Reflection in macros

[Jason Pellerin]

I'm pretty sure I'm doing this wrong: http://play.crystal-lang.org/#/r/bqq and reflection of this kind (finding the base generic types of an array of nested arrays) (yes, still trying to make Iterator.flatten work) shouldn't require using regexes to pry apart stringifed type params. But I don't see another way to do this, using the existing type reflection facilities available in macros. What am I missing? Is there a nicer way to do this, or does the macro system maybe need more functions for traversing and introspecting nodes and sets of nodes?

jhp

[Ben Miller]

The ASTNode returned by TypeNode#type_params is an ArrayLiteral(TypeNode), so even though it isn't a "proper" array literal (I got a lot of parse errors while looking at this), we have access to ArrayLiteral#map and ArrayLiteral#argify, so it is possible to at least eliminate the regexes: http://play.crystal-lang.org/#/r/bqy

On Mon, Aug 17, 2015 at 9:25 AM Jason Pellerin <j...@stripe.com> wrote:

I'm pretty sure I'm doing this wrong: http://play.crystal-lang.org/#/r/bqq and reflection of this kind (finding the base generic types of an array of nested arrays) (yes, still trying to make Iterator.flatten work) shouldn't require using regexes to pry apart stringifed type params. But I don't see another way to do this, using the existing type reflection facilities available in macros. What am I missing? Is there a nicer way to do this, or does the macro system maybe need more functions for traversing and introspecting nodes and sets of nodes?

jhp

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[Jason Pellerin]

Ahhh! Interesting, that's much nicer -- though not quite what I want, because it doesn't fully extract the internal types. For the array example it ends up with `(String | Int32 | Array(Int32) | Array(String))` where it should be just `(String|Int32)`. I'll have to dig into it a little. Thank you!

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[Ary Borenszweig]

I wouldn't use macros for that, typeof is much better for this:

http://play.crystal-lang.org/#/r/7td

Check typeof(Array.elem_type(...))

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