no longer DetachFromDisposeScope in set_grad

Author: yueyinqiu

RELEASENOTES.md

@@ -9,6 +9,7 @@ __Breaking Changes__:
 __API Changes__:
 
 - #1291 `Tensor.grad()` and `Tensor.set_grad()` have been replaced by a new property `Tensor.grad`.
+    - A potential memory leak caused by `set_grad` has been resolved.
 
 __Bug Fixes__:
 

src/TorchSharp/NN/Module.cs

@@ -254,14 +254,15 @@ private void _toEpilog(ScalarType? dtype, Device device)
                         // disable grad we would need to call .detach() on the moved tensor.
                         using (var d = torch.no_grad()) {
                             p = new Parameter(
-                                param.to(paramType, device ?? param.device).DetachFromDisposeScope(), param.requires_grad)
-                                .DetachFromDisposeScope() as Parameter;
+                                data: param.to(paramType, device ?? param.device),
+                                requires_grad: param.requires_grad);
+                            _ = p.DetachFromDisposeScope();
 
                             // Copy the gradient over as well, if it exists
                             if (grad is not null) {
-                                p.grad = grad.to(paramType, device ?? param.device)
-                                    .with_requires_grad(grad.requires_grad)
-                                    .MoveToOtherDisposeScope(p);
+                                using var newGrad = grad.to(paramType, device ?? param.device)
+                                    .with_requires_grad(grad.requires_grad);
+                                p.grad = newGrad;
                             }
 
                             // Dispose the param

src/TorchSharp/Tensor/Tensor.cs

@@ -1352,7 +1352,6 @@ public Tensor? grad {
                     return new Tensor(res);
                 }
                 set {
-                    _ = value?.DetachFromDisposeScope();
                     NativeMethods.THSTensor_set_grad(Handle, value?.Handle ?? IntPtr.Zero);
                     CheckForErrors();
                 }