MAINT: remove explicit complex128 from fft assertions, of real<->complex

Reuse real_dtype_for/complex_dtype_for, which encapsulate the same mappings.

Author: ev-br

array_api_tests/pytest_helpers.py

@@ -161,11 +161,8 @@ def assert_dtype(
 def assert_float_to_complex_dtype(
     func_name: str, *, in_dtype: DataType, out_dtype: DataType
 ):
-    if in_dtype == xp.float32:
-        expected = xp.complex64
-    else:
-        assert in_dtype == xp.float64  # sanity check
-        expected = xp.complex128
+    assert in_dtype in dh.real_float_dtypes   # sanity check
+    expected = dh.complex_dtype_for(in_dtype)
     assert_dtype(
         func_name, in_dtype=in_dtype, out_dtype=out_dtype, expected=expected
     )
@@ -174,13 +171,8 @@ def assert_float_to_complex_dtype(
 def assert_complex_to_float_dtype(
     func_name: str, *, in_dtype: DataType, out_dtype: DataType, repr_name: str = "out.dtype"
 ):
-    if in_dtype == xp.complex64:
-        expected = xp.float32
-    elif in_dtype == xp.complex128:
-        expected = xp.float64
-    else:
-        assert in_dtype in (xp.float32, xp.float64)  # sanity check
-        expected = in_dtype
+    assert in_dtype in dh.all_float_dtypes
+    expected = dh.real_dtype_for(in_dtype)
     assert_dtype(
         func_name, in_dtype=in_dtype, out_dtype=out_dtype, expected=expected, repr_name=repr_name
     )