Pandas Setting values with multiindex .loc

Code Sample

df = pd.DataFrame({'A':[1,2,3],'B':[4,5,6]})
df = df.stack()
df.loc[0] = [0,0]

This returns

In [27]: df
Out[27]:
0  A    0
   B    0
1  A    2
   B    5
2  A    3
   B    6
dtype: int64

Then, if I try

df.loc[0] = df.loc[1]

I get

In [29]: df
Out[29]:
0  A    NaN
   B    NaN
1  A    2.0
   B    5.0
2  A    3.0
   B    6.0
dtype: float64

Expected Output

It should either raise an exception/warning, or produce the same result with df.loc[0] = df.loc[1].values.

Comment From: jreback

duplicate of https://github.com/pandas-dev/pandas/issues/10440

a PR to fix is welcome. This should just work, but as lots of issues related to MultiIndex setting, so would welcome some help here.

Comment From: jreback

cc @toobaz

Comment From: toobaz

Yes, it is also related to #12313, which is basically the same problem when the MultiIndex is on the columns, rather than on the rows. I'm pretty sure we want to support this eventually, but might take time.