Phrase detection error

[ysalmon]

Description

fsharp-mode does not accurately finds the whole phrase with an if/then/else construct.

Repro steps

Type the follwong, set th text cursoron the closing parenthesis. I used "mark phrase" for the screenshot, but evaluating the phrase gives en F# error error FS0010: Unexpected keyword 'else' in interaction

Expected behavior

I would expect the whole let rec to be considered as the phrase.

Actual behavior

Please provide a description of the actual behaviour you observe.

Known workarounds

Selecting phrase manually and using evaluate region.

Related information

• Operating system Linux
• Branch XUbuntu 16.04
• Emacs version 25
• .NET Runtime, CoreCLR or Mono Version
• Performance information, links to performance testing scripts

[juergenhoetzel]

@ysalmon Should be fixed in master branch: Fix phrase detection error

Can you confirm?

[ysalmon]

Yes it is. Thanks !

[ysalmon]

Well, we are note quite there yet :

[juergenhoetzel]

Confirmed!
This one is harder: Currently fsharp-mode doesn't handle mutual recursive type definitions correctly.

[ysalmon]

Would not a "from ;; to ;;" approach work ? I do not remember how they do it in tuareg, but they surely cannot rely on indentation as it is not meaningful in OCaml.

[juergenhoetzel]

Would not a "from ;; to ;;" approach work ?

Could you elaborate on "from ;; to ;;" approach?

[ysalmon]

When using OCaml in interactive mode (and fsharpi as well I think), you have to append ;; to phrases, so that ocaml knows that it is complete.

It is also customary to append ;; to phrases when typing code in Emacs/tuareg to evaluate them in interactive mode (in earlier versions of Caml, namely Caml Light, ;; was even part of the language). This does not cause any problem because in compilation mode (ocamlc), these ;; are simply ignored.

I do not know if this habit also exists in F#, but it makes it convenient to detect phrases : they are, in practice, the text that lies between two ;;s. So one does not have to reimplement the whole F# syntax analyser in EmacsLisp. The only difficulty is agreeing on what "phrase under the text cursor" means : ocaml/tuareg#158

[juergenhoetzel]

I do not know if this habit also exists in F#, but it makes it convenient to detect phrases : they are, in practice, the text that lies between two ;;s. So one does not have to reimplement the whole F# syntax analyser in EmacsLisp. The only difficulty is agreeing on what "phrase under the text cursor" means : ocaml/tuareg#158

Thanks for the explanation. But this would require Users to use ";; " to explicitly seperate phrases in the Source files?

I consider another workaround: checking if first token in phrase is and and recursively call (fsharp-beginning-of-block) in this case.

[ysalmon]

Yes, but it would also let them control what part of the code should be (re)executed by C-c C-e (maybe several F# statements). tuareg also has an "execute the whole file" command with shortcut C-c C-b.

[juergenhoetzel]

This one is harder: Currently fsharp-mode doesn't handle mutual recursive type definitions correctly.

This should be fixed in master: Handle mutually recursive definitions in phrase detection

Yes, but it would also let them control what part of the code should be (re)executed by C-c C-e (maybe several F# statements). tuareg also has an "execute the whole file" command with shortcut C-c C-b.

In fsharp-mode we already have:

C-c C-f runs the command fsharp-load-buffer-file
C-c C-r runs the command fsharp-eval-region

I definitely see a use-case for your proposed solution. But to be honest, the fsharp-mode indentation/parsing code is not in good shape and could use some help from additional contributors (before adding more features).