Design for polymorphic IDL types #611
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| @@ -117,6 +117,34 @@ In addition to this basic grammar, a few syntactic shorthands are supported that | |||
| | <name> := <name> : null (only in variants) | |||
| ``` | |||
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| We also support polymorphic type definitions as syntactic shorthands that will be compiled to the basic forms: | |||
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Thinking more about it, maybe we should just support polymorphism in the core grammar, instead of syntactic shorthands. It's up to the codegen for the target language to decide if they want to do monomorphization. If the target language supports polymorphism, the generated binding will be more readable this way.
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It's not that easy. If you wanted to enable dispatching to monomorphised definitions on the callee end then you'd need to provide type information to do that with (the values are not generally enough). So we'd need to do type passing as evidence, and ways to construct/destruct that, which adds a whole layer of complexity (plus enables polymorphism to become non-parametric, which may be undesirable).
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This looks okay as far as syntax goes, but it doesn't fully define semantics. Type constructors introduce extra complexity regarding recursion, since you must ensure that their expansion always terminates. One way to enforce that is by requiring that all recursion is uniform, but that is a somewhat non-trivial check (which is the reason why we haven't even implemented that check in AS yet :) ).
So I'm somewhat hesitant to spend time on this right now, and would rather suggest deferring it until after devnet launch. WDYT?
| @@ -117,6 +117,34 @@ In addition to this basic grammar, a few syntactic shorthands are supported that | |||
| | <name> := <name> : null (only in variants) | |||
| ``` | |||
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| We also support polymorphic type definitions as syntactic shorthands that will be compiled to the basic forms: | |||
There was a problem hiding this comment.
It's not that easy. If you wanted to enable dispatching to monomorphised definitions on the callee end then you'd need to provide type information to do that with (the values are not generally enough). So we'd need to do type passing as evidence, and ways to construct/destruct that, which adds a whole layer of complexity (plus enables polymorphism to become non-parametric, which may be undesirable).
| <typ-args> ::= < <typ>,* > | ||
| ``` | ||
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| Polymorphism is only allowed in the type definitions. `<reftype>` and `<actor>` are always monomorphic. Type definitions are duplicated (monomorphized) to the basic forms according to the different instantiations of `<typ-args>`. For example, the following code |
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To be precise, this isn't polymorphism (type lambdas on the term level), it's type constructors (lambdas on the type level). So I would avoid talking about polymoprhism and monomorphisation. Better call it parameterised type definitions that get expanded.
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Shall we close this until we know we want to go there? |
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Sure, let's close this. Even Rust doesn't need IDL support for polymorphism, so we are good. |
## Changelog for motoko-base: Branch: next-moc Commits: [dfinity/motoko-base@520ccf5d...712d0587](dfinity/motoko-base@520ccf5...712d058) * [`cba05e81`](dfinity/motoko-base@cba05e8) Publish on Mops ([dfinity/motoko-base#618](https://togithub.com/dfinity/motoko-base/issues/618)) * [`d81f5527`](dfinity/motoko-base@d81f552) Add commit hash to `matchers` dependency ([dfinity/motoko-base#621](https://togithub.com/dfinity/motoko-base/issues/621)) * [`c86d76ff`](dfinity/motoko-base@c86d76f) doc: update `List.mo` ([dfinity/motoko-base#616](https://togithub.com/dfinity/motoko-base/issues/616)) * [`4c2a90e7`](dfinity/motoko-base@4c2a90e) Fix compiler warning in `Array.take()` method ([dfinity/motoko-base#611](https://togithub.com/dfinity/motoko-base/issues/611))
## Changelog for motoko-base: Branch: next-moc Commits: [dfinity/motoko-base@520ccf5d...712d0587](dfinity/motoko-base@520ccf5...712d058) * [`cba05e81`](dfinity/motoko-base@cba05e8) Publish on Mops ([dfinity/motoko-base#618](https://togithub.com/dfinity/motoko-base/issues/618)) * [`d81f5527`](dfinity/motoko-base@d81f552) Add commit hash to `matchers` dependency ([dfinity/motoko-base#621](https://togithub.com/dfinity/motoko-base/issues/621)) * [`c86d76ff`](dfinity/motoko-base@c86d76f) doc: update `List.mo` ([dfinity/motoko-base#616](https://togithub.com/dfinity/motoko-base/issues/616)) * [`4c2a90e7`](dfinity/motoko-base@4c2a90e) Fix compiler warning in `Array.take()` method ([dfinity/motoko-base#611](https://togithub.com/dfinity/motoko-base/issues/611))
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