In part, that's right. For example, there is an extension called "rank-n" types where global type inference is provably impossible. But even in Haskell 98, type classes often create ambiguities that mean the compiler doesn't know what code to generate, as in the example I gave with

   show (read "1")

You fix these with annotations.

I couldn't say why Ocaml's Emacs mode is so much better. Merlin was a game changer for me, and I've never had issues getting it to work. ghc-mod is the equivalent in Ocaml, but I've never managed to get that to work.

I'm curious what about Ocaml's Emacs mode is better. I use dante for Haskell in Emacs which is good, but I'm always interesting in hearing about better technologies.

I'm not the parent, but thanks for the link to Dante.

One of the main things I like about Ocaml and merlin is how robustly it can tell you the types of expressions by hitting "C-t". It usually works on incomplete code, and it will tell you the type of arbitrary subexpressions (not just identifiers) in your selected region.

It will do automatic destructuring of an identifier (producing a match/case expression with the patterns in the ADTs filled in for you). It's not perfect, but I use it a lot for complex ADTs.

The autocompletion is great too. It will complete for local variables in scope, and it must be having to do some fairly complex stuff in the background, since it'll autocomplete for local modules applied to functors. For example, you can write

   let foo x =
     let open Foo(Bar) in
     ...

and when you autocomplete inside the "...", it will bring in completions from the module generated by applying Bar to Foo.

I'd be interested to hear how dante compares.

Thanks!

> I'd be interested to hear how dante compares.

> it can tell you the types of expressions

dante has flaky support for this

> It will do automatic destructuring of an identifier

dante does support this. It's a bit hokey because the code it inserts doesn't match pre-existing indentation, but it is useful.

> The autocompletion is great too. It will complete for local variables in scope

That sounds very cool. I don't think dante does that, although I've never tried it.

The keybinding (by default), is C-c C-t, btw.