Better error handling in "str" quasiquoter

[harendra-kumar]

Unterminated interpolation is not detected and reported:

                        [str|sudo #{nixDefaultProfile/bin/usermod
                            -p '*' #{loginId}|]

The above leads to a run time error:

sudo: #{nixDefaultProfile/bin/usermod: command not found

Instead we should report an error ar compile time.

[adithyaov]

Some common mistakes that can be caught:

What one generally wants to do:
x = "Something " ++ here

What one might end up doing:

1. x = "Something #{here}"
2. x = [str|"Something #{here}"|]

Not using str or additional usage of quotes should result in some warnings.

[adithyaov]

Another common mistake,

• [str|Something ${here}|]

# and $ are very close to each other.

[adithyaov]

I use the following in emacs for an easier visual representation,

(highlight-regexp "#{[a-zA-Z0-9_]*}" 'hi-red-b)
(highlight-regexp "\\[str|" 'hi-green-b)
(highlight-regexp "|\\]" 'hi-green-b)

This would highlight

• [|str and |] in bold green.
• The variable #{..} in bold red.