Output.md

Test_Unconstrained`1
    Name            : T
    Attributes      : None

Test_ConstrainedToObject`1
    Name            : T
    Attributes      : None
    Constraint Kind : TypeReference
    Constraint Type : System.Object

Test_ConstrainedToClass`1
    Name            : T
    Attributes      : ReferenceTypeConstraint

Test_ConstrainedToStruct`1
    Name            : T
    Attributes      : NotNullableValueTypeConstraint, DefaultConstructorConstraint
    Constraint Kind : TypeReference
    Constraint Type : System.ValueType

Program.cs

using System;
using System.IO;
using System.Reflection.Metadata;
using System.Reflection.PortableExecutable;

namespace ConsoleApp26
{
    class Program
    {
        static void Main(string[] args)
        {
            var path = Environment.GetCommandLineArgs()[0];
            using var stream = File.OpenRead(path);
            using var peReader = new PEReader(stream);
            var reader = peReader.GetMetadataReader();

            foreach (var typeHandle in reader.TypeDefinitions)
            {
                var type = reader.GetTypeDefinition(typeHandle);

                if (type.GetGenericParameters().Count == 0)
                    continue;

                Console.WriteLine(reader.GetString(type.Name));

                foreach (var parameterHandle in type.GetGenericParameters())
                {
                    var parameter = reader.GetGenericParameter(parameterHandle);

                    Console.WriteLine($"    Name            : {reader.GetString(parameter.Name)}");
                    Console.WriteLine($"    Attributes      : {parameter.Attributes}");

                    foreach (var constraintHandle in parameter.GetConstraints())
                    {
                        var constraint = reader.GetGenericParameterConstraint(constraintHandle);

                        Console.WriteLine($"    Constraint Kind : {constraint.Type.Kind}");

                        if (constraint.Type.Kind == HandleKind.TypeReference)
                        {
                            var constrainTypeReferenceHandle = (TypeReferenceHandle)constraint.Type;
                            var constrainTypeReference = reader.GetTypeReference(constrainTypeReferenceHandle);
                            Console.WriteLine($"    Constraint Type : {reader.GetString(constrainTypeReference.Namespace)}.{reader.GetString(constrainTypeReference.Name)}");
                        }
                    }
                }

                Console.WriteLine();
            }
        }
    }

    class Test_Unconstrained<T>
    {
    }

    class Test_ConstrainedToObject<T> where T: object
    {
    }

    class Test_ConstrainedToClass<T> where T : class
    {
    }

    class Test_ConstrainedToStruct<T> where T : struct
    {
    }
}