Implement To/FromWasmAbi for arrays

Cargo.toml

@@ -22,7 +22,7 @@ test = false
 [features]
 default = ["spans", "std"]
 spans = ["wasm-bindgen-macro/spans"]
-std = []
+std = ["array-init"]
 serde-serialize = ["serde", "serde_json", "std"]
 nightly = []
 enable-interning = ["std"]
@@ -40,6 +40,7 @@ wasm-bindgen-macro = { path = "crates/macro", version = "=0.2.75" }
 serde = { version = "1.0", optional = true }
 serde_json = { version = "1.0", optional = true }
 cfg-if = "1.0.0"
+array-init = { version = "2.0.0", optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 js-sys = { path = 'crates/js-sys', version = '0.3.52' }

src/convert/slices.rs

@@ -146,6 +146,8 @@ cfg_if! {
 }
 
 if_std! {
+    use std::{hint, iter};
+
     impl<T> IntoWasmAbi for Vec<T> where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
         type Abi = <Box<[T]> as IntoWasmAbi>::Abi;
 
@@ -174,6 +176,39 @@ if_std! {
         fn is_none(abi: &WasmSlice) -> bool { abi.ptr == 0 }
     }
 
+    impl<T, const N: usize> IntoWasmAbi for [T; N] where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
+        type Abi = <Box<[T]> as IntoWasmAbi>::Abi;
+
+        #[inline]
+        fn into_abi(self) -> Self::Abi {
+            <Box<[T]>>::from(self).into_abi()
+        }
+    }
+
+    impl<T, const N: usize> OptionIntoWasmAbi for [T; N] where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
+        #[inline]
+        fn none() -> WasmSlice { null_slice() }
+    }
+
+    impl<T: Default, const N: usize> FromWasmAbi for [T; N] where Box<[T]>: FromWasmAbi<Abi = WasmSlice> {
+        type Abi = <Box<[T]> as FromWasmAbi>::Abi;
+
+        #[inline]
+        unsafe fn from_abi(js: Self::Abi) -> Self {
+            let vec = <Vec<T>>::from(<Box<[T]>>::from_abi(js));
+            let iter = vec.into_iter().chain(iter::repeat_with(T::default));
+            match array_init::from_iter(iter) {
+                Some(arr) => arr,
+                None => hint::unreachable_unchecked(),
+            }
+        }
+    }
+
+    impl<T: Default, const N: usize> OptionFromWasmAbi for [T; N] where Box<[T]>: FromWasmAbi<Abi = WasmSlice> {
+        #[inline]
+        fn is_none(abi: &WasmSlice) -> bool { abi.ptr == 0 }
+    }
+
     impl IntoWasmAbi for String {
         type Abi = <Vec<u8> as IntoWasmAbi>::Abi;
 

src/describe.rs

@@ -155,6 +155,12 @@ if_std! {
             <Box<[T]>>::describe();
         }
     }
+
+    impl<T, const N: usize> WasmDescribe for [T; N] where Box<[T]>: WasmDescribe {
+        fn describe() {
+            <Box<[T]>>::describe();
+        }
+    }
 }
 
 impl<T: WasmDescribe> WasmDescribe for Option<T> {