Check basis against a FreeModuleBasis in FreeModuleTensor._preparse_d…

…isplay

src/sage/tensor/modules/free_module_tensor.py

@@ -197,9 +197,9 @@ class being:
 from sage.tensor.modules.comp import (Components, CompWithSym, CompFullySym,
                                       CompFullyAntiSym)
 from sage.tensor.modules.tensor_with_indices import TensorWithIndices
+from sage.tensor.modules.free_module_basis import FreeModuleBasis
 from sage.parallel.decorate import parallel
 from sage.parallel.parallelism import Parallelism
-from sage.manifolds.chart import Chart
 
 
 class FreeModuleTensor(ModuleElement):
@@ -576,10 +576,11 @@ def _preparse_display(self, basis=None, format_spec=None):
         """
         if basis is None:
             basis = self._fmodule._def_basis
-        elif isinstance(basis, Chart):
-            # a coordinate chart has been passed instead of a basis;
-            # the basis is then assumed to be the coordinate frame
-            # associated to the chart:
+        elif not isinstance(basis, FreeModuleBasis):
+            # basis is assumed to be a "format specification" that carries a
+            # genuine basis via the attribute frame() (this holds for
+            # coordinate charts on manifolds, the basis returned by frame()
+            # being the coordinate vector frame)
             if format_spec is None:
                 format_spec = basis
             basis = basis.frame()