From 576d940fe1fb22120fa1fc9bae7daa4400fa1fa2 Mon Sep 17 00:00:00 2001
From: Jules Bertholet <jules.bertholet@gmail.com>
Date: Tue, 13 Jul 2021 20:18:01 +0200
Subject: [PATCH 1/2] Implement To/FromWasmAbi for arrays

---
 src/convert/slices.rs | 34 ++++++++++++++++++++++++++++++++++
 src/describe.rs       |  6 ++++++
 2 files changed, 40 insertions(+)

diff --git a/src/convert/slices.rs b/src/convert/slices.rs
index 9d0970f4e6a..5286685882e 100644
--- a/src/convert/slices.rs
+++ b/src/convert/slices.rs
@@ -146,6 +146,8 @@ cfg_if! {
 }
 
 if_std! {
+    use std::convert::TryFrom;
+
     impl<T> IntoWasmAbi for Vec<T> where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
         type Abi = <Box<[T]> as IntoWasmAbi>::Abi;
 
@@ -174,6 +176,38 @@ 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, 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 result = <[T; N]>::try_from(<Vec<T>>::from(<Box<[T]>>::from_abi(js)));
+            return match result {
+                Ok(arr) => arr,
+                Err(_) => panic!("JS array length does not match Rust array")
+            }
+        }
+    }
+
+    impl<T, 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;
 
diff --git a/src/describe.rs b/src/describe.rs
index 2d424f8f3f7..29c4a475f16 100644
--- a/src/describe.rs
+++ b/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> {

From 90c4c0c5487e58fda72ab68c939836613c884e57 Mon Sep 17 00:00:00 2001
From: Jules Bertholet <jules.bertholet@gmail.com>
Date: Wed, 14 Jul 2021 19:00:28 +0200
Subject: [PATCH 2/2] Document #2614

---
 guide/src/reference/types/boxed-jsvalue-slice.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/guide/src/reference/types/boxed-jsvalue-slice.md b/guide/src/reference/types/boxed-jsvalue-slice.md
index c349ad15abc..8060d194a7c 100644
--- a/guide/src/reference/types/boxed-jsvalue-slice.md
+++ b/guide/src/reference/types/boxed-jsvalue-slice.md
@@ -4,6 +4,8 @@
 |:---:|:---:|:---:|:---:|:---:|:---:|:---:|
 | Yes | No | No | Yes | Yes | Yes | A JavaScript `Array` object |
 
+Boxed slices of imported JS types and exported Rust types are also supported. `Vec<T>` is supported wherever `Box<[T]>` is.
+
 ## Example Rust Usage
 
 ```rust