tree-sitter is the wrong choice here IMHO, because it requires that most languages reimplement their parser in tree-sitter’s DSL, rather than reusing a compiler

tree-sitter is the wrong choice here IMHO, because it requires that most languages reimplement their parser in tree-sitter’s DSL, rather than reusing a compiler's existing parser. A better interface would be a simple binary that produces JSON output from AST, and another binary that produces AST from the same JSON output. Then you'd do a diff on the JSON and converting it to AST before displaying. Then you’d only need to modify the compiler to print out the AST as JSON (and read it in as JSON), instead of reimplementing the parser.