GeneratedDI.cs

namespace CsDI
{
  partial record DI
  {
    IY? _singletonOf_IY;
    IZ? _singletonOf_IZ;

    public void Get(out IX v)
    {
      v = new X(this);
    }

    public void Get(out IY v)
    {
      _singletonOf_IY ??= new Y(this);
      v = _singletonOf_IY;
    }

    public void Get(out IZ v)
    {
      _singletonOf_IZ ??= new Z(this);
      v = _singletonOf_IZ;
    }


  }
}

GeneratedDI.tt

<#
  var dependencies = new []
  {
    Transient("IX", "X")
  , Singleton("IY", "Y")
  , Singleton("IZ", "Z")
  };
#>

namespace CsDI
{
  partial record DI
  {
<# foreach(var dependency in dependencies) { #>
<# if (!dependency.Transient) { #>
    <#=dependency.InterfaceName#>? _singletonOf_<#=dependency.InterfaceName#>;
<# } #>
<# } #>

<# foreach(var dependency in dependencies) { #>
    public void Get(out <#=dependency.InterfaceName#> v)
    {
<# if (!dependency.Transient) { #>
      _singletonOf_<#=dependency.InterfaceName#> ??= new <#=dependency.ClassName#>(this);
      v = _singletonOf_<#=dependency.InterfaceName#>;
<# } else { #>
      v = new <#=dependency.ClassName#>(this);
<# } #>
    }

<# } #>

  }
}

<#+
(string InterfaceName, string ClassName, bool Transient) Transient(string inm, string cnm)
{
  return (inm ?? "<NULL>", cnm ?? "<NULL>", true);
}

(string InterfaceName, string ClassName, bool Transient) Singleton(string inm, string cnm)
{
  return (inm ?? "<NULL>", cnm ?? "<NULL>", false);
}
#>

Program.cs

using CsDI;

var di = new DI();

di.Get(out IX x);

Console.WriteLine(x.Message());

namespace CsDI
{
  interface IZ
  {
    string Message();
  }

  interface IY
  {
    string Message();
  }

  interface IX
  {
    string Message();
  }

  class Z : IZ
  {
    public Z(DI di)
    {
    }

    public string Message()
    {
      return $"Z";
    }
  }

  class Y : IY
  {
    IZ _z;
    public Y(DI di)
    {
      di.Get(out _z);
    }

    public string Message()
    {
      return $"Y: _z:({_z.Message()})";
    }
  }

  class X : IX
  {
    IY _y;
    IZ _z;
    public X(DI di)
    {
      di.Get(out _y);
      di.Get(out _z);
    }

    public string Message()
    {
      return $"X: _y:({_y.Message()}), _z:({_z.Message()})";
    }
  }
}