Improving type error messages for generic java

Nabil El Boustani, Jurriaan Hage

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Since version 1.5, generics (parametric polymorphism) are part of the Java language. However, adding parametric polymorphism to a language that is built on inclusion polymorphism can be confusing to a novice programmer, because the typing rules are suddenly different and, in the case of Generic Java, quite complex. Indeed, the main Java compilers, Eclipse's EJC compiler and Sun's JAVAC, do not even accept the same set of programs. Moreover, experience with these compilers shows that the error messages provided by them leave more than a little to be desired. To alleviate the latter problem, we describe how to adapt the type inference process of Java to obtain better error diagnostics for generic method invocations. The extension has been implemented into the JastAdd extensible Java compiler.
Original languageEnglish
Title of host publicationProceedings of the 2009 ACM SIGPLAN workshop on Partial evaluation and program manipulation
Subtitle of host publicationPEPM '09
PublisherAssociation for Computing Machinery
Number of pages10
ISBN (Print)9781605583273
Publication statusPublished - 19 Jan 2009


  • Compilers
  • Error reporting
  • Java generics
  • Type Checking


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