COMPAT: avoid invalid buffer comparisions

closes pandas-dev#18064

Author: jreback

pandas/_libs/src/inference.pyx

@@ -613,7 +613,7 @@ cdef class Validator:
         self.dtype = dtype
         self.skipna = skipna
 
-    cdef bint validate(self, object[:] values) except -1:
+    cdef bint validate(self, ndarray values) except -1:
         if not self.n:
             return False
 
@@ -629,7 +629,7 @@ cdef class Validator:
 
     @cython.wraparound(False)
     @cython.boundscheck(False)
-    cdef bint _validate(self, object[:] values) except -1:
+    cdef bint _validate(self, ndarray values) except -1:
         cdef:
             Py_ssize_t i
             Py_ssize_t n = self.n
@@ -642,7 +642,7 @@ cdef class Validator:
 
     @cython.wraparound(False)
     @cython.boundscheck(False)
-    cdef bint _validate_skipna(self, object[:] values) except -1:
+    cdef bint _validate_skipna(self, ndarray values) except -1:
         cdef:
             Py_ssize_t i
             Py_ssize_t n = self.n