Record variable names in type inference cycles.

pkg/analyzer/lib/src/summary/link.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.
 
 /**
  * This library is capable of producing linked summaries from unlinked
  * ones (or prelinked ones).  It functions by building a miniature
  * element model to represent the contents of the summaries, and then
  * scanning the element model to gather linked information and adding
  * it to the summary data structures.
@@ skipping 4779 matching lines @@
 }
 
 /**
  * Specialization of [DependencyWalker] for performing type inferrence
  * on static and top level variables.
  */
 class TypeInferenceDependencyWalker
     extends DependencyWalker<TypeInferenceNode> {
   @override
   void evaluate(TypeInferenceNode v) {
-    v.evaluate(false);
+    v.evaluate(null);
   }
 
   @override
   void evaluateScc(List<TypeInferenceNode> scc) {
     for (TypeInferenceNode v in scc) {
-      v.evaluate(true);
+      v.evaluate(scc);
     }
   }
 }
 
 /**
  * Specialization of [Node] used to construct the type inference dependency
  * graph.
  */
 class TypeInferenceNode extends Node<TypeInferenceNode> {
   /**
@@ skipping 98 matching lines @@
   }
 
   @override
   List<TypeInferenceNode> computeDependencies() {
     List<TypeInferenceNode> dependencies = <TypeInferenceNode>[];
     collectDependencies(dependencies, functionElement._unlinkedExecutable,
         functionElement.compilationUnit);
     return dependencies;
   }
 
-  void evaluate(bool inCycle) {
-    if (inCycle) {
+  void evaluate(List<TypeInferenceNode> cycle) {
+    if (cycle != null) {
+      List<String> cycleNames = cycle
+          .map((node) {
+            Element e = node.functionElement;
+            while (e != null) {
+              if (e is VariableElement) {
+                return e.name;
+              }
+              e = e.enclosingElement;
+            }
+            return '<unknown>';
+          })
+          .toSet()
+          .toList();
       functionElement._setInferenceError(new TopLevelInferenceErrorBuilder(
-          kind: TopLevelInferenceErrorKind.dependencyCycle));
+          kind: TopLevelInferenceErrorKind.dependencyCycle,
+          arguments: cycleNames));
       functionElement._setInferredType(DynamicTypeImpl.instance);
     } else {
       var computer = new ExprTypeComputer(functionElement);
       DartType bodyType = computer.compute();
       if (computer.errorKind != null) {
         functionElement._setInferenceError(
             new TopLevelInferenceErrorBuilder(kind: computer.errorKind));
         functionElement._setInferredType(DynamicTypeImpl.instance);
       } else {
         if (functionElement.isAsynchronous) {
@@ skipping 341 matching lines @@
 }
 
 /**
  * This exception is thrown when [ExprTypeComputer] cannot inference the type.
  */
 class _InferenceFailedError {
   final String message;
 
   _InferenceFailedError(this.message);
 }