State-of-the-art neural models of source code tend to be evaluated on the generation of individual expressions and lines of code, and commonly fail on long-horizon tasks such as the generation of entire method bodies. We propose to address this deficiency using weak supervision from a static program analyzer. Our neurosymbolic method allows a deep generative model to symbolically compute, using calls to a static-analysis tool, long-distance semantic relationships in the code that it has already generated. During training, the model observes these relationships and learns to generate programs conditioned on them. We apply our approach to the problem of generating entire Java methods given the remainder of the class that contains the method. Our experiments show that the approach substantially outperforms state-of-the-art transformers and a model that explicitly tries to learn program semantics on this task, both in terms of producing programs free of basic semantic errors and in terms of syntactically matching the ground truth.

Existing deep models for code tend to be trained on syntactic program representations. We present an alternative, called Neural Attribute Grammars, that exposes the semantics of the target language to the training procedure using an attribute grammar. During training, our model learns to replicate the relationship between the syntactic rules used to construct a program, and the semantic attributes (for example, symbol tables) constructed from the context in which the rules are fired. We implement the approach as a system for conditional generation of Java programs modulo eleven natural requirements. Our experiments show that the system generates constraint-abiding programs with significantly higher frequency than a baseline model trained on syntactic program representations, and also in terms of generation accuracy.