Sound Type-Dependent Syntactic Language Extension

Sound Type-Dependent Syntactic Language Extension

Lorenzen, Florian (Technical University of Berlin)
Erdweg, S.T. (TU Delft Programming Languages; Technische Universität Darmstadt)

2016

Syntactic language extensions can introduce new facilities into a programming language while requiring little implementation effort and modest changes to the compiler. It is typical to desugar language extensions in a distinguished compiler phase after parsing or type checking, not affecting any of the later compiler phases. If desugaring happens before type checking, the desugaring cannot depend on typing information and type errors are reported in terms of the generated code. If desugaring happens after type checking, the code generated by the desugaring is not type checked and may introduce vulnerabilities. Both options are undesirable. We propose a system for syntactic extensibility where desugaring happens after type checking and desugarings are guaranteed to only generate well-typed code. A major novelty of our work is that desugarings operate on typing derivations instead of plain syntax trees. This provides desugarings access to typing information and forms the basis for the soundness guarantee we provide, namely that a desugaring generates a valid typing derivation. We have implemented our system for syntactic extensibility in a language-independent fashion and instantiated it for a substantial subset of Java, including generics and inheritance. We provide a sound Java extension for Scala-like for-comprehensions.

Language extensibility
type soundness
type-dependent desugaring
automatic verification
metaprogramming
macros

http://resolver.tudelft.nl/uuid:237464e9-dbd0-4fa6-a5a9-c2fff227c54d

https://doi.org/10.1145/2837614.2837644

0362-1340

ACM SIGPLAN Notices, 51 (1), 204-216

POPL 2016, 2016-01-20 → 2016-01-23, St. Petersburg, FL, United States

Institutional Repository

journal article

© 2016 Florian Lorenzen, S.T. Erdweg