Today, I’m excited to release the next major update to expltools, a bundle that includes the static analysis tool explcheck for the expl3 programming language. This update introduces syntactic analysis, completing three out of five planned processing steps.

What is syntactic analysis?

Syntactic analysis is the stage where TeX tokens identified during lexical analysis (as discussed in my previous blog post) are parsed to recognize expl3 function calls.

For example, consider the following expl3 code snippet:

\tl_new:N
  \l_example_tl
\tl_set:Nn
  { \l_example_tl }
  { foo~bar }

In this snippet, syntactic analysis successfully recognizes two function calls:

1. \tl_new:N \l_example_tl
2. \tl_set:Nn { \l_example_tl } { foo~bar }

Additionally, it issues a warning when an N-type argument like \l_example_tl is unnecessarily wrapped in braces.

What’s next? Semantic analysis

Looking ahead to April, I plan to implement semantic analysis in explcheck. This next step will interpret syntactically identified function calls as higher-level statements. For instance, the above code will be recognized as a variable declaration immediately followed by its definition. Unlike syntactic analysis, which only extracts top-level function calls, semantic analysis will delve deeper—also extracting calls from within function definitions.

This advancement will not only help detect more subtle issues but will also enhance our understanding of expl3 packages. Just as we recently introduced a public website listing issues in the current TeX Live distribution, semantic analysis will pave the way for an online resource that serves as a public library of expl3 symbols available in TeX Live, such as the names of public functions, global variables, and logging messages.

Get involved!

Your feedback is invaluable. Feel free to contribute or share your thoughts by visiting the project repository. Stay tuned for more updates as explcheck continues to evolve!