SE-0354 (Second Review): Regex Literals

[hamishknight]

@Paul_Cantrell

One reasonable rule — not necessarily advocating, just musing — would be as follows:

1. Remove comments
2. For each line, remove all leading and trailing whitespace
3. Remove newlines
4. Any whitespace that remains is significant

IMO it would be nice to support the ability to use whitespace to aid readability, an example from the proposal:

let regex = #/
  # Match a line of the format e.g "DEBIT  03/03/2022  Totally Legit Shell Corp  $2,000,000.00"
  (?<kind>    \w+)                \s\s+
  (?<date>    \S+)                \s\s+
  (?<account> (?: (?!\s\s) . )+)  \s\s+ # Note that account names may contain spaces.
  (?<amount>  .*)
  /#

That being said, I do agree that the following is surprising:

@Paul_Cantrell

#/hello world/#

matches "hello world"

#/
  hello world
/#

does not match "hello world"

At the very least, if this is the behavior we decide to go with, it seems like we could warn when whitespace is intermixed between literal characters in a regex. For example a b c would raise a warning, but \d \s | [abc] would not. I'm not sure whether we'd want the warning to apply to a character class such as [ a b c ] though (maybe only if there's a single space?).