Implemented transform-regexp-constructors plugin

[shinew]

Changes RegExp constructors to literals.

[kangax]

This looks great!

I just think that we might miss out on a lot of cases where strings are concatenated together — new RegExp('foo' + 'bar') or where RegExp receieves an identifer (new RegExp(RE_FOO_BAR)) or a combination of two (new RegExp(reSmth + '$')).

Can we try to account for these cases too?

[shinew]

Updated. Also, for RegExp constructors with 0 arguments, this would currently throw at const pattern = evals[0].value;. Catching this case at pseudo-compile time is not terrible, but should this behavior be changed/documented?

[kangax]

Yeah, let's definitely add a check for 0 arguments. It should transform to /(?:)/ (empty non-capturing group). Also, I would rename evals to evaluatedArgs for clarity.

[shinew]

Updated to gracefully handle empty RegExp constructions.

[kangax]

Thanks!

[kangax]

@hzoo @loganfsmyth @danez do we want to also update babili preset?

[hzoo]

yeah if want to add it now - we'll need the package.json for this package + adding it to the preset package.json if we do

[kangax]

@shinew Let's do it. That way we could also see the impact of this plugin on performance with our benchmark.