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

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

Index: pkg/front_end/lib/src/fasta/type_inference/type_inference_engine.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inference_engine.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inference_engine.dart
index ee4166216ede6c53cb54d942acab19886ed6dfb4..54d61a4acb0d0c949a700bc56bb801bf929cbdf0 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inference_engine.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inference_engine.dart
@@ -39,8 +39,12 @@ class FieldNode extends dependencyWalker.Node<FieldNode> {
 
   final overrides = <Member>[];
 
+  final crossOverrides = <Member>[];
+
   FieldNode(this._typeInferenceEngine, this.member);
 
+  get candidateOverrides => overrides.isNotEmpty ? overrides : crossOverrides;
+
   @override
   bool get isEvaluated => state == FieldState.Inferred;
 
@@ -158,10 +162,10 @@ abstract class TypeInferenceEngineImpl extends TypeInferenceEngine {
   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);
       }
@@ -335,7 +339,7 @@ abstract class TypeInferenceEngineImpl extends TypeInferenceEngine {
 
   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;