Propagate types of final/const top-level variables and fields.

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

Index: pkg/analyzer/lib/src/task/dart.dart
diff --git a/pkg/analyzer/lib/src/task/dart.dart b/pkg/analyzer/lib/src/task/dart.dart
index 2aae1a1f3dcb828444726b8985bd423ea4a1dbc9..4465b2467c17e083f7340c253c8f64297d53f6cb 100644
--- a/pkg/analyzer/lib/src/task/dart.dart
+++ b/pkg/analyzer/lib/src/task/dart.dart
@@ -338,6 +338,36 @@ final ListResultDescriptor<AnalysisError> PARSE_ERRORS =
         'PARSE_ERRORS', AnalysisError.NO_ERRORS);
 
 /**
+ * A list of the [VariableElement]s whose type should be known to propagate
+ * the type of another variable (the target).
+ *
+ * The result is only available for [VariableElement]s.
+ */
+final ListResultDescriptor<VariableElement> PROPAGABLE_VARIABLE_DEPENDENCIES =
+    new ListResultDescriptor<VariableElement>(
+        'PROPAGABLE_VARIABLE_DEPENDENCIES', null);
+
+/**
+ * A list of the [VariableElement]s defined in a unit whose type might be
+ * propagated. This includes variables defined at the library level as well as
+ * static and instance members inside classes.
+ *
+ * The result is only available for [LibrarySpecificUnit]s.
+ */
+final ListResultDescriptor<VariableElement> PROPAGABLE_VARIABLES_IN_UNIT =
+    new ListResultDescriptor<VariableElement>(
+        'PROPAGABLE_VARIABLES_IN_UNIT', null);
+
+/**
+ * An propagable variable ([VariableElement]) whose type has been propagated.
+ *
+ * The result is only available for [VariableElement]s.
+ */
+final ResultDescriptor<VariableElement> PROPAGATED_VARIABLE =
+    new ResultDescriptor<VariableElement>('PROPAGATED_VARIABLE', null,
+        cachingPolicy: ELEMENT_CACHING_POLICY);
+
+/**
  * The flag specifying that [LIBRARY_ELEMENT2] is ready for a library and its
  * import/export closure.
  *
@@ -365,7 +395,7 @@ final ResultDescriptor<bool> READY_RESOLVED_UNIT =
     new ResultDescriptor<bool>('READY_RESOLVED_UNIT', false);
 
 /**
- * The flag specifying that [RESOLVED_UNIT10] is ready for all of the units of a
+ * The flag specifying that [RESOLVED_UNIT11] is ready for all of the units of a
  * library and its import/export closure.
  *
  * The result is only available for [Source]s representing a library.
@@ -374,7 +404,7 @@ final ResultDescriptor<bool> READY_RESOLVED_UNIT10 =
     new ResultDescriptor<bool>('READY_RESOLVED_UNIT10', false);
 
 /**
- * The flag specifying that [RESOLVED_UNIT9] is ready for all of the units of a
+ * The flag specifying that [RESOLVED_UNIT10] is ready for all of the units of a
  * library and its import/export closure.
  *
  * The result is only available for [Source]s representing a library.
@@ -427,7 +457,7 @@ final ResultDescriptor<CompilationUnit> RESOLVED_UNIT1 =
 
 /**
  * The resolved [CompilationUnit] associated with a compilation unit, with
- * constants resolved.
+ * constants not yet resolved.
  *
  * The result is only available for [LibrarySpecificUnit]s.
  */
@@ -436,6 +466,16 @@ final ResultDescriptor<CompilationUnit> RESOLVED_UNIT10 =
         cachingPolicy: AST_CACHING_POLICY);
 
 /**
+ * The resolved [CompilationUnit] associated with a compilation unit, with
+ * constants resolved.
+ *
+ * The result is only available for [LibrarySpecificUnit]s.
+ */
+final ResultDescriptor<CompilationUnit> RESOLVED_UNIT11 =
+    new ResultDescriptor<CompilationUnit>('RESOLVED_UNIT11', null,
+        cachingPolicy: AST_CACHING_POLICY);
+
+/**
  * The partially resolved [CompilationUnit] associated with a compilation unit.
  *
  * Tasks that use this value as an input can assume that the [SimpleIdentifier]s
@@ -493,7 +533,8 @@ final ResultDescriptor<CompilationUnit> RESOLVED_UNIT5 =
  * The partially resolved [CompilationUnit] associated with a compilation unit.
  *
  * In addition to what is true of a [RESOLVED_UNIT5], tasks that use this value
- * as an input can assume that the types of static variables have been inferred.
+ * as an input can assume that the types of final variables have been
+ * propagated.
  *
  * The result is only available for [LibrarySpecificUnit]s.
  */
@@ -505,8 +546,7 @@ final ResultDescriptor<CompilationUnit> RESOLVED_UNIT6 =
  * The partially resolved [CompilationUnit] associated with a compilation unit.
  *
  * In addition to what is true of a [RESOLVED_UNIT6], tasks that use this value
- * as an input can assume that the initializers of instance variables have been
- * re-resolved.
+ * as an input can assume that the types of static variables have been inferred.
  *
  * The result is only available for [LibrarySpecificUnit]s.
  */
@@ -515,9 +555,11 @@ final ResultDescriptor<CompilationUnit> RESOLVED_UNIT7 =
         cachingPolicy: AST_CACHING_POLICY);
 
 /**
- * The resolved [CompilationUnit] associated with a compilation unit in which
- * the types of class members have been inferred in addition to everything that
- * is true of a [RESOLVED_UNIT7].
+ * The partially resolved [CompilationUnit] associated with a compilation unit.
+ *
+ * In addition to what is true of a [RESOLVED_UNIT7], tasks that use this value
+ * as an input can assume that the initializers of instance variables have been
+ * re-resolved.
  *
  * The result is only available for [LibrarySpecificUnit]s.
  */
@@ -526,8 +568,9 @@ final ResultDescriptor<CompilationUnit> RESOLVED_UNIT8 =
         cachingPolicy: AST_CACHING_POLICY);
 
 /**
- * The resolved [CompilationUnit] associated with a compilation unit, with
- * constants not yet resolved.
+ * The resolved [CompilationUnit] associated with a compilation unit in which
+ * the types of class members have been inferred in addition to everything that
+ * is true of a [RESOLVED_UNIT8].
  *
  * The result is only available for [LibrarySpecificUnit]s.
  */
@@ -1638,7 +1681,7 @@ class ComputeConstantDependenciesTask extends ConstantEvaluationAnalysisTask {
           'Cannot build inputs for a ${target.runtimeType}');
     }
     return <String, TaskInput>{
-      'resolvedUnit': RESOLVED_UNIT9
+      'resolvedUnit': RESOLVED_UNIT10
           .of(new LibrarySpecificUnit(librarySource, target.source)),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
     };
@@ -1940,6 +1983,92 @@ class ComputeLibraryCycleTask extends SourceBasedAnalysisTask {
 }
 
 /**
+ * A task that computes the [PROPAGABLE_VARIABLE_DEPENDENCIES] for a variable.
+ */
+class ComputePropagableVariableDependenciesTask
+    extends ConstantEvaluationAnalysisTask {
+  /**
+   * The name of the [RESOLVED_UNIT5] input.
+   */
+  static const String UNIT_INPUT = 'UNIT_INPUT';
+
+  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
+      'ComputePropagableVariableDependenciesTask',
+      createTask,
+      buildInputs,
+      <ResultDescriptor>[PROPAGABLE_VARIABLE_DEPENDENCIES]);
+
+  ComputePropagableVariableDependenciesTask(
+      InternalAnalysisContext context, VariableElement variable)
+      : super(context, variable);
+
+  @override
+  TaskDescriptor get descriptor => DESCRIPTOR;
+
+  @override
+  void internalPerform() {
+    //
+    // Prepare inputs.
+    //
+    VariableElement variable = target;
+    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
+    //
+    // Compute dependencies.
+    //
+    NodeLocator locator = new NodeLocator(variable.nameOffset);
+    AstNode node = locator.searchWithin(unit);
+    VariableDeclaration declaration =
+        node.getAncestor((AstNode ancestor) => ancestor is VariableDeclaration);
+    if (declaration == null || declaration.name != node) {
+      throw new AnalysisException(
+          "NodeLocator failed to find a variable's declaration");
+    }
+    VariableGatherer gatherer = new VariableGatherer(_isPropagable);
+    declaration.initializer.accept(gatherer);
+    //
+    // Record outputs.
+    //
+    outputs[PROPAGABLE_VARIABLE_DEPENDENCIES] = gatherer.results.toList();
+  }
+
+  /**
+   * Return `true` if the given [variable] is a variable whose type can be
+   * propagated.
+   */
+  bool _isPropagable(VariableElement variable) =>
+      (variable.isConst || variable.isFinal) &&
+          variable.hasImplicitType &&
+          variable.initializer != null;
+
+  /**
+   * 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) {
+    if (target is VariableElement) {
+      CompilationUnitElementImpl unit = target
+          .getAncestor((Element element) => element is CompilationUnitElement);
+      return <String, TaskInput>{
+        UNIT_INPUT: RESOLVED_UNIT5
+            .of(new LibrarySpecificUnit(unit.librarySource, unit.source))
+      };
+    }
+    throw new AnalysisException(
+        'Cannot build inputs for a ${target.runtimeType}');
+  }
+
+  /**
+   * Create a [ComputePropagableVariableDependenciesTask] based on the
+   * given [target] in the given [context].
+   */
+  static ComputePropagableVariableDependenciesTask createTask(
+      AnalysisContext context, AnalysisTarget target) {
+    return new ComputePropagableVariableDependenciesTask(context, target);
+  }
+}
+
+/**
  * A base class for analysis tasks whose target is expected to be a
  * [ConstantEvaluationTarget].
  */
@@ -2202,11 +2331,11 @@ class DartErrorsTask extends SourceBasedAnalysisTask {
 }
 
 /**
- * A task that builds [RESOLVED_UNIT10] for a unit.
+ * A task that builds [RESOLVED_UNIT11] for a unit.
  */
 class EvaluateUnitConstantsTask extends SourceBasedAnalysisTask {
   /**
-   * The name of the [RESOLVED_UNIT9] input.
+   * The name of the [RESOLVED_UNIT10] input.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
 
@@ -2222,7 +2351,7 @@ class EvaluateUnitConstantsTask extends SourceBasedAnalysisTask {
       'EvaluateUnitConstantsTask',
       createTask,
       buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT10]);
+      <ResultDescriptor>[RESOLVED_UNIT11]);
 
   EvaluateUnitConstantsTask(AnalysisContext context, LibrarySpecificUnit target)
       : super(context, target);
@@ -2235,7 +2364,7 @@ class EvaluateUnitConstantsTask extends SourceBasedAnalysisTask {
     // No actual work needs to be performed; the task manager will ensure that
     // all constants are evaluated before this method is called.
     CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    outputs[RESOLVED_UNIT10] = unit;
+    outputs[RESOLVED_UNIT11] = unit;
   }
 
   /**
@@ -2247,7 +2376,7 @@ class EvaluateUnitConstantsTask extends SourceBasedAnalysisTask {
     LibrarySpecificUnit unit = target;
     return <String, TaskInput>{
       'libraryElement': LIBRARY_ELEMENT.of(unit.library),
-      UNIT_INPUT: RESOLVED_UNIT9.of(unit),
+      UNIT_INPUT: RESOLVED_UNIT10.of(unit),
       CONSTANT_VALUES:
           COMPILATION_UNIT_CONSTANTS.of(unit).toListOf(CONSTANT_VALUE)
     };
@@ -2371,7 +2500,7 @@ class ExportNamespaceBuilder {
  */
 class GatherUsedImportedElementsTask extends SourceBasedAnalysisTask {
   /**
-   * The name of the [RESOLVED_UNIT9] input.
+   * The name of the [RESOLVED_UNIT10] input.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
 
@@ -2415,7 +2544,7 @@ class GatherUsedImportedElementsTask extends SourceBasedAnalysisTask {
    */
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     LibrarySpecificUnit unit = target;
-    return <String, TaskInput>{UNIT_INPUT: RESOLVED_UNIT9.of(unit)};
+    return <String, TaskInput>{UNIT_INPUT: RESOLVED_UNIT10.of(unit)};
   }
 
   /**
@@ -2433,7 +2562,7 @@ class GatherUsedImportedElementsTask extends SourceBasedAnalysisTask {
  */
 class GatherUsedLocalElementsTask extends SourceBasedAnalysisTask {
   /**
-   * The name of the [RESOLVED_UNIT9] input.
+   * The name of the [RESOLVED_UNIT10] input.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
 
@@ -2477,7 +2606,7 @@ class GatherUsedLocalElementsTask extends SourceBasedAnalysisTask {
    */
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     LibrarySpecificUnit unit = target;
-    return <String, TaskInput>{UNIT_INPUT: RESOLVED_UNIT9.of(unit)};
+    return <String, TaskInput>{UNIT_INPUT: RESOLVED_UNIT10.of(unit)};
   }
 
   /**
@@ -2495,7 +2624,7 @@ class GatherUsedLocalElementsTask extends SourceBasedAnalysisTask {
  */
 class GenerateHintsTask extends SourceBasedAnalysisTask {
   /**
-   * The name of the [RESOLVED_UNIT9] input.
+   * The name of the [RESOLVED_UNIT10] input.
    */
   static const String RESOLVED_UNIT_INPUT = 'RESOLVED_UNIT';
 
@@ -2701,7 +2830,7 @@ class InferInstanceMembersInUnitTask extends SourceBasedAnalysisTask {
   static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
 
   /**
-   * The name of the input whose value is the [RESOLVED_UNIT6] for the
+   * The name of the input whose value is the [RESOLVED_UNIT7] for the
    * compilation unit.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
@@ -2713,7 +2842,7 @@ class InferInstanceMembersInUnitTask extends SourceBasedAnalysisTask {
       'InferInstanceMembersInUnitTask',
       createTask,
       buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT8]);
+      <ResultDescriptor>[RESOLVED_UNIT9]);
 
   /**
    * Initialize a newly created task to build a library element for the given
@@ -2744,7 +2873,7 @@ class InferInstanceMembersInUnitTask extends SourceBasedAnalysisTask {
     //
     // Record outputs.
     //
-    outputs[RESOLVED_UNIT8] = unit;
+    outputs[RESOLVED_UNIT9] = unit;
   }
 
   /**
@@ -2755,7 +2884,7 @@ class InferInstanceMembersInUnitTask extends SourceBasedAnalysisTask {
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     LibrarySpecificUnit unit = target;
     return <String, TaskInput>{
-      UNIT_INPUT: RESOLVED_UNIT7.of(unit),
+      UNIT_INPUT: RESOLVED_UNIT8.of(unit),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
       // In strong mode, add additional dependencies to enforce inference
       // ordering.
@@ -2763,12 +2892,12 @@ class InferInstanceMembersInUnitTask extends SourceBasedAnalysisTask {
       // Require that field re-resolution be complete for all units in the
       // current library cycle.
       'orderLibraryCycleTasks': LIBRARY_CYCLE_UNITS.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT7
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT8
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source))),
       // Require that full inference be complete for all dependencies of the
       // current library cycle.
       'orderLibraryCycles': LIBRARY_CYCLE_DEPENDENCIES.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT8
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT9
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source)))
     };
   }
@@ -2816,7 +2945,7 @@ abstract class InferStaticVariableTask extends ConstantEvaluationAnalysisTask {
  */
 class InferStaticVariableTypesInUnitTask extends SourceBasedAnalysisTask {
   /**
-   * The name of the input whose value is the [RESOLVED_UNIT5] for the
+   * The name of the input whose value is the [RESOLVED_UNIT6] for the
    * compilation unit.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
@@ -2834,7 +2963,7 @@ class InferStaticVariableTypesInUnitTask extends SourceBasedAnalysisTask {
       'InferStaticVariableTypesInUnitTask',
       createTask,
       buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT6]);
+      <ResultDescriptor>[RESOLVED_UNIT7]);
 
   /**
    * Initialize a newly created task to build a library element for the given
@@ -2858,7 +2987,7 @@ class InferStaticVariableTypesInUnitTask extends SourceBasedAnalysisTask {
     // because the work has implicitly been done by virtue of the task model
     // preparing all of the inputs.
     //
-    outputs[RESOLVED_UNIT6] = unit;
+    outputs[RESOLVED_UNIT7] = unit;
   }
 
   /**
@@ -2872,7 +3001,7 @@ class InferStaticVariableTypesInUnitTask extends SourceBasedAnalysisTask {
       INFERRED_VARIABLES_INPUT: INFERABLE_STATIC_VARIABLES_IN_UNIT
           .of(unit)
           .toListOf(INFERRED_STATIC_VARIABLE),
-      UNIT_INPUT: RESOLVED_UNIT5.of(unit)
+      UNIT_INPUT: RESOLVED_UNIT6.of(unit)
     };
   }
 
@@ -2903,7 +3032,7 @@ class InferStaticVariableTypeTask extends InferStaticVariableTask {
   static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
 
   /**
-   * The name of the [RESOLVED_UNIT5] input.
+   * The name of the [RESOLVED_UNIT6] input.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
 
@@ -3001,14 +3130,14 @@ class InferStaticVariableTypeTask extends InferStaticVariableTask {
           .of(variable)
           .toListOf(INFERRED_STATIC_VARIABLE),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
-      UNIT_INPUT: RESOLVED_UNIT5.of(unit),
+      UNIT_INPUT: RESOLVED_UNIT6.of(unit),
       // In strong mode, add additional dependencies to enforce inference
       // ordering.
 
       // Require that full inference be complete for all dependencies of the
       // current library cycle.
       'orderLibraryCycles': LIBRARY_CYCLE_DEPENDENCIES.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT8
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT9
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source)))
     };
   }
@@ -3418,8 +3547,11 @@ class PartiallyResolveUnitReferencesTask extends SourceBasedAnalysisTask {
   static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
       'PartiallyResolveUnitReferencesTask',
       createTask,
-      buildInputs,
-      <ResultDescriptor>[INFERABLE_STATIC_VARIABLES_IN_UNIT, RESOLVED_UNIT5]);
+      buildInputs, <ResultDescriptor>[
+    INFERABLE_STATIC_VARIABLES_IN_UNIT,
+    PROPAGABLE_VARIABLES_IN_UNIT,
+    RESOLVED_UNIT5
+  ]);
 
   PartiallyResolveUnitReferencesTask(
       InternalAnalysisContext context, AnalysisTarget target)
@@ -3440,21 +3572,21 @@ class PartiallyResolveUnitReferencesTask extends SourceBasedAnalysisTask {
     //
     // Resolve references and record outputs.
     //
+    InheritanceManager inheritanceManager =
+        new InheritanceManager(libraryElement);
+    PartialResolverVisitor visitor = new PartialResolverVisitor(libraryElement,
+        unitElement.source, typeProvider, AnalysisErrorListener.NULL_LISTENER,
+        inheritanceManager: inheritanceManager);
+    unit.accept(visitor);
+    //
+    // Record outputs.
+    //
     if (context.analysisOptions.strongMode) {
-      InheritanceManager inheritanceManager =
-          new InheritanceManager(libraryElement);
-      PartialResolverVisitor visitor = new PartialResolverVisitor(
-          libraryElement,
-          unitElement.source,
-          typeProvider,
-          AnalysisErrorListener.NULL_LISTENER,
-          inheritanceManager: inheritanceManager);
-      unit.accept(visitor);
-
-      outputs[INFERABLE_STATIC_VARIABLES_IN_UNIT] = visitor.variablesAndFields;
+      outputs[INFERABLE_STATIC_VARIABLES_IN_UNIT] = visitor.staticVariables;
     } else {
-      outputs[INFERABLE_STATIC_VARIABLES_IN_UNIT] = [];
+      outputs[INFERABLE_STATIC_VARIABLES_IN_UNIT] = VariableElement.EMPTY_LIST;
     }
+    outputs[PROPAGABLE_VARIABLES_IN_UNIT] = visitor.propagableVariables;
     outputs[RESOLVED_UNIT5] = unit;
   }
 
@@ -3476,7 +3608,7 @@ class PartiallyResolveUnitReferencesTask extends SourceBasedAnalysisTask {
       // Require that full inference be complete for all dependencies of the
       // current library cycle.
       'orderLibraryCycles': LIBRARY_CYCLE_DEPENDENCIES.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT8
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT9
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source)))
     };
   }
@@ -3492,6 +3624,174 @@ class PartiallyResolveUnitReferencesTask extends SourceBasedAnalysisTask {
 }
 
 /**
+ * A task that ensures that all of the propagable variables in a compilation
+ * unit have had their type propagated.
+ */
+class PropagateVariableTypesInUnitTask extends SourceBasedAnalysisTask {
+  /**
+   * The name of the input whose value is the [RESOLVED_UNIT5] for the
+   * compilation unit.
+   */
+  static const String UNIT_INPUT = 'UNIT_INPUT';
+
+  /**
+   * The task descriptor describing this kind of task.
+   */
+  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
+      'PropagateVariableTypesInUnitTask',
+      createTask,
+      buildInputs,
+      <ResultDescriptor>[RESOLVED_UNIT6]);
+
+  PropagateVariableTypesInUnitTask(
+      InternalAnalysisContext context, LibrarySpecificUnit unit)
+      : super(context, unit);
+
+  @override
+  TaskDescriptor get descriptor => DESCRIPTOR;
+
+  @override
+  void internalPerform() {
+    //
+    // Prepare inputs.
+    //
+    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
+    //
+    // Record outputs. There is no additional work to be done at this time
+    // because the work has implicitly been done by virtue of the task model
+    // preparing all of the inputs.
+    //
+    outputs[RESOLVED_UNIT6] = unit;
+  }
+
+  /**
+   * 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) {
+    LibrarySpecificUnit unit = target;
+    return <String, TaskInput>{
+      'variables':
+          PROPAGABLE_VARIABLES_IN_UNIT.of(unit).toListOf(PROPAGATED_VARIABLE),
+      UNIT_INPUT: RESOLVED_UNIT5.of(unit)
+    };
+  }
+
+  /**
+   * Create a [PropagateVariableTypesInUnitTask] based on the given [target]
+   * in the given [context].
+   */
+  static PropagateVariableTypesInUnitTask createTask(
+      AnalysisContext context, AnalysisTarget target) {
+    return new PropagateVariableTypesInUnitTask(context, target);
+  }
+}
+
+/**
+ * A task that computes the propagated type of an propagable variable and
+ * stores it in the element model.
+ */
+class PropagateVariableTypeTask extends InferStaticVariableTask {
+  /**
+   * The name of the [TYPE_PROVIDER] input.
+   */
+  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
+
+  /**
+   * The name of the [RESOLVED_UNIT5] input.
+   */
+  static const String UNIT_INPUT = 'UNIT_INPUT';
+
+  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
+      'PropagateVariableTypeTask',
+      createTask,
+      buildInputs,
+      <ResultDescriptor>[PROPAGATED_VARIABLE]);
+
+  PropagateVariableTypeTask(
+      InternalAnalysisContext context, VariableElement variable)
+      : super(context, variable);
+
+  @override
+  TaskDescriptor get descriptor => DESCRIPTOR;
+
+  @override
+  bool get handlesDependencyCycles => true;
+
+  @override
+  void internalPerform() {
+    //
+    // Prepare inputs.
+    //
+    PropertyInducingElementImpl variable = target;
+    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
+    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
+
+    // If we're not in a dependency cycle, and we have no type annotation,
+    // re-resolve the right hand side and do inference.
+    if (dependencyCycle == null && variable.hasImplicitType) {
+      VariableDeclaration declaration = getDeclaration(unit);
+      //
+      // Re-resolve the variable's initializer so that the inferred types

[Brian Wilkerson, 2015/11/21 15:11:26]

"inferred" --> "propagated"?

+      // of other variables will be propagated.
+      //
+      Expression initializer = declaration.initializer;
+      ResolutionContext resolutionContext = ResolutionContextBuilder.contextFor(
+          initializer, AnalysisErrorListener.NULL_LISTENER);
+      ResolverVisitor visitor = new ResolverVisitor(variable.library,
+          variable.source, typeProvider, AnalysisErrorListener.NULL_LISTENER,
+          nameScope: resolutionContext.scope);
+      if (resolutionContext.enclosingClassDeclaration != null) {
+        visitor.prepareToResolveMembersInClass(
+            resolutionContext.enclosingClassDeclaration);
+      }
+      visitor.initForIncrementalResolution();
+      initializer.accept(visitor);
+      //
+      // Record the type of the variable.
+      //
+      DartType newType = initializer.bestType;

[Brian Wilkerson, 2015/11/21 15:11:26]

I think this wants to be the propagatedType, not the best type. Otherwise we
could end up recording the static type as the propagated type, which I don't
think we want to do.

[scheglov, 2015/11/21 17:37:23]

Actually in the most cases the initializer is a value with a static type only,
for example:

final a = 42;

Here "42" has only static type - int.
And yes, we record it as a propagated type.


But if have also:

final b = a;

Then "a" here has staticType==dynamic and propagatedType==int.
So, we use the "bestType", which is "int".

+      if (newType == null || newType.isBottom || newType.isDynamic) {
+        newType = null;
+      }
+      variable.propagatedType = newType;
+    }
+    //
+    // Record outputs.
+    //
+    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;
+    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),
+    };
+  }
+
+  /**
+   * Create a [PropagateVariableTypeTask] based on the given [target] in the
+   * given [context].
+   */
+  static PropagateVariableTypeTask createTask(
+      AnalysisContext context, AnalysisTarget target) {
+    return new PropagateVariableTypeTask(context, target);
+  }
+}
+
+/**
  * The helper for building the public [Namespace] of a [LibraryElement].
  */
 class PublicNamespaceBuilder {
@@ -3617,7 +3917,7 @@ class ReadyLibraryElement5Task extends SourceBasedAnalysisTask {
 }
 
 /**
- * A task that ensures that [RESOLVED_UNIT10] is ready for every unit of the
+ * A task that ensures that [RESOLVED_UNIT11] is ready for every unit of the
  * target library source and its import/export closure.
  */
 class ReadyResolvedUnit10Task extends SourceBasedAnalysisTask {
@@ -3646,7 +3946,7 @@ class ReadyResolvedUnit10Task extends SourceBasedAnalysisTask {
     Source source = target;
     return <String, TaskInput>{
       'thisLibraryUnitsReady':
-          LIBRARY_SPECIFIC_UNITS.of(source).toListOf(RESOLVED_UNIT10),
+          LIBRARY_SPECIFIC_UNITS.of(source).toListOf(RESOLVED_UNIT11),
       'directlyImportedLibrariesReady':
           IMPORTED_LIBRARIES.of(source).toListOf(READY_RESOLVED_UNIT10),
       'directlyExportedLibrariesReady':
@@ -3661,7 +3961,7 @@ class ReadyResolvedUnit10Task extends SourceBasedAnalysisTask {
 }
 
 /**
- * A task that ensures that [RESOLVED_UNIT9] is ready for every unit of the
+ * A task that ensures that [RESOLVED_UNIT10] is ready for every unit of the
  * target library source and its import/export closure.
  */
 class ReadyResolvedUnit9Task extends SourceBasedAnalysisTask {
@@ -3689,7 +3989,7 @@ class ReadyResolvedUnit9Task extends SourceBasedAnalysisTask {
     Source source = target;
     return <String, TaskInput>{
       'thisLibraryUnitsReady':
-          LIBRARY_SPECIFIC_UNITS.of(source).toListOf(RESOLVED_UNIT9),
+          LIBRARY_SPECIFIC_UNITS.of(source).toListOf(RESOLVED_UNIT10),
       'directlyImportedLibrariesReady':
           IMPORTED_LIBRARIES.of(source).toListOf(READY_RESOLVED_UNIT9),
       'directlyExportedLibrariesReady':
@@ -3860,7 +4160,7 @@ class ResolveInstanceFieldsInUnitTask extends SourceBasedAnalysisTask {
   static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
 
   /**
-   * The name of the input whose value is the [RESOLVED_UNIT6] for the
+   * The name of the input whose value is the [RESOLVED_UNIT7] for the
    * compilation unit.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
@@ -3872,7 +4172,7 @@ class ResolveInstanceFieldsInUnitTask extends SourceBasedAnalysisTask {
       'ResolveInstanceFieldsInUnitTask',
       createTask,
       buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT7]);
+      <ResultDescriptor>[RESOLVED_UNIT8]);
 
   /**
    * Initialize a newly created task to build a library element for the given
@@ -3920,7 +4220,7 @@ class ResolveInstanceFieldsInUnitTask extends SourceBasedAnalysisTask {
     //
     // Record outputs.
     //
-    outputs[RESOLVED_UNIT7] = unit;
+    outputs[RESOLVED_UNIT8] = unit;
   }
 
   /**
@@ -3931,7 +4231,7 @@ class ResolveInstanceFieldsInUnitTask extends SourceBasedAnalysisTask {
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     LibrarySpecificUnit unit = target;
     return <String, TaskInput>{
-      UNIT_INPUT: RESOLVED_UNIT6.of(unit),
+      UNIT_INPUT: RESOLVED_UNIT7.of(unit),
       LIBRARY_INPUT: LIBRARY_ELEMENT5.of(unit.library),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
       // In strong mode, add additional dependencies to enforce inference
@@ -3940,12 +4240,12 @@ class ResolveInstanceFieldsInUnitTask extends SourceBasedAnalysisTask {
       // Require that static variable inference  be complete for all units in
       // the current library cycle.
       'orderLibraryCycleTasks': LIBRARY_CYCLE_UNITS.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT6
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT7
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source))),
       // Require that full inference be complete for all dependencies of the
       // current library cycle.
       'orderLibraryCycles': LIBRARY_CYCLE_DEPENDENCIES.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT8
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT9
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source)))
     };
   }
@@ -3961,7 +4261,7 @@ class ResolveInstanceFieldsInUnitTask extends SourceBasedAnalysisTask {
 }
 
 /**
- * A task that finishes resolution by requesting [RESOLVED_UNIT9] for every
+ * A task that finishes resolution by requesting [RESOLVED_UNIT10] for every
  * unit in the libraries closure and produces [LIBRARY_ELEMENT].
  */
 class ResolveLibraryReferencesTask extends SourceBasedAnalysisTask {
@@ -3971,7 +4271,7 @@ class ResolveLibraryReferencesTask extends SourceBasedAnalysisTask {
   static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
 
   /**
-   * The name of the list of [RESOLVED_UNIT9] input.
+   * The name of the list of [RESOLVED_UNIT10] input.
    */
   static const String UNITS_INPUT = 'UNITS_INPUT';
 
@@ -4019,7 +4319,7 @@ class ResolveLibraryReferencesTask extends SourceBasedAnalysisTask {
     Source source = target;
     return <String, TaskInput>{
       LIBRARY_INPUT: LIBRARY_ELEMENT5.of(source),
-      UNITS_INPUT: LIBRARY_SPECIFIC_UNITS.of(source).toListOf(RESOLVED_UNIT9),
+      UNITS_INPUT: LIBRARY_SPECIFIC_UNITS.of(source).toListOf(RESOLVED_UNIT10),
       'thisLibraryClosureIsReady': READY_RESOLVED_UNIT9.of(source),
     };
   }
@@ -4123,7 +4423,7 @@ class ResolveUnitTask extends SourceBasedAnalysisTask {
   static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
 
   /**
-   * The name of the [RESOLVED_UNIT8] input.
+   * The name of the [RESOLVED_UNIT9] input.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
 
@@ -4131,7 +4431,7 @@ class ResolveUnitTask extends SourceBasedAnalysisTask {
       'ResolveUnitTask',
       createTask,
       buildInputs,
-      <ResultDescriptor>[RESOLVE_UNIT_ERRORS, RESOLVED_UNIT9]);
+      <ResultDescriptor>[RESOLVE_UNIT_ERRORS, RESOLVED_UNIT10]);
 
   ResolveUnitTask(
       InternalAnalysisContext context, LibrarySpecificUnit compilationUnit)
@@ -4164,7 +4464,7 @@ class ResolveUnitTask extends SourceBasedAnalysisTask {
     // updated version of the element model.
     //
     outputs[RESOLVE_UNIT_ERRORS] = errorListener.errors;
-    outputs[RESOLVED_UNIT9] = unit;
+    outputs[RESOLVED_UNIT10] = unit;
   }
 
   /**
@@ -4177,14 +4477,14 @@ class ResolveUnitTask extends SourceBasedAnalysisTask {
     return <String, TaskInput>{
       LIBRARY_INPUT: LIBRARY_ELEMENT5.of(unit.library),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
-      UNIT_INPUT: RESOLVED_UNIT8.of(unit),
+      UNIT_INPUT: RESOLVED_UNIT9.of(unit),
       // In strong mode, add additional dependencies to enforce inference
       // ordering.
 
       // Require that inference be complete for all units in the
       // current library cycle.
       'orderLibraryCycleTasks': LIBRARY_CYCLE_UNITS.of(unit).toList(
-          (CompilationUnitElementImpl unit) => RESOLVED_UNIT8
+          (CompilationUnitElementImpl unit) => RESOLVED_UNIT9
               .of(new LibrarySpecificUnit(unit.librarySource, unit.source)))
     };
   }
@@ -4493,7 +4793,7 @@ class ScanDartTask extends SourceBasedAnalysisTask {
  */
 class StrongModeVerifyUnitTask extends SourceBasedAnalysisTask {
   /**
-   * The name of the [RESOLVED_UNIT10] input.
+   * The name of the [RESOLVED_UNIT11] input.
    */
   static const String UNIT_INPUT = 'UNIT_INPUT';
 
@@ -4545,7 +4845,7 @@ class StrongModeVerifyUnitTask extends SourceBasedAnalysisTask {
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     LibrarySpecificUnit unit = target;
     return <String, TaskInput>{
-      UNIT_INPUT: RESOLVED_UNIT10.of(unit),
+      UNIT_INPUT: RESOLVED_UNIT11.of(unit),
       TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
       'thisLibraryClosureIsReady': READY_RESOLVED_UNIT10.of(unit.library),
     };