Add Regular Expression Constants

[magnus-madsen]

• [ ] Add a new Ast.Constant.Regex(java.lang.String) class (after Str).
• [ ] Add a new ParsedAst.Constant.Regex class.
• [ ] Extend the parser to allow the syntax regex"string".
• [ ] In Weeder check that the string is a valid regex (by compiling it with Java).
• [ ] Add a new type constructor Regex.
• [ ] In the Lowering phase replace Ast.Constant.Regex with an InvokeStatic to Pattern.compile.

(Later we can extend the compiler to cache the result of Pattern.compile somewhere.)

[magnus-madsen]

@stephentetley Would you be interested in this? (Otherwise I can ask Jakob.)

[stephentetley]

Thanks Magnus - I'd be open to trying in about two months, but I really need to get my libraries working again with Flix head so that's my immediate priority.

[magnus-madsen]

Of course. Sorry for all the churn. Hopefully the package manager, which arrives soon, will help a bit.

[stephentetley]

I've started looking at this and have gone through the parser and weeder so far.

[mlutze]

Thanks Stephen! Feel free to open a PR while it's in progress.

[stephentetley]

Thanks Matthew, I've just made a WIP PR.

[stephentetley]

The PR now compiles and passes tests: #5707

[magnus-madsen]

Fixed in master.