Introduce the wasm-bindgen-webidl frontend

This is still a work in progress. Parse WebIDL source text and convert it into
wasm-bindgen AST, so that we can automatically emit bindings for the types and
functions described in the WebIDL.

crates/webidl/tests/all/Event.webidl

@@ -0,0 +1,59 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * The origin of this IDL file is
+ * http://www.w3.org/TR/2012/WD-dom-20120105/
+ *
+ * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
+ * liability, trademark and document use rules apply.
+ */
+
+[Constructor(DOMString type, optional EventInit eventInitDict),
+ Exposed=(Window,Worker,System), ProbablyShortLivingWrapper]
+interface Event {
+  [Pure]
+  readonly attribute DOMString type;
+  [Pure]
+  readonly attribute EventTarget? target;
+  [Pure]
+  readonly attribute EventTarget? currentTarget;
+
+  sequence<EventTarget> composedPath();
+
+  const unsigned short NONE = 0;
+  const unsigned short CAPTURING_PHASE = 1;
+  const unsigned short AT_TARGET = 2;
+  const unsigned short BUBBLING_PHASE = 3;
+  [Pure]
+  readonly attribute unsigned short eventPhase;
+
+  void stopPropagation();
+  void stopImmediatePropagation();
+
+  [Pure]
+  readonly attribute boolean bubbles;
+  [Pure]
+  readonly attribute boolean cancelable;
+  [NeedsCallerType]
+  void preventDefault();
+  [Pure, NeedsCallerType]
+  readonly attribute boolean defaultPrevented;
+  [ChromeOnly, Pure]
+  readonly attribute boolean defaultPreventedByChrome;
+  [ChromeOnly, Pure]
+  readonly attribute boolean defaultPreventedByContent;
+  [Pure]
+  readonly attribute boolean composed;
+
+  [Unforgeable, Pure]
+  readonly attribute boolean isTrusted;
+  [Pure]
+  readonly attribute DOMHighResTimeStamp timeStamp;
+
+  void initEvent(DOMString type,
+                 optional boolean bubbles = false,
+                 optional boolean cancelable = false);
+  attribute boolean cancelBubble;
+};

crates/webidl/tests/all/event.rs

@@ -0,0 +1,24 @@
+use super::backend;
+use proc_macro2;
+use syn;
+
+assert_parse!(
+    event,
+    include_str!("./Event.webidl"),
+    backend::ast::Program {
+        exports: vec![],
+        imports: vec![backend::ast::Import {
+            module: None,
+            version: None,
+            js_namespace: None,
+            kind: backend::ast::ImportKind::Type(backend::ast::ImportType {
+                vis: syn::Visibility::Public(syn::VisPublic {
+                    pub_token: syn::token::Pub(proc_macro2::Span::call_site()),
+                }),
+                name: syn::Ident::new("Event", proc_macro2::Span::call_site()),
+            }),
+        }],
+        enums: vec![],
+        structs: vec![],
+    }
+);

crates/webidl/tests/all/lib.rs

@@ -0,0 +1,21 @@
+extern crate proc_macro2;
+extern crate syn;
+extern crate wasm_bindgen_backend as backend;
+extern crate wasm_bindgen_webidl as wb_webidl;
+
+pub fn assert_parse(webidl: &str, expected: backend::ast::Program) {
+    let actual = wb_webidl::parse(webidl).expect("should parse the webidl source OK");
+    assert_eq!(expected, actual);
+}
+
+macro_rules! assert_parse {
+    ($test_name:ident, $webidl_source:expr, $expected_ast:expr) => {
+        #[test]
+        fn $test_name() {
+            $crate::assert_parse($webidl_source, $expected_ast);
+        }
+    };
+}
+
+mod event;
+mod simple;

crates/webidl/tests/all/simple.rs

@@ -0,0 +1,3 @@
+use super::backend;
+
+assert_parse!(empty, "", backend::ast::Program::default());