Don't fold `aten.detach` if result isn't same type as input. (#2824)

We were seeing some assertion failures after some checks around folders
were tightened up in LLVM:
https://github.com/llvm/llvm-project/pull/75887 . This PR essentially
moves the logic that used to be applied at the LLVM level into the
folder, which seems to be the suggested fix.

I'm not sure if the IR that caused issues for us _should_ be valid?
```
%1 = torch.aten.detach %arg0 : !torch.tensor<[1],f32> -> !torch.tensor
```
A better fix might be to create a verifier ensuring the result of
`aten.detach` has the same type as its operand.

---------

Co-authored-by: aaron-stgeorge <aaron.stgeorge@getcruise.com>

lib/Dialect/Torch/IR/TorchOps.cpp

@@ -1465,7 +1465,11 @@ static OpFoldResult intComparatorFoldHelper(OpTy op,
 // AtenDetachOp
 //===----------------------------------------------------------------------===//
 
-OpFoldResult AtenDetachOp::fold(FoldAdaptor adaptor) { return getSelf(); }
+OpFoldResult AtenDetachOp::fold(FoldAdaptor adaptor) {
+  if (getSelf().getType() != getResult().getType())
+    return {};
+  return getSelf();
+}
 
 //===----------------------------------------------------------------------===//
 // AtenNeIntOp

test/Dialect/Torch/canonicalize.mlir

@@ -2146,3 +2146,10 @@ func.func @torch.aten.masked_fill.Tensor$canonicalize(%arg0: !torch.vtensor<[?,?
   %1 = torch.aten.masked_fill.Tensor %arg0, %arg1, %0 : !torch.vtensor<[?,?],f32>, !torch.vtensor<[?,?],i1>, !torch.vtensor<[],f32> -> !torch.vtensor<[?,?],f32>
   return %1 : !torch.vtensor<[?,?],f32>
 }
+
+// CHECK-LABEL:   func.func @torch.aten.detach$canonicalize
+// CHECK-NEXT:      torch.aten.detach
+func.func @torch.aten.detach$canonicalize(%arg0: !torch.tensor<[1],f32>) -> !torch.tensor {
+  %1 = torch.aten.detach %arg0 : !torch.tensor<[1],f32> -> !torch.tensor
+  return %1 : !torch.tensor
+}