Implement RFC #2 - casting hierarchy between JS values #640
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alexcrichton
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Wonderful! Thanks @alexcrichton!
Do we want to also add extends = ... attributes to js-sys in this PR, or as a follow up?
src/cast.rs
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| { | ||
| /// Test whether this JS value is an instance of the type `T`. | ||
| /// | ||
| /// This commit performs a dynamic check (at runtime) using the JS |
src/cast.rs
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| /// | ||
| /// This method will return `Err(self)` is `self.is_instance_of::<T>()` | ||
| /// returns `false`, and otherwise it will return `Ok(T)` manufactured with | ||
| /// an unchecked cast (verified safe via the `instanceof` operation). |
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"safe" -> "correct" since we aren't marking unchecked casts as unsafe since it doesn't result in memory unsafety
src/cast.rs
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| /// | ||
| /// This method will return `None` is `self.is_instance_of::<T>()` | ||
| /// returns `false`, and otherwise it will return `Some(&T)` manufactured | ||
| /// with an unchecked cast (verified safe via the `instanceof` operation). |
src/cast.rs
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| /// | ||
| /// This commit performs a dynamic check (at runtime) using the JS | ||
| /// `instanceof` operator. This method returns `self instanceof T`. | ||
| fn is_instance_of<T>(&self) -> bool |
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I imagine we probably want to mark all of these methods as #[inline].
src/cast.rs
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| /// `self` and `T` are simple wrappers around `JsValue`. This method **does | ||
| /// not check whether `self` is an instance of `T`**. If used incorrectly | ||
| /// then this method may cause runtime exceptions in both Rust and JS, this | ||
| /// shoudl be used with caution. |
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Still not fixed in 2 other places.
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Oops thanks, fixed now.
| fn describe() { | ||
| ::wasm_bindgen::JsValue::describe(); | ||
| #[allow(bad_style)] | ||
| const #const_name: () = { |
crates/backend/src/codegen.rs
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| @@ -594,18 +596,63 @@ impl ToTokens for ast::ImportType { | |||
| } | |||
| } | |||
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| // TODO: remove this on the next major version | |||
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Can one mark trait impls as deprecated?
| @@ -168,3 +168,25 @@ possibilities! | |||
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| All of these functions will call `console.log` in JS, but each identifier | |||
| will have only one signature in Rust. | |||
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| * `extends = Bar` - this can be used to say that an imported type extends | |||
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This is going to need to move to guide/src/reference/attributes/on-js-imports/extends.md and a corresponding entry in the SUMMARY.md table of contents
Group all the generated impls in a `const` block so we can use `use` without clashing with the outside scope.
This commit implements the `JsCast` trait automatically for all imported types
in `#[wasm_bindgen] extern { ... }` blocks. The main change here was to generate
an `instanceof` shim for all imported types in case it's needed.
All imported types now also implement `AsRef<JsValue>` and `AsMut<JsValue>`
This commit implements the `extends` attribute for `#[wasm_bindgen]` to statically draw the inheritance hierarchy in the generated bindings, generating appropriate `AsRef`, `AsMut`, and `From` implementations.
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Updated! |
| @@ -0,0 +1,170 @@ | |||
| # Customizing import behavior | |||
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This file got accidentally resurrected.
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Oops, should be dead for real now
This is an implementation of rustwasm/rfcs#2 for the
wasm-bindgensuite of crates. Nothing too too tricky here and the commits inline should explain what they're doing.One question to grapple with is that today we generate
From<JsValue> for ImportedType, but that's not intended from RFC 2, so we'll want to remove it at some point. This PR currently doesn't delete it so we can avoid making a major bump to 0.3, but we may want to go ahead and bump to 0.3 depending on other schedules!