Use sympy for typechecking

Author: inducer

sumpy/symbolic.py

@@ -91,20 +91,20 @@ def _find_symbolic_backend():
 
 # }}}
 
-if USE_SYMENGINE:
-    import symengine as sym
-
-    from pymbolic.interop.symengine import (
-        PymbolicToSymEngineMapper as PymbolicToSympyMapperBase,
-        SymEngineToPymbolicMapper as SympyToPymbolicMapperBase,
-    )
-else:
+if TYPE_CHECKING or not USE_SYMENGINE:
     import sympy as sym
 
     from pymbolic.interop.sympy import (  # type: ignore[assignment]
         PymbolicToSympyMapper as PymbolicToSympyMapperBase,
         SympyToPymbolicMapper as SympyToPymbolicMapperBase,
     )
+else:
+    import symengine as sym
+
+    from pymbolic.interop.symengine import (
+        PymbolicToSymEngineMapper as PymbolicToSympyMapperBase,
+        SymEngineToPymbolicMapper as SympyToPymbolicMapperBase,
+    )
 
 # Symbolic API common to SymEngine and sympy.
 # Before adding a function here, make sure it's present in both modules.

test/test_cse.py

@@ -68,14 +68,15 @@
 # }}}
 
 import sys
+from typing import TYPE_CHECKING
 
 import pytest
 
 import sumpy.symbolic as sym
 from sumpy.cse import cse, postprocess_for_cse, preprocess_for_cse
 
 
-if not sym.USE_SYMENGINE:
+if TYPE_CHECKING or not sym.USE_SYMENGINE:
     from sympy.functions.special.hyper import meijerg
     from sympy.simplify import cse_opts
     from sympy.simplify.cse_opts import sub_post, sub_pre