refactor/simplify nullable inference code

lib/src/utils.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.
 
 /// Holds a couple utility functions used at various places in the system.
 
 import 'dart:io';
-
 import 'package:path/path.dart' as path;
 import 'package:analyzer/src/generated/ast.dart'
     show
         ImportDirective,
         ExportDirective,
         PartDirective,
         CompilationUnit,
         Identifier,
         AnnotatedNode,
         AstNode,
@@ skipping 428 matching lines @@
 
 /// Gets the "simple" name of an enum value.
 getEnumName(v) {
   var parts = '$v'.split('.');
   if (parts.length != 2 || !parts.every((p) => p.isNotEmpty)) {
     throw new ArgumentError('Invalid enum value: $v');
   }
   return parts[1];
 }
 
-/// Simplistic directed graph.
-class DirectedGraph<V> {
-  final _adjacencyList = <V, Set<V>>{};
-
-  void addEdge(V from, V to) {
-    _adjacencyList.putIfAbsent(from, () => new Set<V>()).add(to);
-  }
-
-  /// Get all the vertices reachable from the provided [roots].
-  Set<V> getTransitiveClosure(Iterable<V> roots) {
-    final reached = new Set<V>();
-
-    visit(V e) {
-      if (reached.add(e)) {
-        var destinations = _adjacencyList[e];
-        if (destinations != null) destinations.forEach(visit);
-      }
-    }
-    roots.forEach(visit);
-
-    return reached;
-  }
-}
-
 class FileSystem {
   const FileSystem();
 
   void _ensureParentExists(String file) {
     var dir = new Directory(path.dirname(file));
     if (!dir.existsSync()) dir.createSync(recursive: true);
   }
 
   void copySync(String source, String destination) {
     _ensureParentExists(destination);
     new File(source).copySync(destination);
   }
 
   void writeAsStringSync(String file, String contents) {
     _ensureParentExists(file);
     new File(file).writeAsStringSync(contents);
   }
 }
+
+DartType getStaticType(Expression e) =>
+    e.staticType ?? DynamicTypeImpl.instance;