Implement Type Erasure

[lukewilliamboswell]

zulip discussion

Ayaz's description high level of how it should be implemented

An old WIP PR

example of a program and the corresponding IR

Ayaz offered the following are missing pieces:

• Reference counting. The erased closure layout has a slot for a pointer to a function that performs refcounting on the closure data, but the pointer is never populated right now. some works needs to be done to store a reference to the refcounting function that should be generated, and insert the pointer appropriately. I'm sure this is not that hard to do, but I don't know the details off the top of my head.
• Abilities. This is actually very simple, the main thing is that all the machinery to support abilities with lambda sets (there's a lot of it, if you see anything about "ambient functions" that has to do with it) needs to be skipped. I'm happy to explain what needs to be done to support resolution of abilities in the erasure world when it comes time (I think it's very simple, it's like one new check I believe)
• Some fixes to the mono IR. There are a number of todos related to erased closures that will need to be resolved. One I am aware of is passing closures to higher-order functions by value does not work right now, just because that branch is a TODO.

[smores56]

Quick update: @ayazhafiz has come up with a working MVP experiment of properly working lambda sets, as mentioned here on the Zulip chat. Assuming we are able to translate everything properly, we will likely not need type erasure anymore, as it was intended as a stop-gap for what Ayaz has put together.

[ayazhafiz]

You still need type erasure regardless; it is impossible to implement Task.map2 without it.

…

On Fri, Aug 16, 2024 at 12:00 PM Sam Mohr ***@***.***> wrote: Quick update: @ayazhafiz <https://github.com/ayazhafiz> has come up with a working MVP experiment of properly working lambda sets, as mentioned here on the Zulip chat <https://roc.zulipchat.com/#narrow/stream/395097-compiler-development/topic/lambda.20sets.3A.20compiled/near/462455100>. Assuming we are able to translate everything properly, we will likely not need type erasure anymore, as it was intended as a stop-gap for what Ayaz has put together. — Reply to this email directly, view it on GitHub <#6985 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AE6GL6VSGFEGESV2C6XEJ6LZRYOYTAVCNFSM6AAAAABMNUUZUWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDEOJTG43DINBVGQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>