MerlinTypeOf only displaying types as `'a`, `'b` etc



I’m trying to transition toward Merlin to get type info from my editor (I was happily using ocaml-annot so far, but as non-binary annotations are going to disappear…)

The experience so far is disappointing: most of the time, MerlinTypeOf (which is the only function I really need) only shows type as 'a or 'a -> 'b, etc. unless I point it at an obvious constant in which case it will successfully print int or whatever.
On the same source files with the same annotation (just non-binnary), ocaml-annot is able to properly display the correct type.

I don’t know what’s in a .cmt file but a strings on it suggests that the types are actually present in there as in the .annot file.
Any idea how I could improve things?
I’d like not to maintain a .merlin file if that’s possible.


If you use dune as your build system, it automatically generates .merlin files for you.


Dune won’t build your .merlin file unless you build something. You can either try building some portion of your project, or (I believe) you can call dune build @check in order to get the necessary files for tooling, such as .merlin.


Should I understand that this behavior (not being able to display most types) is caused by the lack of a merlin file? That sounds strange as the whole content required to answer MerlinTypeOf seems to be in the cmt file.