[export] Minor fixes to contrain_as_size (pytorch#106737)

Fixed some minor issues with constraint APIs while I was helping enable some other model

Pull Request resolved: pytorch#106737
Approved by: https://github.com/tugsbayasgalan

Author: angelayi

torch/_meta_registrations.py

@@ -397,12 +397,12 @@ def make_dep_token(
 
 
 @register_meta(aten.sym_constrain_range.default)
-def sym_constrain_range(size, min, max):
+def sym_constrain_range(size, min=None, max=None):
     constrain_range(size, min=min, max=max)
 
 
 @register_meta(aten._functional_sym_constrain_range.default)
-def functional_sym_constrain_range(size, min, max, dep_token):
+def functional_sym_constrain_range(size, min=None, max=None, dep_token=None):
     aten.sym_constrain_range(size, min=min, max=max)
     return dep_token
 

torch/fx/experimental/symbolic_shapes.py

@@ -374,6 +374,10 @@ def constrain_range_int(a, *, min, max):
     - During tracing the traced symbol is resolved as a static integer (see
       PR #101655 for more details).
     """
+    if min is None:
+        min = -sympy.oo
+    if max is None:
+        max = sympy.oo
 
     assert not isinstance(a, SymInt)
     if not (min <= a <= max):