Send-to-interactive of incomplete string leaves FSI waiting for more input

[eiriktsarpalis]

See https://twitter.com/eiriktsarpalis/status/679692748182663168 for a reproduction.

[dsyme]

Please check the F# language spec - string literals in comments are parsed as string literals. This allows for commenting-out of code involving "...*)..." strings and is the same as OCaml

But the true weirdness you're seeing is that sending incomplete strings to F# Interactive causes F# interactive to wait for the completion of the string. I've changed the title to reflect that

[eiriktsarpalis]

I had noticed that the same behaviour occurs in OCaml but I thought this was more of an inherited bug rather than something added by design. It seems very odd! For the record, multi-line comments in the C family of languages don't demonstrate this behaviour (they also don't permit nested comments).

[OmarTawfik]

@dsyme @eiriktsarpalis I'm not following the ask here. FSI waits on incomplete strings until the user ends them (multi-line strings). This is demonstrated by typing:

fsi.exe
"start
end"

Isn't this the expected behavior? shouldn't FSI wait for strings to be terminated?

[dsyme]

I think the ask is that Visual Studio should not send incomplete fragments to the fsi.exe process - it should check the fragments are complete (i.e. expressions or FSI-acceptable declarations) before sending them, and give a meaningful UI error if they are not complete.

[OmarTawfik]

Side note: with the merge of #1582, this should open the door to implementing an interactive window based on Roslyn, which means that we would get colorization, intellisense, and other features in the interactive window for free.