Fix type inference of getters that "override" setters and vice versa.

pkg/front_end/lib/src/fasta/type_inference/type_inference_engine.dart

 // Copyright (c) 2017, 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.md file.
 
 import 'package:front_end/src/base/instrumentation.dart';
 import 'package:front_end/src/dependency_walker.dart' as dependencyWalker;
 import 'package:front_end/src/fasta/errors.dart';
 import 'package:front_end/src/fasta/kernel/kernel_shadow_ast.dart';
 import 'package:front_end/src/fasta/type_inference/type_inference_listener.dart';
 import 'package:front_end/src/fasta/type_inference/type_inferrer.dart';
@@ skipping 21 matching lines @@
 
   /// If [state] is [FieldState.Inferring], and type inference for this field
   /// is waiting on type inference of some other field, the field that is being
   /// waited on.
   ///
   /// Otherwise `null`.
   FieldNode currentDependency;
 
   final overrides = <Member>[];
 
+  final crossOverrides = <Member>[];
+
   FieldNode(this._typeInferenceEngine, this.member);
 
+  get candidateOverrides => overrides.isNotEmpty ? overrides : crossOverrides;
+
   @override
   bool get isEvaluated => state == FieldState.Inferred;
 
   @override
   List<FieldNode> computeDependencies() {
     return _typeInferenceEngine.computeFieldDependencies(this);
   }
 
   @override
   String toString() => member.toString();
@@ skipping 97 matching lines @@
   ClassHierarchy classHierarchy;
 
   TypeSchemaEnvironment typeSchemaEnvironment;
 
   TypeInferenceEngineImpl(this.instrumentation, this.strongMode);
 
   /// Computes type inference dependencies for the given [field].
   List<FieldNode> computeFieldDependencies(FieldNode fieldNode) {
     // If the field's type is going to be determined by inheritance, then its
     // dependencies are determined by inheritance too.
-    if (fieldNode.overrides.isNotEmpty) {
+    var candidateOverrides = fieldNode.candidateOverrides;
+    if (candidateOverrides.isNotEmpty) {
       var dependencies = <FieldNode>[];
-      for (var override in fieldNode.overrides) {
-        // TODO(paulberry): support dependencies on getters/setters too.
+      for (var override in candidateOverrides) {
         var dep = KernelMember.getFieldNode(override);
         if (dep != null) dependencies.add(dep);
       }
       fieldNode.isImmediatelyEvident = true;
       return dependencies;
     }
 
     // Otherwise its dependencies are based on the initializer expression.
     var member = fieldNode.member;
     if (member is KernelField) {
@@ skipping 153 matching lines @@
     initializingFormals.add(formal);
   }
 
   @override
   void recordMember(KernelMember member) {
     fieldNodes.add(createFieldNode(member));
   }
 
   DartType tryInferFieldByInheritance(FieldNode fieldNode) {
     DartType inferredType;
-    for (var override in fieldNode.overrides) {
+    for (var override in fieldNode.candidateOverrides) {
       var nextInferredType = _computeOverriddenFieldType(override, fieldNode);
       if (inferredType == null) {
         inferredType = nextInferredType;
       } else if (inferredType != nextInferredType) {
         // Overrides don't have matching types.
         // TODO(paulberry): report an error
         return const DynamicType();
       }
     }
     return inferredType;
@@ skipping 56 matching lines @@
   }
 
   @override
   void evaluateScc(List<FieldNode> scc) {
     // Mark every field as part of a circularity.
     for (var f in scc) {
       f._typeInferenceEngine.inferFieldCircular(f);
     }
   }
 }