Structure editors: user-defined type values and type inference

As structure editors have knowledge of an underlying language, they can guarantee that values of built-in or primitive types used in expressions are syntactically correct. In this case, type inference is quite simple and straightforward, however, there is no such support for values of user-defined types. To overcome this shortcoming, we have developed a structure editor for a polymorphic, strongly-typed, class-based object oriented language which exploits a view extension provided by the language's type system. The authors describe this type extension, its support for defining concrete representations for values of user-defined types, and also how type inference is performed by the structure editor.