1. A method comprising: detecting, by a computer in a computer system, an error generating change at a specific location in source code of an application, the source code conforming to a dynamically typed programming language, the detecting including: detecting a change in a signature of a class or a method of the source code, and determining a dependency of a changed portion of the source code based on a type check level, the dependency including: in an event the type check level is a class level type check, a portion of the source code that is dependent on the class having the changed portion, and in an event the type check level is a method level type check, a portion of the source code that is dependent on the method having the changed portion; performing an offline type check on the changed portion of the source code and the dependency of the source code without executing the source code to identify an error, the error to be detected including a data type mismatch error; generating, by the computer, an error message containing information of the error, the information including at least one of (i) an indication of the change in source code, (ii) the specific location, or (iii) reason for the error; and storing, by the computer, the error message.