oxcaml Updating Merlin After Compiler Frontend Changes
Merlin (external/merlin/) vendors the compiler's frontend. Any frontend change — approximately parsing/, typing/, and the files in file_formats/ and utils/ they use — must be imported into Merlin; a CI check verifies this. Import by running external/merlin/scripts/import-ocaml-source.sh (never hand-merge compiler changes into external/merlin, and never manually modify external/merlin/upstream/ocaml_flambda except for external/merlin/upstream/ocaml_flambda/.gitattributes), then get make merlin-test passing. This is what the user is asking you to do if they say something like "Update Merlin", "Fix Merlin", or "Merge compiler/frontend/typing/type-checker changes into Merlin". New compiler flags (even backend-only ones) also require a Merlin update. Don't do anything before reading the full documentation: external/merlin/HACKING.jst.md.