fix split_bases and split_indices for ElementVector (#1091)

README.md

@@ -209,6 +209,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html)
 with respect to documented and/or tested features.
 
+### Unreleased
+
+- Fixed: `ElementVector` works also for split_bases/split_indices in case `mesh.dim() != elem.dim`
+
 ### [9.0.0] - 2023-12-24
 
 - Removed: Python 3.7 support

skfem/assembly/basis/abstract_basis.py

@@ -338,7 +338,7 @@ def split_indices(self) -> List[ndarray]:
                                e.interior_dofs])
             return output
         elif isinstance(self.elem, ElementVector):
-            ndims = self.mesh.dim()
+            ndims = self.elem.dim
             e = self.elem.elem
             for k in range(ndims):
                 output.append(np.concatenate((
@@ -359,7 +359,7 @@ def split_bases(self) -> List['AbstractBasis']:
         elif isinstance(self.elem, ElementVector):
             return [type(self)(self.mesh, self.elem.elem, self.mapping,
                                quadrature=self.quadrature)
-                    for _ in range(self.mesh.dim())]
+                    for _ in range(self.elem.dim)]
         return [self]
 
     @property