Add widget to display errors, and report dependency_graph errors correctly

lib/src/info.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.
 
 /// Defines static information collected by the type checker and used later by
 /// emitters to generate code.
 library dev_compiler.src.info;
 
 import 'dart:mirrors';
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/scanner.dart'
     show Token, TokenType, SyntheticStringToken;
 import 'package:logging/logging.dart' show Level;
 
 import 'package:dev_compiler/src/checker/rules.dart';
 import 'package:dev_compiler/src/utils.dart' as utils;
 
+import 'report.dart' show Message;
+
 /// Represents a summary of the results collected by running the program
 /// checker.
 class CheckerResults {
   final List<LibraryInfo> libraries;
   final TypeRules rules;
   final bool failure;
 
   CheckerResults(this.libraries, this.rules, this.failure);
 }
 
@@ skipping 77 matching lines @@
       : super(fromType, toType);
 }
 
 // The error coercion.  This coercion signals that a coercion
 // could not be generated.  The code generator should not see
 // these.
 class CoercionError extends Coercion {
   CoercionError() : super(null, null);
 }
 
-abstract class StaticInfo {
+abstract class StaticInfo implements Message {
   /// AST Node this info is attached to.
   // TODO(jmesserly): this is somewhat redundant with SemanticNode.
   AstNode get node;
 
-  /// Log level for error messages.  This is a placeholder
-  /// for severity.
-  Level get level;
+  @override
+  int get begin => node is AnnotatedNode
+      ? (node as AnnotatedNode).firstTokenAfterCommentAndMetadata.offset
+      : node.offset;
 
-  /// Description / error message.
-  String get message;
+  @override
+  int get end => node.end;
 }
 
 /// Implicitly injected expression conversion.
 // TODO(jmesserly): rename to have Expression suffix?
-abstract class Conversion extends Expression implements StaticInfo {
+abstract class Conversion extends Expression with StaticInfo {
   final TypeRules rules;
 
   // TODO(jmesserly): should probably rename this "operand" for consistency with
   // analyzer's unary expressions (e.g. PrefixExpression).
   final Expression expression;
 
   AstNode get node => expression;
   DartType _convertedType;
 
   Conversion(this.rules, this.expression) {
@@ skipping 436 matching lines @@
   for (var cls in declarations.where((d) => d is ClassMirror)) {
     if (cls.isSubtypeOf(infoMirror)) {
       allTypes.add(cls);
       baseTypes.add(cls.superclass);
     }
   }
   allTypes.removeAll(baseTypes);
   return new List<Type>.from(allTypes.map((mirror) => mirror.reflectedType))
     ..sort((t1, t2) => '$t1'.compareTo('$t2'));
 }();