Merge pull request #702 from alexcrichton/dictionaries

Implement support for WebIDL dictionaries

crates/backend/src/ast.rs

@@ -21,6 +21,10 @@ pub struct Program {
     pub consts: Vec<Const>,
     /// rust submodules
     pub modules: Vec<Module>,
+    /// "dictionaries", generated for WebIDL, which are basically just "typed
+    /// objects" in the sense that they represent a JS object with a particular
+    /// shape in JIT parlance.
+    pub dictionaries: Vec<Dictionary>,
 }
 
 /// A rust to js interface. Allows interaction with rust objects/functions
@@ -253,6 +257,21 @@ pub struct Module {
     pub imports: Vec<Import>,
 }
 
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+#[derive(Clone)]
+pub struct Dictionary {
+    pub name: Ident,
+    pub fields: Vec<DictionaryField>,
+}
+
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+#[derive(Clone)]
+pub struct DictionaryField {
+    pub name: Ident,
+    pub required: bool,
+    pub ty: syn::Type,
+}
+
 impl Program {
     pub(crate) fn shared(&self) -> Result<shared::Program, Diagnostic> {
         Ok(shared::Program {

crates/backend/src/codegen.rs

@@ -74,6 +74,9 @@ impl TryToTokens for ast::Program {
                 errors.push(e);
             }
         }
+        for d in self.dictionaries.iter() {
+            d.to_tokens(tokens);
+        }
 
         Diagnostic::from_vec(errors)?;
 
@@ -1135,6 +1138,153 @@ impl<'a> TryToTokens for ast::Module {
     }
 }
 
+impl ToTokens for ast::Dictionary {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let name = &self.name;
+        let mut methods = TokenStream::new();
+        for field in self.fields.iter() {
+            field.to_tokens(&mut methods);
+        }
+        let required_names = &self.fields.iter()
+            .filter(|f| f.required)
+            .map(|f| &f.name)
+            .collect::<Vec<_>>();
+        let required_types = &self.fields.iter()
+            .filter(|f| f.required)
+            .map(|f| &f.ty)
+            .collect::<Vec<_>>();
+        let required_names2 = required_names;
+        let required_names3 = required_names;
+
+        let const_name = Ident::new(&format!("_CONST_{}", name), Span::call_site());
+        (quote! {
+            #[derive(Clone, Debug)]
+            #[repr(transparent)]
+            pub struct #name {
+                obj: ::js_sys::Object,
+            }
+
+            impl #name {
+                pub fn new(#(#required_names: #required_types),*) -> #name {
+                    let mut _ret = #name { obj: ::js_sys::Object::new() };
+                    #(_ret.#required_names2(#required_names3);)*
+                    return _ret
+                }
+
+                #methods
+            }
+
+            #[allow(bad_style)]
+            const #const_name: () = {
+                use js_sys::Object;
+                use wasm_bindgen::describe::WasmDescribe;
+                use wasm_bindgen::convert::*;
+                use wasm_bindgen::{JsValue, JsCast};
+                use wasm_bindgen::__rt::core::mem::ManuallyDrop;
+
+                // interop w/ JsValue
+                impl From<#name> for JsValue {
+                    fn from(val: #name) -> JsValue {
+                        val.obj.into()
+                    }
+                }
+                impl AsRef<JsValue> for #name {
+                    fn as_ref(&self) -> &JsValue { self.obj.as_ref() }
+                }
+                impl AsMut<JsValue> for #name {
+                    fn as_mut(&mut self) -> &mut JsValue { self.obj.as_mut() }
+                }
+
+                // Boundary conversion impls
+                impl WasmDescribe for #name {
+                    fn describe() {
+                        Object::describe();
+                    }
+                }
+
+                impl IntoWasmAbi for #name {
+                    type Abi = <Object as IntoWasmAbi>::Abi;
+                    fn into_abi(self, extra: &mut Stack) -> Self::Abi {
+                        self.obj.into_abi(extra)
+                    }
+                }
+
+                impl<'a> IntoWasmAbi for &'a #name {
+                    type Abi = <&'a Object as IntoWasmAbi>::Abi;
+                    fn into_abi(self, extra: &mut Stack) -> Self::Abi {
+                        (&self.obj).into_abi(extra)
+                    }
+                }
+
+                impl FromWasmAbi for #name {
+                    type Abi = <Object as FromWasmAbi>::Abi;
+                    unsafe fn from_abi(abi: Self::Abi, extra: &mut Stack) -> Self {
+                        #name { obj: Object::from_abi(abi, extra) }
+                    }
+                }
+
+                impl OptionIntoWasmAbi for #name {
+                    fn none() -> Self::Abi { Object::none() }
+                }
+                impl<'a> OptionIntoWasmAbi for &'a #name {
+                    fn none() -> Self::Abi { <&'a Object>::none() }
+                }
+                impl OptionFromWasmAbi for #name {
+                    fn is_none(abi: &Self::Abi) -> bool { Object::is_none(abi) }
+                }
+
+                impl RefFromWasmAbi for #name {
+                    type Abi = <Object as RefFromWasmAbi>::Abi;
+                    type Anchor = ManuallyDrop<#name>;
+
+                    unsafe fn ref_from_abi(js: Self::Abi, extra: &mut Stack) -> Self::Anchor {
+                        let tmp = <Object as RefFromWasmAbi>::ref_from_abi(js, extra);
+                        ManuallyDrop::new(#name {
+                            obj: ManuallyDrop::into_inner(tmp),
+                        })
+                    }
+                }
+
+                impl JsCast for #name {
+                    fn instanceof(val: &JsValue) -> bool {
+                        Object::instanceof(val)
+                    }
+
+                    fn unchecked_from_js(val: JsValue) -> Self {
+                        #name { obj: Object::unchecked_from_js(val) }
+                    }
+
+                    fn unchecked_from_js_ref(val: &JsValue) -> &Self {
+                        unsafe { &*(val as *const JsValue as *const #name) }
+                    }
+
+                    fn unchecked_from_js_mut(val: &mut JsValue) -> &mut Self {
+                        unsafe { &mut *(val as *mut JsValue as *mut #name) }
+                    }
+                }
+            };
+        }).to_tokens(tokens);
+    }
+}
+
+impl ToTokens for ast::DictionaryField {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let name = &self.name;
+        let ty = &self.ty;
+        (quote! {
+            pub fn #name(&mut self, val: #ty) -> &mut Self {
+                use wasm_bindgen::JsValue;
+                ::js_sys::Reflect::set(
+                    self.obj.as_ref(),
+                    &JsValue::from(stringify!(#name)),
+                    &JsValue::from(val),
+                );
+                self
+            }
+        }).to_tokens(tokens);
+    }
+}
+
 /// Emits the necessary glue tokens for "descriptor", generating an appropriate
 /// symbol name as well as attributes around the descriptor function itself.
 struct Descriptor<'a, T>(&'a Ident, T);

crates/backend/src/defined.rs

@@ -84,6 +84,7 @@ impl ImportedTypes for ast::Program {
     {
         self.imports.imported_types(f);
         self.consts.imported_types(f);
+        self.dictionaries.imported_types(f);
     }
 }
 
@@ -298,21 +299,44 @@ impl ImportedTypes for ast::Const {
     }
 }
 
+impl ImportedTypes for ast::Dictionary {
+    fn imported_types<F>(&self, f: &mut F)
+    where
+        F: FnMut(&Ident, ImportedTypeKind),
+    {
+        f(&self.name, ImportedTypeKind::Definition);
+        for field in self.fields.iter() {
+            field.imported_types(f);
+        }
+    }
+}
+
+impl ImportedTypes for ast::DictionaryField {
+    fn imported_types<F>(&self, f: &mut F)
+    where
+        F: FnMut(&Ident, ImportedTypeKind),
+    {
+        self.ty.imported_types(f);
+    }
+}
+
 /// Remove any methods, statics, &c, that reference types that are *not*
 /// defined.
 pub trait RemoveUndefinedImports {
-    fn remove_undefined_imports<F>(&mut self, is_defined: &F)
+    fn remove_undefined_imports<F>(&mut self, is_defined: &F) -> bool
     where
         F: Fn(&Ident) -> bool;
 }
 
 impl RemoveUndefinedImports for ast::Program {
-    fn remove_undefined_imports<F>(&mut self, is_defined: &F)
+    fn remove_undefined_imports<F>(&mut self, is_defined: &F) -> bool
     where
         F: Fn(&Ident) -> bool,
     {
-        self.imports.remove_undefined_imports(is_defined);
-        self.consts.remove_undefined_imports(is_defined);
+        let a = self.imports.remove_undefined_imports(is_defined);
+        let b = self.consts.remove_undefined_imports(is_defined);
+        let c = self.dictionaries.remove_undefined_imports(is_defined);
+        a || b || c
     }
 }
 
@@ -320,10 +344,11 @@ impl<T> RemoveUndefinedImports for Vec<T>
 where
     T: ImportedTypeReferences,
 {
-    fn remove_undefined_imports<F>(&mut self, is_defined: &F)
+    fn remove_undefined_imports<F>(&mut self, is_defined: &F) -> bool
     where
         F: Fn(&Ident) -> bool,
     {
+        let before = self.len();
         self.retain(|x| {
             let mut all_defined = true;
             x.imported_type_references(&mut |id| {
@@ -336,5 +361,6 @@ where
             });
             all_defined
         });
+        before != self.len()
     }
 }

crates/webidl-tests/Cargo.toml

@@ -10,6 +10,7 @@ path = 'lib.rs'
 
 [build-dependencies]
 wasm-bindgen-webidl = { path = '../webidl' }
+env_logger = "0.5"
 
 [dev-dependencies]
 js-sys = { path = '../js-sys' }
@@ -19,4 +20,3 @@ wasm-bindgen-test = { path = '../test' }
 [[test]]
 name = 'wasm'
 path = 'main.rs'
-

crates/webidl-tests/build.rs

@@ -1,4 +1,5 @@
 extern crate wasm_bindgen_webidl;
+extern crate env_logger;
 
 use std::env;
 use std::fs;
@@ -6,6 +7,7 @@ use std::path::PathBuf;
 use std::process::Command;
 
 fn main() {
+    env_logger::init();
     let idls = fs::read_dir(".")
         .unwrap()
         .map(|f| f.unwrap().path())

crates/webidl-tests/dictionary.js

@@ -0,0 +1,22 @@
+const assert = require('assert');
+
+global.assert_dict_c = function(c) {
+  assert.strictEqual(c.a, 1);
+  assert.strictEqual(c.b, 2);
+  assert.strictEqual(c.c, 3);
+  assert.strictEqual(c.d, 4);
+  assert.strictEqual(c.e, 5);
+  assert.strictEqual(c.f, 6);
+  assert.strictEqual(c.g, 7);
+  assert.strictEqual(c.h, 8);
+};
+
+global.mk_dict_a = function() {
+  return {};
+};
+
+global.assert_dict_required = function(c) {
+  assert.strictEqual(c.a, 3);
+  assert.strictEqual(c.b, "a");
+  assert.strictEqual(c.c, 4);
+};

crates/webidl-tests/dictionary.rs

@@ -0,0 +1,54 @@
+use wasm_bindgen_test::*;
+use wasm_bindgen::prelude::*;
+
+include!(concat!(env!("OUT_DIR"), "/dictionary.rs"));
+
+#[wasm_bindgen]
+extern {
+    fn assert_dict_c(c: &C);
+    #[wasm_bindgen(js_name = assert_dict_c)]
+    fn assert_dict_c2(c: C);
+    #[wasm_bindgen(js_name = assert_dict_c)]
+    fn assert_dict_c3(c: Option<&C>);
+    #[wasm_bindgen(js_name = assert_dict_c)]
+    fn assert_dict_c4(c: Option<C>);
+    fn mk_dict_a() -> A;
+    #[wasm_bindgen(js_name = mk_dict_a)]
+    fn mk_dict_a2() -> Option<A>;
+    fn assert_dict_required(r: &Required);
+}
+
+#[wasm_bindgen_test]
+fn smoke() {
+    A::new().c(1).g(2).h(3).d(4);
+    B::new().c(1).g(2).h(3).d(4).a(5).b(6);
+
+    let mut c = C::new();
+    c.a(1).b(2).c(3).d(4).e(5).f(6).g(7).h(8);
+    assert_dict_c(&c);
+    assert_dict_c2(c.clone());
+    assert_dict_c3(Some(&c));
+    assert_dict_c4(Some(c));
+}
+
+#[wasm_bindgen_test]
+fn get_dict() {
+    mk_dict_a();
+    assert!(mk_dict_a2().is_some());
+}
+
+#[wasm_bindgen_test]
+fn casing() {
+    CamelCaseMe::new().snake_case_me(3);
+}
+
+#[wasm_bindgen_test]
+fn many_types() {
+    ManyTypes::new()
+        .a("a");
+}
+
+#[wasm_bindgen_test]
+fn required() {
+    assert_dict_required(Required::new(3, "a").c(4));
+}

crates/webidl-tests/dictionary.webidl

@@ -0,0 +1,47 @@
+// example from https://heycam.github.io/webidl/#idl-dictionaries
+dictionary B : A {
+  long b;
+  long a;
+};
+
+dictionary A {
+  long c;
+  long g;
+};
+
+dictionary C : B {
+  long e;
+  long f;
+};
+
+partial dictionary A {
+  long h;
+  long d;
+};
+
+// case needs changing
+dictionary camel_case_me {
+  long snakeCaseMe;
+};
+
+dictionary ManyTypes {
+  DOMString a;
+  octet n1;
+  byte n2;
+  unsigned short n3;
+  short n4;
+  unsigned long n5;
+  long n6;
+  // TODO: needs fixing
+  // OtherDict c;
+};
+
+dictionary OtherDict {
+  long a;
+};
+
+dictionary Required {
+  required DOMString b;
+  required long a;
+  long c;
+};

crates/webidl-tests/main.rs

@@ -11,3 +11,4 @@ pub mod enums;
 pub mod namespace;
 pub mod simple;
 pub mod throws;
+pub mod dictionary;

crates/webidl/src/first_pass.rs

@@ -9,6 +9,7 @@
 
 use std::collections::{BTreeMap, BTreeSet};
 
+use weedle::{DictionaryDefinition, PartialDictionaryDefinition};
 use weedle::argument::Argument;
 use weedle::attribute::ExtendedAttribute;
 use weedle::interface::{StringifierOrStatic, Special};
@@ -24,13 +25,13 @@ use util::camel_case_ident;
 #[derive(Default)]
 pub(crate) struct FirstPassRecord<'src> {
     pub(crate) interfaces: BTreeMap<&'src str, InterfaceData<'src>>,
-    pub(crate) dictionaries: BTreeSet<&'src str>,
     pub(crate) enums: BTreeSet<&'src str>,
     /// The mixins, mapping their name to the webidl ast node for the mixin.
     pub(crate) mixins: BTreeMap<&'src str, MixinData<'src>>,
     pub(crate) typedefs: BTreeMap<&'src str, &'src weedle::types::Type<'src>>,
     pub(crate) namespaces: BTreeMap<&'src str, NamespaceData<'src>>,
     pub(crate) includes: BTreeMap<&'src str, BTreeSet<&'src str>>,
+    pub(crate) dictionaries: BTreeMap<&'src str, DictionaryData<'src>>,
 }
 
 /// We need to collect interface data during the first pass, to be used later.
@@ -61,6 +62,13 @@ pub(crate) struct NamespaceData<'src> {
     pub(crate) operations: BTreeMap<OperationId<'src>, OperationData<'src>>,
 }
 
+#[derive(Default)]
+pub(crate) struct DictionaryData<'src> {
+    /// Whether only partial namespaces were encountered
+    pub(crate) partials: Vec<&'src PartialDictionaryDefinition<'src>>,
+    pub(crate) definition: Option<&'src DictionaryDefinition<'src>>,
+}
+
 #[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone, Copy)]
 pub(crate) enum OperationId<'src> {
     Constructor,
@@ -99,6 +107,7 @@ impl<'src> FirstPass<'src, ()> for weedle::Definition<'src> {
 
         match self {
             Dictionary(dictionary) => dictionary.first_pass(record, ()),
+            PartialDictionary(dictionary) => dictionary.first_pass(record, ()),
             Enum(enum_) => enum_.first_pass(record, ()),
             IncludesStatement(includes) => includes.first_pass(record, ()),
             Interface(interface) => interface.first_pass(record, ()),
@@ -118,14 +127,19 @@ impl<'src> FirstPass<'src, ()> for weedle::Definition<'src> {
 
 impl<'src> FirstPass<'src, ()> for weedle::DictionaryDefinition<'src> {
     fn first_pass(&'src self, record: &mut FirstPassRecord<'src>, (): ()) -> Result<()> {
-        if util::is_chrome_only(&self.attributes) {
-            return Ok(());
-        }
-
-        if !record.dictionaries.insert(self.identifier.0) {
-            info!("Encountered multiple dictionary declarations: {}", self.identifier.0);
+        record.dictionaries.entry(self.identifier.0)
+            .or_default()
+            .definition = Some(self);
+        Ok(())
     }
+}
 
+impl<'src> FirstPass<'src, ()> for weedle::PartialDictionaryDefinition<'src> {
+    fn first_pass(&'src self, record: &mut FirstPassRecord<'src>, (): ()) -> Result<()> {
+        record.dictionaries.entry(self.identifier.0)
+            .or_default()
+            .partials
+            .push(self);
         Ok(())
     }
 }
@@ -153,7 +167,7 @@ impl<'src> FirstPass<'src, ()> for weedle::IncludesStatementDefinition<'src> {
         record
             .includes
             .entry(self.lhs_identifier.0)
-            .or_insert_with(Default::default)
+            .or_default()
             .insert(self.rhs_identifier.0);
 
         Ok(())
@@ -372,7 +386,7 @@ impl<'src> FirstPass<'src, ()> for weedle::InterfaceMixinDefinition<'src>{
             let mixin_data = record
                 .mixins
                 .entry(self.identifier.0)
-                .or_insert_with(Default::default);
+                .or_default();
             mixin_data.partial = false;
             mixin_data.members.extend(&self.members.body);
         }

crates/webidl/src/idl_type.rs

@@ -285,7 +285,7 @@ impl<'a> ToIdlType<'a> for Identifier<'a> {
             idl_type.to_idl_type(record)
         } else if record.interfaces.contains_key(self.0) {
             Some(IdlType::Interface(self.0))
-        } else if record.dictionaries.contains(self.0) {
+        } else if record.dictionaries.contains_key(self.0) {
             Some(IdlType::Dictionary(self.0))
         } else if record.enums.contains(self.0) {
             Some(IdlType::Enum(self.0))
@@ -467,7 +467,8 @@ impl<'a> IdlType<'a> {
             IdlType::Float32Array => Some(array("f32", pos)),
             IdlType::Float64Array => Some(array("f64", pos)),
 
-            IdlType::Interface(name) => {
+            IdlType::Interface(name) |
+            IdlType::Dictionary(name) => {
                 let ty = ident_ty(rust_ident(camel_case_ident(name).as_str()));
                 if pos == TypePosition::Argument {
                     Some(shared_ref(ty))
@@ -475,7 +476,6 @@ impl<'a> IdlType<'a> {
                     Some(ty)
                 }
             },
-            IdlType::Dictionary(name) => Some(ident_ty(rust_ident(camel_case_ident(name).as_str()))),
             IdlType::Enum(name) => Some(ident_ty(rust_ident(camel_case_ident(name).as_str()))),
 
             IdlType::Nullable(idl_type) => Some(option_ty(idl_type.to_syn_type(pos)?)),

crates/webidl/src/lib.rs

@@ -35,14 +35,17 @@ use std::io::{self, Read};
 use std::iter::FromIterator;
 use std::path::Path;
 
+use backend::ast;
 use backend::TryToTokens;
 use backend::defined::{ImportedTypeDefinitions, RemoveUndefinedImports};
+use backend::defined::ImportedTypeReferences;
 use backend::util::{ident_ty, rust_ident, raw_ident, wrap_import_function};
 use failure::ResultExt;
 use heck::{ShoutySnakeCase, SnakeCase};
 use proc_macro2::{Ident, Span};
 use weedle::argument::Argument;
 use weedle::attribute::{ExtendedAttribute, ExtendedAttributeList};
+use weedle::dictionary::DictionaryMember;
 
 use first_pass::{FirstPass, FirstPassRecord, OperationId};
 use util::{public, webidl_const_v_to_backend_const_v, TypePosition, camel_case_ident, mdn_doc};
@@ -113,7 +116,11 @@ pub fn compile(webidl_source: &str) -> Result<String> {
 
 /// Run codegen on the AST to generate rust code.
 fn compile_ast(mut ast: backend::ast::Program) -> String {
-    let mut defined = BTreeSet::from_iter(
+    // Iteratively prune all entries from the AST which reference undefined
+    // fields. Each pass may remove definitions of types and so we need to
+    // reexecute this pass to see if we need to keep removing types until we
+    // reach a steady state.
+    let builtin = BTreeSet::from_iter(
         vec![
             "str", "char", "bool", "JsValue", "u8", "i8", "u16", "i16", "u32", "i32", "u64", "i64",
             "usize", "isize", "f32", "f64", "Result", "String", "Vec", "Option",
@@ -121,10 +128,15 @@ fn compile_ast(mut ast: backend::ast::Program) -> String {
         ].into_iter()
             .map(|id| proc_macro2::Ident::new(id, proc_macro2::Span::call_site())),
     );
+    loop {
+        let mut defined = builtin.clone();
         ast.imported_type_definitions(&mut |id| {
             defined.insert(id.clone());
         });
-    ast.remove_undefined_imports(&|id| defined.contains(id));
+        if !ast.remove_undefined_imports(&|id| defined.contains(id)) {
+            break
+        }
+    }
 
     let mut tokens = proc_macro2::TokenStream::new();
     if let Err(e) = ast.try_to_tokens(&mut tokens) {
@@ -179,6 +191,7 @@ impl<'src> WebidlParse<'src, ()> for weedle::Definition<'src> {
             | weedle::Definition::InterfaceMixin(_)
             | weedle::Definition::PartialInterfaceMixin(_)
             | weedle::Definition::IncludesStatement(..)
+            | weedle::Definition::PartialDictionary(..)
             | weedle::Definition::PartialNamespace(..)=> {
                 // handled in the first pass
             }
@@ -188,6 +201,9 @@ impl<'src> WebidlParse<'src, ()> for weedle::Definition<'src> {
             weedle::Definition::Namespace(namespace) => {
                 namespace.webidl_parse(program, first_pass, ())?
             }
+            weedle::Definition::Dictionary(dict) => {
+                dict.webidl_parse(program, first_pass, ())?
+            }
 
             // TODO
             weedle::Definition::Callback(..) => {
@@ -196,12 +212,6 @@ impl<'src> WebidlParse<'src, ()> for weedle::Definition<'src> {
             weedle::Definition::CallbackInterface(..) => {
                 warn!("Unsupported WebIDL CallbackInterface definition: {:?}", self)
             }
-            weedle::Definition::Dictionary(..) => {
-                warn!("Unsupported WebIDL Dictionary definition: {:?}", self)
-            }
-            weedle::Definition::PartialDictionary(..) => {
-                warn!("Unsupported WebIDL PartialDictionary definition: {:?}", self)
-            }
         }
         Ok(())
     }
@@ -355,8 +365,8 @@ impl<'src> WebidlParse<'src, &'src weedle::InterfaceDefinition<'src>> for Extend
                 overloaded,
                 same_argument_names,
                 &match first_pass.convert_arguments(arguments) {
+                    Some(arguments) => arguments,
                     None => return,
-                    Some(arguments) => arguments
                 },
                 IdlType::Interface(interface.identifier.0),
                 kind,
@@ -950,3 +960,114 @@ impl<'src> WebidlParse<'src, (&'src str, &'src mut backend::ast::Module)> for we
         Ok(())
     }
 }
+
+// tons more data for what's going on here at
+// https://www.w3.org/TR/WebIDL-1/#idl-dictionaries
+impl<'src> WebidlParse<'src, ()> for weedle::DictionaryDefinition<'src> {
+    fn webidl_parse(
+        &'src self,
+        program: &mut backend::ast::Program,
+        first_pass: &FirstPassRecord<'src>,
+        (): (),
+    ) -> Result<()> {
+        if util::is_chrome_only(&self.attributes) {
+            return Ok(());
+        }
+
+        let mut fields = Vec::new();
+        if !push_members(first_pass, self.identifier.0, &mut fields) {
+            return Ok(())
+        }
+
+        program.dictionaries.push(ast::Dictionary {
+            name: rust_ident(&camel_case_ident(self.identifier.0)),
+            fields,
+        });
+
+        return Ok(());
+
+        fn push_members<'src>(
+            data: &FirstPassRecord<'src>,
+            dict: &'src str,
+            dst: &mut Vec<ast::DictionaryField>,
+        ) -> bool {
+            let dict_data = &data.dictionaries[&dict];
+            let definition = dict_data.definition.unwrap();
+
+            // > The order of the dictionary members on a given dictionary is
+            // > such that inherited dictionary members are ordered before
+            // > non-inherited members ...
+            if let Some(parent) = &definition.inheritance {
+                if !push_members(data, parent.identifier.0, dst) {
+                    return false
+                }
+            }
+
+            // > ... and the dictionary members on the one dictionary
+            // > definition (including any partial dictionary definitions) are
+            // > ordered lexicographically by the Unicode codepoints that
+            // > comprise their identifiers.
+            let start = dst.len();
+            let members = definition.members.body.iter();
+            let partials = dict_data.partials.iter().flat_map(|d| &d.members.body);
+            for member in members.chain(partials) {
+                match mkfield(data, member) {
+                    Some(f) => dst.push(f),
+                    None => {
+                        warn!(
+                            "unsupported dictionary field {:?}",
+                            (dict, member.identifier.0),
+                        );
+                        // If this is required then we can't support the
+                        // dictionary at all, but if it's not required we can
+                        // avoid generating bindings for the field and keep
+                        // going otherwise.
+                        if member.required.is_some() {
+                            return false
+                        }
+                    }
+                }
+            }
+            // Note that this sort isn't *quite* right in that it is sorting
+            // based on snake case instead of the original casing which could
+            // produce inconsistent results, but should work well enough for
+            // now!
+            dst[start..].sort_by_key(|f| f.name.clone());
+
+            return true
+        }
+
+        fn mkfield<'src>(
+            data: &FirstPassRecord<'src>,
+            field: &'src DictionaryMember<'src>,
+        ) -> Option<ast::DictionaryField> {
+            // use argument position now as we're just binding setters
+            let ty = field.type_.to_idl_type(data)?.to_syn_type(TypePosition::Argument)?;
+
+            // Slice types aren't supported because they don't implement
+            // `Into<JsValue>`
+            if let syn::Type::Reference(ty) = &ty {
+                match &*ty.elem {
+                    syn::Type::Slice(_) => return None,
+                    _ => {}
+                }
+            }
+
+            // Similarly i64/u64 aren't supported because they don't
+            // implement `Into<JsValue>`
+            let mut any_64bit = false;
+            ty.imported_type_references(&mut |i| {
+                any_64bit = any_64bit || i == "u64" || i == "i64";
+            });
+            if any_64bit {
+                return None
+            }
+
+            Some(ast::DictionaryField {
+                required: field.required.is_some(),
+                name: rust_ident(&field.identifier.0.to_snake_case()),
+                ty,
+            })
+        }
+    }
+}

src/lib.rs

@@ -350,6 +350,21 @@ impl From<bool> for JsValue {
     }
 }
 
+impl<'a, T> From<&'a T> for JsValue where T: JsCast {
+    fn from(s: &'a T) -> JsValue {
+        s.as_ref().clone()
+    }
+}
+
+impl<T> From<Option<T>> for JsValue where JsValue: From<T> {
+    fn from(s: Option<T>) -> JsValue {
+        match s {
+            Some(s) => s.into(),
+            None => JsValue::undefined(),
+        }
+    }
+}
+
 impl JsCast for JsValue {
     // everything is a `JsValue`!
     fn instanceof(_val: &JsValue) -> bool { true }