“…Recently, GNNs (Hamilton, Ying, and Leskovec 2017;Li et al 2015;Kipf and Welling 2016;Xu et al 2018) have become a hot research topic since their strengths in learning structure data. Various applications in different domains such as chemistry biology (Duvenaud et al 2015), computer vision (Norcliffe-Brown, Vafeias, andParisot 2018), natural language processing (Xu et al 2018;Chen, Wu, and Zaki 2019b) have demonstrated the effectiveness of GNNs. In program scenario, compared with the early works to represent programs with abstract syntax tree (Alon et al 2018(Alon et al , 2019Liu et al 2020b), more works have already attempted to use graphs (Allamanis, Brockschmidt, and Khademi 2017) to learn the semantics for various applications, e.g., source code summarization (Liu et al 2020a;Fernandes, Allamanis, and Brockschmidt 2018), vulnerability detection (Zhou et al 2019), type inference (Allamanis et al 2020).…”