[Emacs] syntax highlighting improvements

[fsharp]

[Emacs] syntax highlighting improvements

[rneatherway]

Noticed that a string such as @"hello" isn't highlighted properly. Need to be aware that '@' prevents escaping.

[rneatherway]

Further, the single character '"' confuses matters.

[rneatherway]

A (/ incorrectly opens a multiline comment, like (*, and it can't be closed.

[rneatherway]

Simple examples of the main known issues:

// Example of typeof not highlighted
let x (y: 'a) = typeof<'a>

// Example of raw string highlighted badly
let mystring = @"hello \"

// " // Terminate string

// Example of character " highlighted badly
let mychar = '"'

// " // Terminate string

// Example of triple-quoted string highlighted badly
let mystring2 = """ hello " """

// " // Terminate string

// Example of backtick-quoted definition highlighted badly
let ``this is a definition`` () = 1

// Example of class arguments staring with a '/' causing multiline comment
type T (//
         x: int) =
  let f y = x 

// Example of string in a comment causing it not to be highlighted as a comment
// This "should" be a comment

[finalpatch]

I think the general rule is to highlight types, functions and variables where they are declared (not where they are referenced). This is how Emacs CC-Mode works, it makes sense to me, and is easier to implement. In this sense probably typeof('T) should not be highlighted, because this is not creating a type but referencing an existing type.

[rneatherway]

This seems like a reasonable point of view to take re typeof. The string quoting problems are the main thing in that case.

Replying also to https://github.com/rneatherway/fsharpbinding/pull/1#issuecomment-12635767 (let's continue discussion here):

I noticed that the .>>? problems are transient depending on whether or not that code is followed by another definition. Regarding fsi, I think you are right and we should probably turn off highlighting there as it is quite fragile.

[finalpatch]

Like I have said the "? spaces" thing is caused by these lines
;labels (and open)
;;
'("<(assert|open|include|module|namespace|extern|void)>|[~?][
(][a-z][a-zA-Z0-9']_"
;; . font-lock-variable-name-face)

I don't understand why sequences start with ? or ~ should be highlighted.
If you just want to fix this case you could simply remove the "?" in the
above regexp.

To me the biggest problem is the indenting engine. It doesn't work very
well in pattern match expressions (the next line must be indented to the
right of the "match"). eg.
let doAdd (args : list) =
args
|>List.fold (fun acc x -> match x with
| INT n -> acc + n
| _ -> failwith ("can only add INTs")) 0
|> INT
in this example, the patterns inside the lambda function has to be manually
aligned to the previous line. The indenting engine cannot handle it.

Another indenting problem is in computation expressions (such async
workflows). It simply doesn't work inside {}. This is quite annoying
because computation expression is a very important part of the F# language.

Fixing these problems requires a lot more elisp skill than tweaking regexps
and therefore has exceeded my knowledge.

On Thu, Jan 24, 2013 at 9:55 PM, Robin Neatherway
[email protected]:

This seems like a reasonable point of view to take re typeof. The string
quoting problems are the main thing in that case.

Replying also to rneatherway#1https://github.com/rneatherway/fsharpbinding/issues/1#issuecomment-12635767(let's continue discussion here):

I noticed that the .>>? problems are transient depending on whether or
not that code is followed by another definition. Regarding fsi, I think you
are right and we should probably turn off highlighting there as it is quite
fragile.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/70#issuecomment-12646250.

Feng Li

[rneatherway]

Yes I see the same problem. It is quite a large chunk of elisp so I haven't braved it yet either.

I might be hijacking this issue thread, but: I noticed an issue with multi-line strings. The following does not get highlighted:

let x = "btx a
abc" 

It seems the space after btx causes the error, if no space is there, highlighting works fine. I think it has to do with fsharp-mode-indent.el:119 but I don't know how to fix this with regex.

[rneatherway]

Thanks for the report. We should get to this sometime, but I still haven't found time to dig into that section of the code.

Based on below comment, removed additional issue, will create separate issue.

[knocte]

Please create one github issue per problem, do NOT report many problems in the same github issue.

[rneatherway]

Fixed by #292

[rneatherway]

I found another bad example if there are keywords inside a namespace:

open Microsoft.FSharp.Compiler.AbstractIL.Internal

[rneatherway]

Keyword highlighting should be case sensitive.

[rneatherway]

Closed by #496