Investigate possibilities to parse attributes without reflection

We had a discussion about DrupalCon Lille about this.

One idea was to create an 'attribute registry' - i.e. to essentially parse out all attributes from a file at once and store them somewhere in a format.

That way if a single file contains (or might contain) multiple attributes types that all need to be discovered, we would only check that file once instead of once-per attribute type.

However it would be complex to implement so we thought better to see how we're doing after conversions.

Ideas like checking for #( worth doing first too if they're effective.

Have you looked at https://github.com/olvlvl/composer-attribute-collector?

Move nikic/php-parser up from dev dependency to normal and run something like https://gist.github.com/chx/9f289ffd541701228ba98243dd7eaff7

@mstrelan it uses reflection https://github.com/olvlvl/composer-attribute-collector/blob/a3d45a2e9bab... it just does it when the file gets installed by composer, it would be a very different development workflow compared to what we have now.