Extensible type-directed editing

Dependently typed programming languages, such as Idris and Agda, feature rich interactive environments that use informative types to assist users with the construction of programs. However, these environments have been provided by the authors of the language, and users have not had an easy way to extend and customize them. We address this problem by extending Idris's metaprogramming facilities with primitives for describing new type-directed editing features, making Idris's editors as extensible as its elaborator.