Implement line and column numbers.

pkg/front_end/lib/src/fasta/compiler_context.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.
+
+library fasta.compiler_context;
+
+import 'dart:async' show
+    Zone,
+    runZoned;
+
+import 'package:kernel/ast.dart' show
+    Source;
+
+import 'compiler_command_line.dart' show
+    CompilerCommandLine;
+
+final Object compilerContextKey = new Object();
+
+final CompilerContext rootContext =
+    new CompilerContext(CompilerCommandLine.forRootContext());
+
+class CompilerContext {
+  final CompilerCommandLine options;
+
+  final Map<String, Source> uriToSource = <String, Source>{};
+
+  CompilerContext(this.options);
+
+  static CompilerContext get current {
+    return Zone.current[compilerContextKey] ?? rootContext;
+  }
+
+  /// Perform [action] in a [Zone] where [cl] will be available as
+  /// `CompilerContext.current.options`.
+  static dynamic withGlobalOptions(CompilerCommandLine cl,
+      dynamic action(CompilerContext c)) {
+    CompilerContext c = new CompilerContext(cl);
+    return runZoned(() => action(c), zoneValues: {compilerContextKey: c});
+  }
+}