Add more debugging code

pkg/analyzer/lib/src/task/dart.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.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 2934 matching lines @@
       InternalAnalysisContext context, VariableElement variable)
       : super(context, variable);
 
   /**
    * Return the declaration of the target within the given compilation [unit].
    * Throw an exception if the declaration cannot be found.
    */
   VariableDeclaration getDeclaration(CompilationUnit unit) {
     VariableElement variable = target;
     AstNode node = new NodeLocator2(variable.nameOffset).searchWithin(unit);
+    if (node == null) {
+      Source variableSource = variable.source;
+      Source unitSource = unit.element.source;
+      if (variableSource != unitSource) {
+        throw new AnalysisException(
+            "Failed to find the AST node for the variable "
+            "${variable.displayName} in $variableSource "
+            "because we were looking in $unitSource");
+      }
+      throw new AnalysisException(
+          "Failed to find the AST node for the variable "
+          "${variable.displayName} in $variableSource");
+    }
     VariableDeclaration declaration =
         node.getAncestor((AstNode ancestor) => ancestor is VariableDeclaration);
     if (declaration == null || declaration.name != node) {
+      Source variableSource = variable.source;
+      Source unitSource = unit.element.source;
+      if (variableSource != unitSource) {
+        throw new AnalysisException(
+            "Failed to find the declaration of the variable "
+            "${variable.displayName} in $variableSource"
+            "because we were looking in $unitSource");
+      }
       throw new AnalysisException(
           "Failed to find the declaration of the variable "
-          "${variable.displayName} in ${variable.source}");
+          "${variable.displayName} in $variableSource");
     }
     return declaration;
   }
 }
 
 /**
  * A task that ensures that all of the inferable static variables in a
  * compilation unit have had their type inferred.
  */
 class InferStaticVariableTypesInUnitTask extends SourceBasedAnalysisTask {
@@ skipping 933 matching lines @@
     outputs[PROPAGATED_VARIABLE] = variable;
   }
 
   /**
    * Return a map from the names of the inputs of this kind of task to the task
    * input descriptors describing those inputs for a task with the given
    * [target].
    */
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     VariableElement variable = target;
+    if (variable.library == null) {
+      StringBuffer buffer = new StringBuffer();
+      buffer.write(
+          'PropagateVariableTypeTask building inputs for a variable with no library. Variable name = "');
+      buffer.write(variable.name);
+      buffer.write('". Path = ');
+      (variable as ElementImpl).appendPathTo(buffer);
+      throw new AnalysisException(buffer.toString());
+    }
     LibrarySpecificUnit unit =
         new LibrarySpecificUnit(variable.library.source, variable.source);
     return <String, TaskInput>{
       'dependencies': PROPAGABLE_VARIABLE_DEPENDENCIES
           .of(variable)
           .toListOf(PROPAGATED_VARIABLE),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
       UNIT_INPUT: RESOLVED_UNIT5.of(unit),
     };
   }
@@ skipping 1188 matching lines @@
     RecordingErrorListener errorListener = new RecordingErrorListener();
     Source source = getRequiredSource();
     errorReporter = new ErrorReporter(errorListener, source);
     //
     // Prepare inputs.
     //
     TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
     CompilationUnit unit = getRequiredInput(UNIT_INPUT);
     CompilationUnitElement unitElement = unit.element;
     LibraryElement libraryElement = unitElement.library;
+    if (libraryElement == null) {
+      throw new AnalysisException(
+          'VerifyUnitTask verifying constants in a unit with no library: '

[scheglov, 2016/03/11 18:57:12]

Hm... Why do you mention constants here?
Isn't it a problem in general if we get a unit element outside of a library?

[Brian Wilkerson, 2016/03/11 19:04:54]

Incomplete clean up after copy paste. Thanks for catching it.

+          '${unitElement.source.fullName}');
+    }
     //
     // Validate the directives.
     //
     validateDirectives(unit);
     //
     // Use the ConstantVerifier to compute errors.
     //
     ConstantVerifier constantVerifier = new ConstantVerifier(
         errorReporter, libraryElement, typeProvider, context.declaredVariables);
     unit.accept(constantVerifier);
@@ skipping 170 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }