SE-0350 (second review): Regex Type and Overview

[1-877-547-7272]

@Michael_Ilseman

While this is nice to have, I believe the truly interesting and powerful use cases come with the ability to extract values from the pattern match itself, which is future work and requires language features:

I'd love to see regexes be given the ability to declare constants and variables inline when they're used within a case condition, rather than requiring constants and variables to be declared outside the regex like a value-binding pattern would. For example:

if case /(?<let identifier>[[:alpha:]]\w*) = (?<let hex? = Int($0, radix: 16)>[0-9A-F]+)/ = string {
    print(identifier, hex)
}

IMO this is much clearer, and aligns much better with Chris Lattner's original vision for regular expressions:

@Chris_Lattner

2. I’d like to explore the idea of making // syntax be patterns instead of simply literals. As a pattern, it should be possible to bind submatches directly into variable declarations, eliminating the need to count parens in matches or other gross things. Here is strawman syntax with a dumb example:

if case /([a-zA-Z]+: let firstName) ([a-zA-Z]+: let lastName)/ = getSomeString() {
print(firstName, lastName)
}