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Add support for optional slice types (#507)

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* 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
This commit is contained in:
Alex Crichton
2018-07-19 14:44:23 -05:00
committed by GitHub
parent 6eef5f7b52
commit cbeb301371
20 changed files with 1214 additions and 725 deletions
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12
src/lib.rs
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@ -61,8 +61,8 @@ pub struct JsValue {
idx: u32,
}
const JSIDX_NULL: u32 = 0;
const JSIDX_UNDEFINED: u32 = 2;
const JSIDX_UNDEFINED: u32 = 0;
const JSIDX_NULL: u32 = 2;
const JSIDX_TRUE: u32 = 4;
const JSIDX_FALSE: u32 = 6;
const JSIDX_RESERVED: u32 = 8;
@ -345,11 +345,8 @@ externs! {
fn __wbindgen_string_new(ptr: *const u8, len: usize) -> u32;
fn __wbindgen_number_new(f: f64) -> u32;
fn __wbindgen_number_get(idx: u32, invalid: *mut u8) -> f64;
fn __wbindgen_null_new() -> u32;
fn __wbindgen_undefined_new() -> u32;
fn __wbindgen_is_null(idx: u32) -> u32;
fn __wbindgen_is_undefined(idx: u32) -> u32;
fn __wbindgen_boolean_new(val: u32) -> u32;
fn __wbindgen_boolean_get(idx: u32) -> u32;
fn __wbindgen_symbol_new(ptr: *const u8, len: usize) -> u32;
fn __wbindgen_is_symbol(idx: u32) -> u32;
@ -673,6 +670,11 @@ pub mod __rt {
#[no_mangle]
pub unsafe extern fn __wbindgen_free(ptr: *mut u8, size: usize) {
// This happens for zero-length slices, and in that case `ptr` is
// likely bogus so don't actually send this to the system allocator
if size == 0 {
return
}
let align = mem::align_of::<usize>();
let layout = Layout::from_size_align_unchecked(size, align);
System.dealloc(ptr, layout);