[fx] Fix type inference for scalar/int types. (#3099)

This was discovered in a downstream test suite and was due to a control
flow nesting merge issue. In-tree test added and fixed.

python/torch_mlir/extras/fx_importer.py

@@ -927,13 +927,13 @@ class ContextCache:
             tensor_meta = node.meta.get("tensor_meta")
             val = node.meta.get("val")
             sparsity = node.meta.get("sparsity", None)
-            return self.value_info_to_type(
-                val, tensor_meta=tensor_meta, sparsity=sparsity, mutable=mutable
-            )
         except KeyError as e:
             raise RuntimeError(
                 f"FIXME: Illegal access to torch.fx.Node.meta: {e} ({node.meta.keys()} : {node.meta})"
             )
+        return self.value_info_to_type(
+            val, tensor_meta=tensor_meta, sparsity=sparsity, mutable=mutable
+        )
 
     def value_info_to_type(
         self,
@@ -962,13 +962,16 @@ class ContextCache:
                 return self.get_vtensor_type(
                     val.size(), val.dtype, sparsity=sparsity, mutable=mutable
                 )
-        else:
-            t = SCALAR_TYPE_TO_TORCH_MLIR_TYPE.get(type(val))
-            if t is not None:
-                return IrType.parse(t, self._c)
+
+        # Note that None is a valid scalar here, so it is important that this
+        # is always checked as the last fallback.
+        t = SCALAR_TYPE_TO_TORCH_MLIR_TYPE.get(type(val))
+        if t is not None:
+            return IrType.parse(t, self._c)
+
         raise NotImplementedError(
             f"Could not deduce type from value info: "
-            f"tensor_meta={tensor_meta}, val={val}, sparsity={sparsity}"
+            f"tensor_meta={tensor_meta}, val={val} {type(val)}, sparsity={sparsity}"
         )
 
     def tensor_metadata_to_type(
@@ -1631,7 +1634,9 @@ class GraphNodeImporter:
         with loc:
             return cvt(arg, self, self._cc)
 
-    def _unpack_node_result_types(self, node: torch.fx.Node, schema: FunctionSchema) -> List[IrType]:
+    def _unpack_node_result_types(
+        self, node: torch.fx.Node, schema: FunctionSchema
+    ) -> List[IrType]:
         return_count = len(schema.returns)
         if return_count == 1:
             # Unary return directly maps a single meta["val"] and cannot be subscripted.

test/python/fx_importer/v2.3/types_test.py

@@ -0,0 +1,43 @@
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+# Also available under a BSD-style license. See LICENSE.
+
+# RUN: %PYTHON %s | FileCheck %s
+# This file contains tests of various op special forms that the fx_importer
+# handles.
+
+from typing import Optional
+
+import torch
+import torch.export
+import torch.nn as nn
+
+from torch_mlir import fx
+
+
+def run(f):
+    print(f"{f.__name__}")
+    print("-" * len(f.__name__))
+    f()
+    print()
+
+
+@run
+# CHECK-LABEL: test_scalar_typed_node
+# Getting the shape of a dynamic dimension has the side effect of producing
+# a node like:
+#   sym_size_int: "Sym(s0)" = torch.ops.aten.sym_size.int(arg0_1, 0)
+# This tests the fx_importer code paths around resolving scalar/symbolic
+# types for operands and results.
+def test_scalar_typed_node():
+    class Basic(nn.Module):
+        def forward(self, x):
+            x = x + 1.0
+            return x.shape[0]
+
+    # CHECK: torch.aten.size.int %arg0, %int0 : !torch.vtensor<[?,4],f32>, !torch.int -> !torch.int
+    m = fx.export_and_import(
+        Basic(), torch.randn(3, 4), dynamic_shapes={"x": {0: torch.export.Dim("b")}}
+    )
+    print(m)