : unmanaged> =
    class end

type Class2<'T> =
    class end

in IL it looks like this:

.class auto ansi serializable nested public Class1`1<T> extends [mscorlib]System.Object

.class auto ansi serializable nested public Class2`1<T> extends [mscorlib]System.Object

Is the unmanaged constraint saved somewhere? If so, where and how can I programatically obtain it?

In this question, I read it is somewhere in the "emdbedded signature file". What is that?

Answer 1

These constraint are located in the entity data stored in FSharpSignatureData managed resource. It is possible to browse them using F# Metadata Reader from F# PowerPack:

public static IList<FSharpGenericParameterConstraint> GetFSharpGenericParameterConstraints(Type genericType, int position)
{
    return GetFSharpGenericParameterConstraints(genericType.GetGenericArguments()[position]);
}

public static IList<FSharpGenericParameterConstraint> GetFSharpGenericParameterConstraints(Type genericParameter)
{
    var declMethod = genericParameter.DeclaringMethod;
    var declType = genericParameter.DeclaringType;
    var fsAsm = FSharpAssembly.FromAssembly(genericParameter.Assembly);
    int pos = genericParameter.GenericParameterPosition;
    var entities = AllEntities(fsAsm.Entities);
    if(declMethod != null)
    {
        var member = entities.SelectMany(e => e.MembersOrValues).First(m => m.ReflectionMemberInfo == declMethod);
        return member.GenericParameters[pos].Constraints;
    }else if(declType != null)
    {
        var entity = entities.First(e => e.ReflectionType == declType);
        return entity.GenericParameters[pos].Constraints;
    }
    return null;
}

private static IEnumerable<FSharpEntity> AllEntities(IEnumerable<FSharpEntity> entities)
{
    return entities.Concat(entities.SelectMany(e => AllEntities(e.NestedEntities)));
}

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bool unmanaged = GetFSharpGenericParameterConstraints(typeof(MyModule.Class1<>), 0).Any(c => c.IsUnmanagedConstraint);