CLN: Delay converting bins to datelike until necessary (pandas-dev#21724)

Author: mroeschke

pandas/core/reshape/tile.py

@@ -235,7 +235,7 @@ def cut(x, bins, right=True, labels=None, retbins=False, precision=3,
  duplicates=duplicates)
 
  return _postprocess_for_cut(fac, bins, retbins, x_is_series,
- series_index, name)
+ series_index, name, dtype)
 
 
 def qcut(x, q, labels=None, retbins=False, precision=3, duplicates='raise'):
@@ -307,7 +307,7 @@ def qcut(x, q, labels=None, retbins=False, precision=3, duplicates='raise'):
  dtype=dtype, duplicates=duplicates)
 
  return _postprocess_for_cut(fac, bins, retbins, x_is_series,
- series_index, name)
+ series_index, name, dtype)
 
 
 def _bins_to_cuts(x, bins, right=True, labels=None,
@@ -365,8 +365,6 @@ def _bins_to_cuts(x, bins, right=True, labels=None,
  result = result.astype(np.float64)
  np.putmask(result, na_mask, np.nan)
 
- bins = _convert_bin_to_datelike_type(bins, dtype)
-
  return result, bins
 
 
@@ -511,7 +509,7 @@ def _preprocess_for_cut(x):
 
 
 def _postprocess_for_cut(fac, bins, retbins, x_is_series,
- series_index, name):
+ series_index, name, dtype):
  """
  handles post processing for the cut method where
  we combine the index information if the originally passed
@@ -523,6 +521,8 @@ def _postprocess_for_cut(fac, bins, retbins, x_is_series,
  if not retbins:
  return fac
 
+ bins = _convert_bin_to_datelike_type(bins, dtype)
+
  return fac, bins