Matrix hstack/vstack improved

Closes sympy/sympy#11944

// edited by skirpichev

Based on sympy/sympy#11951

Signed-off-by: Sergey B Kirpichev <skirpichev@gmail.com>

diofant/matrices/matrices.py

@@ -3764,7 +3764,8 @@ def hstack(cls, *args):
         [0, 1, 0, 2]])
 
         """
-        return reduce(cls.row_join, args)
+        _cls = type(args[0])
+        return reduce(_cls.row_join, args)
 
     @classmethod
     def vstack(cls, *args):
@@ -3782,7 +3783,8 @@ def vstack(cls, *args):
         [0, 2]])
 
         """
-        return reduce(cls.col_join, args)
+        _cls = type(args[0])
+        return reduce(_cls.col_join, args)
 
     def row_join(self, rhs):
         """Concatenates two matrices along self's last and rhs's first column

diofant/tests/matrices/test_matrices.py

@@ -2688,3 +2688,10 @@ def test_sympyissue_10770():
             f = getattr(M, op)
             new = f(m) if 'join' in op else f(42, m)
             assert new == m and id(new) != id(m)
+
+
+def test_sympyissue_11944():
+    A = Matrix([[1]])
+    AIm = A.as_immutable()
+    assert Matrix.hstack(AIm, A) == Matrix([[1, 1]])
+    assert Matrix.vstack(AIm, A) == Matrix([[1], [1]])