Add notes for 8/23 GC meeting #1097
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| BT: Ran into this problem for func.bind, which has a synthesized type, we run into the same issue with any type of inference that it creates types that you haven’t written down. It’s because we have this subtyping relationship that we have to declare, if you haven’t written one of the subtypes in the chain, it’s essentially a synthesized type, and how is that type canonicalized? We don’t have to mandate type canonicalization | ||
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| AR: LUBs only work when you have proper lattice in the type system, or at least a semi lattice. For br_table you need GLBs (?) so you would need a full lattice, that’s a severe constraint. There are cases where you can’t synthesize a proper type, there is no principle type that you could synthesize, it’s not clear how you would solve this problem |
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@rossberg, why would br_table need GLBs?
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@tlively, this was a problem we ran into when we introduced reference types and that we could only fix by adding bottom, see my presentation from June 2019: https://github.com/WebAssembly/meetings/blob/main/main/2019/presentations/2019-06-rossberg-reference-types.pdf
FWIW, people keep being surprised by this one, see e.g. this very recent comment.
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
Co-authored-by: Thomas Lively <[email protected]>
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| BT: Ran into this problem for func.bind, which has a synthesized type, we run into the same issue with any type of inference that it creates types that you haven’t written down. It’s because we have this subtyping relationship that we have to declare, if you haven’t written one of the subtypes in the chain, it’s essentially a synthesized type, and how is that type canonicalized? We don’t have to mandate type canonicalization | ||
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| AR: LUBs only work when you have proper lattice in the type system, or at least a semi lattice. For br_table you need GLBs (?) so you would need a full lattice, that’s a severe constraint. There are cases where you can’t synthesize a proper type, there is no principle type that you could synthesize, it’s not clear how you would solve this problem |
There was a problem hiding this comment.
@tlively, this was a problem we ran into when we introduced reference types and that we could only fix by adding bottom, see my presentation from June 2019: https://github.com/WebAssembly/meetings/blob/main/main/2019/presentations/2019-06-rossberg-reference-types.pdf
FWIW, people keep being surprised by this one, see e.g. this very recent comment.
Co-authored-by: Andreas Rossberg <[email protected]>
Co-authored-by: Andreas Rossberg <[email protected]>
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