Weird bug initialising SkyCoord from list of SkyCoords that have distances set #5209

In [13]: from astropy.coordinates import EarthLocation, SkyCoord, GCRS, AltAz
In [13]: from astropy import units as u
In [13]: from astropy.time import Time
In [13]: time = Time("2014-01-20 22:00")
In [13]: location = EarthLocation.from_geodetic(-17.88*u.deg, -28.76*u.deg, 2327*u.m)
In [13]: gcrs_loc = u.Quantity([1712675, 5328049, -3053885], unit=u.m)
In [13]: gcrs_vel = u.Quantity([-388, 125, 0], unit=u.m/u.s)
In [13]: m31 = SkyCoord(10.6847083*u.deg, 41.26875*u.deg)
In [13]: moon = SkyCoord(GCRS(172.4*u.deg, 0.51*u.deg, 0.002671*u.au,
                obstime=time, obsgeoloc=gcrs_loc, obsgeovel=gcrs_vel))

In [13]: SkyCoord(m31)
Out[13]: 
<SkyCoord (ICRS): (ra, dec) in deg
    (10.6847083, 41.26875)>
In [14]: SkyCoord([m31, m31])  # m31 works fine!
Out[14]: 
<SkyCoord (ICRS): (ra, dec) in deg
    [(10.6847083, 41.26875), (10.6847083, 41.26875)]>

In [4]: SkyCoord(moon)
Out[4]: 
<SkyCoord (GCRS: obstime=2014-01-20 22:00:00.000, obsgeoloc=[ 1712675.  5328049. -3053885.] m, obsgeovel=[-388.  125.    0.] m / s): (ra, dec, distance) in (deg, deg, AU)
    (172.4, 0.51, 0.002671)>

In [5]: SkyCoord([moon])  # ODD! Where has the distance gone?
Out[5]: 
<SkyCoord (ICRS): (ra, dec) in deg
    (172.4, 0.51)>

In [6]: SkyCoord([moon, moon]) 
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-6-d318e9f1252e> in <module>()
----> 1 SkyCoord([moon, moon])

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in __init__(self, *args, **kwargs)
    194         args = list(args)  # Make it mutable
    195         copy = kwargs.pop('copy', True)
--> 196         kwargs = self._parse_inputs(args, kwargs)
    197 
    198         # Set internal versions of object state attributes

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in _parse_inputs(self, args, kwargs)
    294                 # along with any frame attributes like equinox or obstime which
    295                 # were explicitly specified in the coordinate object (i.e. non-default).
--> 296                 coord_kwargs = _parse_coordinate_arg(args[0], frame, units, kwargs)
    297 
    298                 # Copy other 'info' attr only if it has actually been defined.

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in _parse_coordinate_arg(coords, frame, units, init_kwargs)
   1486             allunitsphrepr = True
   1487             for sc in scs[1:]:
-> 1488                 if not sc.is_equivalent_frame(scs[0]):
   1489                     raise ValueError("List of inputs don't have equivalent "
   1490                                      "frames: {0} != {1}".format(sc, scs[0]))

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in is_equivalent_frame(self, other)
    602 
    603             for fattrnm in FRAME_ATTR_NAMES_SET():
--> 604                 if getattr(self, fattrnm) != getattr(other, fattrnm):
    605                     return False
    606             return True

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

In [8]: moon.icrs
Out[8]: 
<SkyCoord (ICRS): (ra, dec, distance) in (deg, deg, AU)
    (122.91386538, 19.98343108, 0.98321877)>

In [9]: SkyCoord(moon.icrs)
Out[9]: 
<SkyCoord (ICRS): (ra, dec, distance) in (deg, deg, AU)
    (122.91386538, 19.98343108, 0.98321877)>

In [10]: SkyCoord([moon.icrs])  # ODD! Where has the distance gone?
Out[10]: 
<SkyCoord (ICRS): (ra, dec) in deg
    (122.91386538, 19.98343108)>

In [11]: SkyCoord([moon.icrs, moon.icrs])
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-11-5ca3644d5d2e> in <module>()
----> 1 SkyCoord([moon.icrs, moon.icrs])

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in __init__(self, *args, **kwargs)
    194         args = list(args)  # Make it mutable
    195         copy = kwargs.pop('copy', True)
--> 196         kwargs = self._parse_inputs(args, kwargs)
    197 
    198         # Set internal versions of object state attributes

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in _parse_inputs(self, args, kwargs)
    294                 # along with any frame attributes like equinox or obstime which
    295                 # were explicitly specified in the coordinate object (i.e. non-default).
--> 296                 coord_kwargs = _parse_coordinate_arg(args[0], frame, units, kwargs)
    297 
    298                 # Copy other 'info' attr only if it has actually been defined.

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in _parse_coordinate_arg(coords, frame, units, init_kwargs)
   1486             allunitsphrepr = True
   1487             for sc in scs[1:]:
-> 1488                 if not sc.is_equivalent_frame(scs[0]):
   1489                     raise ValueError("List of inputs don't have equivalent "
   1490                                      "frames: {0} != {1}".format(sc, scs[0]))

/usr/local/lib/python3.5/site-packages/astropy/coordinates/sky_coordinate.py in is_equivalent_frame(self, other)
    602 
    603             for fattrnm in FRAME_ATTR_NAMES_SET():
--> 604                 if getattr(self, fattrnm) != getattr(other, fattrnm):
    605                     return False
    606             return True

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()