Added return is_integer(element) or is_float(element) to the IntBlock._can_hold_element method because an Block of ints can be replaced from int read https://github.com/pandas-dev/pandas/issues/35376 for more infos

is_float added to IntBlock._can_hold_element

Index: pandas/core/internals/blocks.py
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- pandas/core/internals/blocks.py	(revision 1b2f1f47b90fe585b8a01705482b1193aa281393)
+++ pandas/core/internals/blocks.py	(date 1600372421300)
@@ -38,6 +38,7 @@
     is_extension_array_dtype,
     is_float_dtype,
     is_integer,
+    is_float,
     is_integer_dtype,
     is_interval_dtype,
     is_list_like,
@@ -2066,7 +2067,7 @@
                 and not issubclass(tipo.type, (np.datetime64, np.timedelta64))
                 and self.dtype.itemsize >= tipo.itemsize
             )
-        return is_integer(element)
+        return is_integer(element) or is_float(element)
 
 
 class DatetimeLikeBlockMixin: