Alex Crichton cbeb301371 Add support for optional slice types (#507) ... * Shard the `convert.rs` module into sub-modules Hopefully this'll make the organization a little nicer over time! * Start adding support for optional types This commit starts adding support for optional types to wasm-bindgen as arguments/return values to functions. The strategy here is to add two new traits, `OptionIntoWasmAbi` and `OptionFromWasmAbi`. These two traits are used as a blanket impl to implement `IntoWasmAbi` and `FromWasmAbi` for `Option<T>`. Some consequences of this design: * It should be possible to ensure `Option<SomeForeignType>` implements to/from wasm traits. This is because the option-based traits can be implemented for foreign types. * A specialized implementation is possible for all types, so there's no need for `Option<T>` to introduce unnecessary overhead. * Two new traits is a bit unforutnate but I can't currently think of an alternative design that works for the above two constraints, although it doesn't mean one doesn't exist! * The error messages for "can't use this type here" is actually halfway decent because it says these new traits need to be implemented, which provides a good place to document and talk about what's going on here! * Nested references like `Option<&T>` can't implement `FromWasmAbi`. This means that you can't define a function in Rust which takes `Option<&str>`. It may be possible to do this one day but it'll likely require more trait trickery than I'm capable of right now. * Add support for optional slices This commit adds support for optional slice types, things like strings and arrays. The null representation of these has a pointer value of 0, which should never happen in normal Rust. Otherwise the various plumbing is done throughout the tooling to enable these types in all locations. * Fix `takeObject` on global sentinels These don't have a reference count as they're always expected to work, so avoid actually dropping a reference on them. * Remove some no longer needed bindings * Add support for optional anyref types This commit adds support for optional imported class types. Each type imported with `#[wasm_bindgen]` automatically implements the relevant traits and now supports `Option<Foo>` in various argument/return positions. * Fix building without the `std` feature * Actually fix the build... * Add support for optional types to WebIDL Closes #502		2018-07-19 14:44:23 -05:00
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all	Add support for optional slice types (#507)	2018-07-19 14:44:23 -05:00