BUG: Raise TypeError for mismatched signed/unsigned dtypes

Author: Aniketsy

doc/source/whatsnew/v3.0.0.rst

@@ -958,7 +958,7 @@ Interval
 ^^^^^^^^
 - :meth:`Index.is_monotonic_decreasing`, :meth:`Index.is_monotonic_increasing`, and :meth:`Index.is_unique` could incorrectly be ``False`` for an ``Index`` created from a slice of another ``Index``. (:issue:`57911`)
 - Bug in :func:`interval_range` where start and end numeric types were always cast to 64 bit (:issue:`57268`)
--
+- Construction of :class:`IntervalArray` and :class:`IntervalIndex` from arrays with mismatched signed/unsigned integer dtypes (e.g., ``int64`` and ``uint64``) now raises a :exc:`TypeError` instead of proceeding silently. (:issue:`55715`)
 
 Indexing
 ^^^^^^^^

pandas/core/arrays/interval.py

@@ -533,6 +533,9 @@ def from_arrays(
         copy: bool = False,
         dtype: Dtype | None = None,
     ) -> Self:
+        left = _maybe_convert_platform_interval(left)
+        right = _maybe_convert_platform_interval(right)
+
         # Check for mismatched signed/unsigned integer dtypes
         left_dtype = getattr(left, "dtype", None)
         right_dtype = getattr(right, "dtype", None)
@@ -547,8 +550,6 @@ def from_arrays(
                 f"Left and right arrays must have matching signedness. "
                 f"Got {left_dtype} and {right_dtype}."
             )
-        left = _maybe_convert_platform_interval(left)
-        right = _maybe_convert_platform_interval(right)
 
         left, right, dtype = cls._ensure_simple_new_inputs(
             left,