Update all non-mutable slices into Rust to use AllocCopy

This commit migrates all non-mutable slices incoming into Rust to use
the standard `AllocCopy` binding instead of using a custom `Slice`
binding defined by `wasm-bindgen`. This is done by freeing the memory
from Rust rather than freeing the memory from JS. We can't do this for
mutable slices yet but otherwise this should be working well!

crates/cli-support/src/js/incoming.rs

@@ -153,7 +153,7 @@ impl<'a, 'b> Incoming<'a, 'b> {
 
             // Similar to `AllocCopy`, except that we deallocate in a finally
             // block.
-            NonstandardIncoming::Slice { kind, val, mutable } => {
+            NonstandardIncoming::MutableSlice { kind, val } => {
                 let (expr, ty) = self.standard_typed(val)?;
                 assert_eq!(ty, ast::WebidlScalarType::Any.into());
                 let func = self.cx.pass_to_wasm_function(*kind)?;
@@ -162,7 +162,7 @@ impl<'a, 'b> Incoming<'a, 'b> {
                     .prelude(&format!("const ptr{} = {}({});", i, func, expr));
                 self.js
                     .prelude(&format!("const len{} = WASM_VECTOR_LEN;", i));
-                self.finally_free_slice(&expr, i, *kind, *mutable)?;
+                self.finally_free_slice(&expr, i, *kind, true)?;
                 self.js.typescript_required(kind.js_ty());
                 return Ok(vec![format!("ptr{}", i), format!("len{}", i)]);
             }

crates/cli-support/src/webidl/incoming.rs

@@ -47,15 +47,11 @@ pub enum NonstandardIncoming {
         expr: Box<ast::IncomingBindingExpression>,
     },
 
-    /// JS is passing a typed slice of data into Rust. Currently this is
+    /// A mutable slice of values going from JS to Rust, and after Rust finishes
-    /// implemented with a deallocation in the JS shim, hence a custom binding.
+    /// the JS slice is updated with the current value of the slice.
-    ///
+    MutableSlice {
-    /// TODO: we should move deallocation into Rust so we can use a vanilla and
-    /// standard webidl binding here.
-    Slice {
         kind: VectorKind,
         val: ast::IncomingBindingExpression,
-        mutable: bool,
     },
 
     /// This is either a slice or `undefined` being passed into Rust.
@@ -216,52 +212,11 @@ impl IncomingBuilder {
             Descriptor::Option(d) => self.process_option(d)?,
 
             Descriptor::String | Descriptor::Vector(_) => {
-                use wasm_webidl_bindings::ast::WebidlScalarType::*;
-
                 let kind = arg.vector_kind().ok_or_else(|| {
                     format_err!("unsupported argument type for calling Rust function from JS {:?}", arg)
                 })? ;
                 self.wasm.extend(&[ValType::I32; 2]);
-                match kind {
+                self.alloc_copy_kind(kind)
-                    VectorKind::I8 => self.alloc_copy(Int8Array),
-                    VectorKind::U8 => self.alloc_copy(Uint8Array),
-                    VectorKind::ClampedU8 => self.alloc_copy(Uint8ClampedArray),
-                    VectorKind::I16 => self.alloc_copy(Int16Array),
-                    VectorKind::U16 => self.alloc_copy(Uint16Array),
-                    VectorKind::I32 => self.alloc_copy(Int32Array),
-                    VectorKind::U32 => self.alloc_copy(Uint32Array),
-                    VectorKind::F32 => self.alloc_copy(Float32Array),
-                    VectorKind::F64 => self.alloc_copy(Float64Array),
-                    VectorKind::String => {
-                        let expr = ast::IncomingBindingExpressionAllocUtf8Str {
-                            alloc_func_name: self.alloc_func_name(),
-                            expr: Box::new(self.expr_get()),
-                        };
-                        self.webidl.push(DomString);
-                        self.bindings
-                            .push(NonstandardIncoming::Standard(expr.into()));
-                    }
-                    VectorKind::I64 | VectorKind::U64 => {
-                        let signed = match kind {
-                            VectorKind::I64 => true,
-                            _ => false,
-                        };
-                        self.bindings.push(NonstandardIncoming::AllocCopyInt64 {
-                            alloc_func_name: self.alloc_func_name(),
-                            expr: Box::new(self.expr_get()),
-                            signed,
-                        });
-                        self.webidl.push(Any);
-                    }
-                    VectorKind::Anyref => {
-                        self.bindings
-                            .push(NonstandardIncoming::AllocCopyAnyrefArray {
-                                alloc_func_name: self.alloc_func_name(),
-                                expr: Box::new(self.expr_get()),
-                            });
-                        self.webidl.push(Any);
-                    }
-                }
             }
 
             // Can't be passed from JS to Rust yet
@@ -309,12 +264,15 @@ impl IncomingBuilder {
                     )
                 })?;
                 self.wasm.extend(&[ValType::I32; 2]);
-                self.bindings.push(NonstandardIncoming::Slice {
+                if mutable {
-                    kind,
+                    self.bindings.push(NonstandardIncoming::MutableSlice {
-                    val: self.expr_get(),
+                        kind,
-                    mutable,
+                        val: self.expr_get(),
-                });
+                    });
-                self.webidl.push(ast::WebidlScalarType::Any);
+                    self.webidl.push(ast::WebidlScalarType::Any);
+                } else {
+                    self.alloc_copy_kind(kind)
+                }
             }
             _ => bail!(
                 "unsupported reference argument type for calling Rust function from JS: {:?}",
@@ -445,6 +403,51 @@ impl IncomingBuilder {
         "__wbindgen_malloc".to_string()
     }
 
+    fn alloc_copy_kind(&mut self, kind: VectorKind) {
+        use wasm_webidl_bindings::ast::WebidlScalarType::*;
+
+        match kind {
+            VectorKind::I8 => self.alloc_copy(Int8Array),
+            VectorKind::U8 => self.alloc_copy(Uint8Array),
+            VectorKind::ClampedU8 => self.alloc_copy(Uint8ClampedArray),
+            VectorKind::I16 => self.alloc_copy(Int16Array),
+            VectorKind::U16 => self.alloc_copy(Uint16Array),
+            VectorKind::I32 => self.alloc_copy(Int32Array),
+            VectorKind::U32 => self.alloc_copy(Uint32Array),
+            VectorKind::F32 => self.alloc_copy(Float32Array),
+            VectorKind::F64 => self.alloc_copy(Float64Array),
+            VectorKind::String => {
+                let expr = ast::IncomingBindingExpressionAllocUtf8Str {
+                    alloc_func_name: self.alloc_func_name(),
+                    expr: Box::new(self.expr_get()),
+                };
+                self.webidl.push(DomString);
+                self.bindings
+                    .push(NonstandardIncoming::Standard(expr.into()));
+            }
+            VectorKind::I64 | VectorKind::U64 => {
+                let signed = match kind {
+                    VectorKind::I64 => true,
+                    _ => false,
+                };
+                self.bindings.push(NonstandardIncoming::AllocCopyInt64 {
+                    alloc_func_name: self.alloc_func_name(),
+                    expr: Box::new(self.expr_get()),
+                    signed,
+                });
+                self.webidl.push(Any);
+            }
+            VectorKind::Anyref => {
+                self.bindings
+                    .push(NonstandardIncoming::AllocCopyAnyrefArray {
+                        alloc_func_name: self.alloc_func_name(),
+                        expr: Box::new(self.expr_get()),
+                    });
+                self.webidl.push(Any);
+            }
+        }
+    }
+
     fn alloc_copy(&mut self, webidl: ast::WebidlScalarType) {
         let expr = ast::IncomingBindingExpressionAllocCopy {
             alloc_func_name: self.alloc_func_name(),

src/convert/slices.rs

@@ -94,14 +94,11 @@ macro_rules! vectors {
 
         impl RefFromWasmAbi for [$t] {
             type Abi = WasmSlice;
-            type Anchor = &'static [$t];
+            type Anchor = Box<[$t]>;
 
             #[inline]
-            unsafe fn ref_from_abi(js: WasmSlice) -> &'static [$t] {
+            unsafe fn ref_from_abi(js: WasmSlice) -> Box<[$t]> {
-                slice::from_raw_parts(
+                <Box<[$t]>>::from_abi(js)
-                    <*const $t>::from_abi(js.ptr),
-                    js.len as usize,
-                )
             }
         }
 
@@ -195,11 +192,11 @@ impl<'a> OptionIntoWasmAbi for &'a str {
 
 impl RefFromWasmAbi for str {
     type Abi = <[u8] as RefFromWasmAbi>::Abi;
-    type Anchor = &'static str;
+    type Anchor = Box<str>;
 
     #[inline]
     unsafe fn ref_from_abi(js: Self::Abi) -> Self::Anchor {
-        str::from_utf8_unchecked(<[u8]>::ref_from_abi(js))
+        mem::transmute::<Box<[u8]>, Box<str>>(<Box<[u8]>>::from_abi(js))
     }
 }