Add support for building patched_sdk and platform.dill for dart2js:

pkg/compiler/lib/src/kernel/fasta_support.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Additions to Fasta for generating .dill (Kernel IR) files with dart2js patch
+/// files and native hooks.
+library compiler.src.kernel.fasta_support;
+
+// TODO(sigmund): get rid of this file. Fasta should be agnostic of the
+// target platform, at which point this should not be necessary. In particular,
+// we need to:
+//  - add a fasta flag to configure the platform library location.
+//  - add a fasta flag to specify which sdk libraries should be built-in
+//    (that would replace `loadExtraRequiredLibraries`).
+//  - add flags to fasta to turn on various transformations.
+//  - get rid of `native` in dart2js patches or unify the syntax with the VM.
+
+import 'dart:async' show Future;
+import 'dart:io' show exitCode;
+
+import 'package:kernel/ast.dart' show Source;
+
+import 'package:front_end/src/fasta/compiler_context.dart' show CompilerContext;
+import 'package:front_end/src/fasta/dill/dill_target.dart' show DillTarget;
+import 'package:front_end/src/fasta/fasta.dart' show CompileTask;
+import 'package:front_end/src/fasta/kernel/kernel_target.dart'
+    show KernelTarget;
+import 'package:front_end/src/fasta/loader.dart' show Loader;
+import 'package:front_end/src/fasta/parser/parser.dart' show optional;
+import 'package:front_end/src/fasta/scanner/token.dart' show Token;
+import 'package:front_end/src/fasta/ticker.dart' show Ticker;
+import 'package:front_end/src/fasta/translate_uri.dart' show TranslateUri;
+
+/// Generates a platform.dill file containing the compiled Kernel IR of the
+/// dart2js SDK.
+Future compilePlatform(Uri patchedSdk, Uri output, {Uri packages}) async {
+  Uri deps = Uri.base.resolveUri(new Uri.file("${output.toFilePath()}.d"));
+  TranslateUri uriTranslator = await TranslateUri.parse(patchedSdk, packages);
+  var ticker = new Ticker(isVerbose: false);
+  var dillTarget = new DillTargetForDart2js(ticker, uriTranslator);
+  var kernelTarget =
+      new KernelTargetForDart2js(dillTarget, uriTranslator, false);
+
+  kernelTarget.read(Uri.parse("dart:core"));
+  await dillTarget.writeOutline(null);
+  await kernelTarget.writeOutline(output);
+
+  if (exitCode != 0) return null;
+  await kernelTarget.writeProgram(output);
+  await kernelTarget.writeDepsFile(output, deps);
+}
+
+/// Extends the internal fasta [CompileTask] to use a dart2js-aware [DillTarget]
+/// and [KernelTarget].
+class Dart2jsCompileTask extends CompileTask {
+  Dart2jsCompileTask(CompilerContext c, Ticker ticker) : super(c, ticker);
+
+  @override
+  DillTarget createDillTarget(TranslateUri uriTranslator) {
+    return new DillTargetForDart2js(ticker, uriTranslator);
+  }
+
+  @override
+  KernelTarget createKernelTarget(
+      DillTarget dillTarget, TranslateUri uriTranslator, bool strongMode) {
+    return new KernelTargetForDart2js(
+        dillTarget, uriTranslator, strongMode, c.uriToSource);
+  }
+}
+
+/// Specializes [KernelTarget] to build kernel for dart2js: no transformations
+/// are run, JS-specific libraries are included in the SDK, and native clauses
+/// have no string parameter.
+class KernelTargetForDart2js extends KernelTarget {
+  KernelTargetForDart2js(
+      DillTarget target, TranslateUri uriTranslator, bool strongMode,
+      [Map<String, Source> uriToSource])
+      : super(target, uriTranslator, strongMode, uriToSource);
+
+  @override
+  Token skipNativeClause(Token token) => _skipNative(token);
+
+  @override
+  String extractNativeMethodName(Token token) => null;
+
+  @override
+  void loadExtraRequiredLibraries(Loader loader) => _loadExtras(loader);
+
+  @override
+  void runBuildTransformations() {}
+
+  @override
+  void runLinkTransformations(_) {}
+}
+
+/// Specializes [DillTarget] to build kernel for dart2js: JS-specific libraries
+/// are included in the SDK, and native clauses have no string parameter.
+class DillTargetForDart2js extends DillTarget {
+  DillTargetForDart2js(Ticker ticker, TranslateUri uriTranslator)
+      : super(ticker, uriTranslator);
+
+  @override
+  Token skipNativeClause(Token token) => _skipNative(token);
+
+  @override
+  String extractNativeMethodName(Token token) => null;
+
+  @override
+  void loadExtraRequiredLibraries(Loader loader) => _loadExtras(loader);
+}
+
+/// We use native clauses of this form in our dart2js patch files:
+///
+///     methodDeclaration() native;
+///
+/// The default front_end parser doesn't support this, so it will trigger an
+/// error recovery condition. This function is used while parsing to detect this
+/// form and continue parsing.
+///
+/// Note that `native` isn't part of the Dart Language Specification, and the VM
+/// uses it a slightly different form. We hope to remove this syntax in our
+/// dart2js patch files and replace it with the external modifier.
+Token _skipNative(Token token) {
+  if (!optional("native", token)) return null;
+  if (!optional(";", token.next)) return null;
+  return token;
+}
+
+void _loadExtras(Loader loader) {
+  for (String uri in _extraDart2jsLibraries) {
+    loader.read(Uri.parse(uri));
+  }
+}
+
+const _extraDart2jsLibraries = const <String>[
+  'dart:async',
+  'dart:collection',
+  'dart:mirrors',
+  'dart:_native_typed_data',
+  'dart:_internal',
+  'dart:_js_helper',
+  'dart:_interceptors',
+  'dart:_foreign_helper',
+  'dart:_js_mirrors',
+  'dart:_js_names',
+  'dart:_js_embedded_names',
+  'dart:_isolate_helper',
+];