Raise IndexError if matrix index out of bounds

Closes #318

mpmath/matrices/matrices.py

@@ -454,6 +454,8 @@ class _matrix:
                     raise IndexError('Row index out of bounds')
             else:
                 # Single row
+                if key[0] >= self.__rows:
+                    raise IndexError('Row index out of bounds')
                 rows = [key[0]]
 
             # Columns
@@ -468,6 +470,8 @@ class _matrix:
 
             else:
                 # Single column
+                if key[1] >= self.__cols:
+                    raise IndexError('Column index out of bounds')
                 columns = [key[1]]
 
             # Create matrix slice

mpmath/tests/test_matrices.py

@@ -49,6 +49,8 @@ def test_matrix_basic():
     assert A9 != A10
     assert nstr(A9)
     assert A9 != None  # issue 283
+    pytest.raises(IndexError, lambda: zeros(1,1)[:, 1])  # issue 318
+    pytest.raises(IndexError, lambda: zeros(1,1)[1, :])
 
 def test_matmul():
     """