Merge the work on Generic Types Reification from 'dart-lang/reify' repo

pkg/kernel/lib/transformations/reify/asts.dart

+// Copyright (c) 2016, 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 kernel.transformations.reify.ast_helpers;
+
+import 'package:kernel/ast.dart';
+
+Class getEnclosingClass(TreeNode node) {
+  TreeNode original = node;
+  while (node != null && node is! Class) {
+    node = node.parent;
+  }
+  if (node == null) {
+    throw 'internal error: enclosing class not found for $original';
+  }
+  return node;
+}
+
+Library getEnclosingLibrary(TreeNode node) {
+  TreeNode original = node;
+  while (node != null && node is! Library) {
+    node = node.parent;
+  }
+  if (node == null) {
+    throw 'internal error: enclosing library not found for $original';
+  }
+  return node;
+}
+
+Member getEnclosingMember(TreeNode node) {
+  TreeNode original = node;
+  while (node != null && node is! Member) {
+    node = node.parent;
+  }
+  if (node == null) {
+    throw 'internal error: enclosing member not found for $original';
+  }
+  return node;
+}
+
+List<TypeParameter> typeVariables(DartType type) {
+  List<TypeParameter> parameters = <TypeParameter>[];
+  collect(DartType type) {
+    if (type is InterfaceType) {
+      type.typeArguments.map(collect);
+    } else if (type is TypeParameterType) {
+      parameters.add(type.parameter);
+    }
+  }
+
+  collect(type);
+  return parameters;
+}