SE-0354: Regex Literals

[xwu (Xiaodi Wu)]

@Paul_Cantrell

Lest it be lost in the din, my original concern was not about paralleling string syntax per se, but about this footgun:

@Paul_Cantrell

#/hello world/#   ✅ matches "hello world"

#/
hello world       ❌ does not match "hello world"
/#

Somebody mentioned upthread the idea of making “ignore whitespace / extended mode” a separate flag, orthogonal to the regex spanning multiple lines. Not sure that makes sense either. (Should a non-extended-mode regex match embedded newlines? What about indentation, then?). Still, perhaps worth a moment of consideration in the post-review followup.

Hold up! I know there were questions about whether whitespace should be non-semantic or not in the various modes, but it had utterly escaped my attention that we have this inconsistency here. Even if whitespaces are semantic in multiline regex literals, one would expect the leading and trailing newlines to be ignored by analogy with string literals. Is this not proposed to be the case? If not, why not?