Modern Integrated Development Environments (IDEs) offer automated refactorings to aid programmers in developing and maintaining software. However, implementing sound automated refactorings is challenging, as refactorings may inadvertently introduce name-binding errors or cause references to resolve to incorrect declarations. To address these issues, previous work by Schäfer et al. proposed replacing concrete references with locked references to separate binding preservation from transformation. Locked references vacuously resolve to a specific declaration, and after transformation must be replaced with concrete references that also resolve to that declaration. Synthesizing these references requires a faithful inverse of the name lookup functions of the underlying language. Manually implementing such inverse lookup functions is challenging due to the complex name-binding features in modern programming languages. Instead, we propose to automatically derive this function from type system specifications written in the Statix meta-DSL. To guide the synthesis of qualified references we use scope graphs , which represent the binding structure of a program, to infer their names and discover their syntactic structure. We evaluate our approach by synthesizing concrete references for locked references in 2528 Java, 196 ChocoPy, and 49 Featherweight Generic Java test programs. Our approach yields a principled languageparametric method for synthesizing references.

Code completion is an editor service in IDEs that proposes code fragments for the user to insert at the caret position in their code. Code completion should be sound and complete. It should be sound, such that it only proposes fragments that do not violate the syntactic and static semantic rules of the language. It should be complete, such that it proposes all valid fragments so that code completion can be used to construct all programs. To realize soundness and completeness, code completion should be informed by the language definition. In practice, the implementation of code completion is an additional effort in the implementation of a language. In this paper, we develop a framework for language-parametric semantic code completion for statically typed programming languages based on their specification of syntax and static semantics, realizing the implementation of a code completion editor service with minimal additional effort. The framework builds on the SDF3 syntax definition formalism and the Statix static semantics specification language. The algorithm reinterprets the static semantics definition to find sound expansions of predicates and solutions to name resolution queries in scope graphs. This allows a search strategy to explore the solution space and synthesize completion proposals. The implementation of the strategy language and code completion algorithm extend the implementation of the Statix solver, and can be used for any language defined in Statix. We demonstrate soundness and completeness of the completion proposal synthesis, and evaluate its performance.

Editor services assist programmers to more effectively write and comprehend code. Implementing editor services correctly is not trivial. This paper focuses on the specification of semantic editor services, those that use the semantic model of a program. The specification of refactorings is a common subject of study, but many other semantic editor services have received little attention. We propose a language-parametric approach to the definition of semantic editor services, using a declarative specification of the static semantics of the programming language, and constraint solving. Editor services are specified as constraint problems, and language specifications are used to ensure correctness. We describe our approach for the following semantic editor services: reference resolution, find usages, goto subclasses, code completion, and the extract definition refactoring. We do this in the context of Statix, a constraint language for the specification of type systems. We investigate the specification of editor services in terms of Statix constraints, and the requirements these impose on a suitable solver.