Name-Based Analysis of Equally Typed Method Arguments

When calling a method that requires multiple arguments, programmers must pass the arguments in the expected order. For statically typed languages, the compiler helps programmers by checking that the type of each argument matches the type of the formal parameter. Unfortunately, types are futile for methods with multiple parameters of the same type. How can a programmer check that equally typed arguments are passed in the correct order? This paper presents two simple, yet effective, static program analyses that detect problems related to the order of equally typed arguments. The key idea is to leverage identifier names to infer the semantics of arguments and their intended positions. The analyses reveal problems that affect the correctness, understandability, and maintainability of a program, such as accidentally reversed arguments and misleading parameter names. Most parts of the analyses are language-agnostic. We evaluate the approach with 24 real-world programs written in Java and C. Our results show the analyses to be effective and efficient. One analysis reveals anomalies in the order of equally typed arguments; it finds 54 relevant problems with a precision of 82 percent. The other analysis warns about misleading parameter names and finds 31 naming bugs with a precision of 39 percent.

1 Introduction

In statically typed programming languages, method parameters have types to ensure that each argument passed to a method has the expected type. ^1.

When saying method, we mean both functions (as in C) and methods (as in Java). We refer to formal parameters in a method declaration as parameters and to objects passed to methods at a call site as arguments.

Unfortunately, type specifications are useless when a method has multiple parameters of the same type. For example, a method setEndPoints(int high, int low) requires two int arguments. If a programmer accidentally calls this method with incorrectly ordered arguments, the compiler has no means to warn her. Can we support programmers in ordering equally typed arguments correctly?