Support expression sequences

[michallepicki]

Describe the bug When combining multiple OCaml expressions with ( expr1 ; expr2 ) or begin expr1 ; expr2 end, the resulting Erlang code is "flattened" and can have different result than expected or not compile at all.

To Reproduce

1. Create a file main.ml containing

   
   let print thing = Io.format "~0tp~n" [ thing ]

let main _ = print ( print "hej" ; true )

or
```ocaml
let print thing = Io.format "~0tp~n" [ thing ]

let main _ =
  print
    begin
      print "hej" ;
      true
    end

2. Run command caramel compile main.ml && escript main.erl
3. See error:

   main.erl:10: function print/2 undefined

This happens because of this incorrect generated Erlang code:

% Source code generated with Caramel.
-module(main).

-export([main/1]).
-export([print/1]).

-spec print(_) -> ok.
print(Thing) -> io:format(<<"~0tp~n">>, [Thing | []]).

-spec main(_) -> ok.
main(_) -> print(print(<<"hej">>),
true).

Expected behavior Erlang gets generated with:

-spec main(_) -> ok.
main(_) -> print(begin print(<<"hej">>), true end).

Environment (please complete the following information):

• OS: Ubuntu Linux 18.04
• Caramel version 0.1
• Erlang version 23.2.2

[michallepicki]

This may be a good point to start: https://github.com/AbstractMachinesLab/caramel/blob/main/caramel/compiler/ocaml_to_erlang/fun.ml#L399

[michallepicki]

I will look into this one

[michallepicki]

With #80 as of e2f88eb we're getting this output:

% Source code generated with Caramel.
-module(main).

-export([main/1]).
-export([print/1]).

-spec print(_) -> ok.
print(Thing) -> io:format(<<"~0tp~n">>, [Thing | []]).

-spec main(_) -> ok.
main(_) -> print(begin
  print(<<"hej">>),
  true
end).

and it runs:

$ caramel compile main.ml
Compiling main.erl      OK
$ escript main.erl
<<"hej">>
true