Highlighting support for FsLex (.fsl) and FsYacc (.fsy) files
The Ionide F# extension should be installed to provide support for highlighting within F# code blocks: https://marketplace.visualstudio.com/items?itemName=Ionide.Ionide-fsharp
Warning: this is almost completely based off the ocamllex and ocamlyacc syntaxes, so there may be inconsistencies between highlighted grammar and what is valid FsLex/FsYacc source code. Please submit an issue if something is off or missing.
Original OCaml extension: https://github.com/hackwaly/vscode-ocaml
Repackaged OCaml extension: https://github.com/mnxn/vscode-ocaml-mll-mly