Heregex Comment

Fixes #5428

This fix is simple enough but it causes a substantial change in behavior for Heregexes.

`#` inside of a character class shouldn't be considered a comment. By treating `#`
without whitespace in front as non-comments we could have slight compatability with
Python.

There are other places in the CoffeeScript source where people avoided escaping the `#`
by keeping it next to non-whitespace characters even outside of a character class. This
is different than how Python does it and is probably a bug but maybe it is too late with
the de facto CoffeeScript2 behavior.

I'm not sure if this should be merged in since it changes the behavior quite a lot. Maybe
another one for the CoffeeScript3/Civet bucket.

Refs
---
Python Docs: https://docs.python.org/3/library/re.html#re.X

Author: STRd6

docs/v2/browser-compiler-legacy/coffeescript.js

@@ -1341,10 +1341,10 @@ HERE_JSTOKEN = ///^ ```     ((?: [^`\\] | \\[\s\S] | `(?!``) )*) ``` ///
 # String-matching-regexes.
 STRING_START   = /^(?:'''|"""|'|")/
 
-STRING_SINGLE  = /// ^(?: [^\\']  | \\[\s\S]                      )* ///
-STRING_DOUBLE  = /// ^(?: [^\\"#] | \\[\s\S] |           \#(?!\{) )* ///
-HEREDOC_SINGLE = /// ^(?: [^\\']  | \\[\s\S] | '(?!'')            )* ///
-HEREDOC_DOUBLE = /// ^(?: [^\\"#] | \\[\s\S] | "(?!"") | \#(?!\{) )* ///
+STRING_SINGLE  = /// ^(?: [^\\']   | \\[\s\S]                      )* ///
+STRING_DOUBLE  = /// ^(?: [^\\"\#] | \\[\s\S] |           \#(?!\{) )* ///
+HEREDOC_SINGLE = /// ^(?: [^\\']   | \\[\s\S] | '(?!'')            )* ///
+HEREDOC_DOUBLE = /// ^(?: [^\\"\#] | \\[\s\S] | "(?!"") | \#(?!\{) )* ///
 
 INSIDE_JSX = /// ^(?:
     [^
@@ -1376,19 +1376,19 @@ VALID_FLAGS  = /^(?!.*(.).*\1)[gimsuy]*$/
 HEREGEX      = /// ^
   (?:
       # Match any character, except those that need special handling below.
-      [^\\/#\s]
+      [^\\/\#\s]
       # Match `\` followed by any character.
     | \\[\s\S]
       # Match any `/` except `///`.
     | /(?!//)
       # Match `#` which is not part of interpolation, e.g. `#{}`.
     | \#(?!\{)
       # Comments consume everything until the end of the line, including `///`.
-    | \s+(?:#(?!\{).*)?
+    | \s*(?:\#(?!\{).*)?
   )*
 ///
 
-HEREGEX_COMMENT = /(\s+)(#(?!{).*)/gm
+HEREGEX_COMMENT = /(\s*)(#(?!{).*)/gm
 
 REGEX_ILLEGAL = /// ^ ( / | /{3}\s*) (\*) ///
 

docs/v2/browser-compiler-modern/coffeescript.js

@@ -5783,7 +5783,7 @@ STRING_OMIT    = ///
 HEREGEX_OMIT = ///
     ((?:\\\\)+)     # Consume (and preserve) an even number of backslashes.
   | \\(\s)          # Preserve escaped whitespace.
-  | \s+(?:#.*)?     # Remove whitespace and comments.
+  | \s+(?:\#.*)?     # Remove whitespace and comments.
 ///g
 
 # Helper Functions