Signal an error if heuresticate-types failes to parse a timestamp

Author: tre-flip

src/properties.lisp

@@ -14,14 +14,9 @@ Often when reading in a data set, the types will be inconsistent in a variable.
 				(sym (find-symbol (symbol-name key) (find-package name))))
 		   (setf (get sym :type) col-type)
 		   ;; If a column is :temporal, replace strings in it with timestamps.
-		   ;; If local-time fails to parse a value then leave it as is.
+		   ;; If local-time fails to parse a value then signal an error without corrupting the dataframe.
 		   (when (eql col-type :temporal)
-			 (map-into data
-					   #'(lambda (val)
-						   (or (when (stringp val)
-								 (local-time:parse-timestring val :fail-on-error nil))
-							   val))
-					   data))))
+			 (setf (column df key) (map 'vector #'local-time:parse-timestring data)))))
 	 (keys df))))
 
 (defun set-properties (df property prop-values)