Initial steps toward adding strong mode to the new task model

pkg/analyzer/lib/src/task/strong_mode.dart

+// Copyright (c) 2015, 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 analyzer.src.task.strong_mode;
+
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
+
+/**
+ * An object used to find static variables whose types should be inferred and
+ * classes whose members should have types inferred. Clients are expected to
+ * visit a [CompilationUnit].
+ */
+class InferrenceFinder extends SimpleAstVisitor {
+  /**
+   * The static variables that should have types inferred for them.
+   */
+  final List<VariableElement> staticVariables = <VariableElement>[];
+
+  /**
+   * The classes defined in the unit.
+   *
+   * TODO(brianwilkerson) We don't currently remove classes whose members do not
+   * need to be processed, but we potentially could.
+   */
+  final List<ClassElement> classes = <ClassElement>[];
+
+  /**
+   * Initialize a newly created finder.
+   */
+  InferrenceFinder();
+
+  @override
+  void visitClassDeclaration(ClassDeclaration node) {
+    classes.add(node.element);
+    for (ClassMember member in node.members) {
+      member.accept(this);
+    }
+  }
+
+  @override
+  void visitClassTypeAlias(ClassTypeAlias node) {
+    classes.add(node.element);
+  }
+
+  @override
+  void visitCompilationUnit(CompilationUnit node) {
+    for (CompilationUnitMember declaration in node.declarations) {
+      declaration.accept(this);
+    }
+  }
+
+  @override
+  void visitFieldDeclaration(FieldDeclaration node) {
+    if (node.isStatic && node.fields.type == null) {
+      _addVariables(node.fields.variables);
+    }
+  }
+
+  @override
+  void visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
+    if (node.variables.type == null) {
+      _addVariables(node.variables.variables);
+    }
+  }
+
+  /**
+   * Add all of the [variables] with initializers to the list of variables whose
+   * type can be inferred. Technically, we only infer the types of variables
+   * that do not have a static type, but all variables with initializers
+   * potentially need to be re-resolved after inference because they might
+   * refer to fields whose type was inferred.
+   */
+  void _addVariables(NodeList<VariableDeclaration> variables) {
+    for (VariableDeclaration variable in variables) {
+      if (variable.initializer != null) {
+        staticVariables.add(variable.element);
+      }
+    }
+  }
+}