Create synthetic FieldElement(s) (don't use non-synthetic ones) for non-synthetic class getters/set…

pkg/analyzer/test/src/context/context_test.dart

Index: pkg/analyzer/test/src/context/context_test.dart
diff --git a/pkg/analyzer/test/src/context/context_test.dart b/pkg/analyzer/test/src/context/context_test.dart
index 8c13cf569645406e1f213248c0d45fa8cc6ae762..749edcee66eeb2a852f596956dfd09c8d1f05bc4 100644
--- a/pkg/analyzer/test/src/context/context_test.dart
+++ b/pkg/analyzer/test/src/context/context_test.dart
@@ -3927,6 +3927,40 @@ const A = 2;
     _assertInvalid(d, LIBRARY_ERRORS_READY);
   }
 
+  void test_sequence_duplicateField_syntheticAndNot_renameNotSynthetic() {
+    context.analysisOptions =
+        new AnalysisOptionsImpl.from(context.analysisOptions)
+          ..strongMode = true;
+    Source a = addSource(
+        '/a.dart',
+        r'''
+class A {
+  int foo;
+  int get foo => 1;
+}
+class B extends A {
+  int get foo => 2;
+}
+''');
+    _performPendingAnalysisTasks();
+    expect(context.getErrors(a).errors, hasLength(2));
+    // Update a.dart: rename "int foo" to "int bar".
+    // The strong mode "getter cannot override field" error is gone.
+    context.setContents(
+        a,
+        r'''
+class A {
+  int bar;
+  int get foo => 1;
+}
+class B extends A {
+  int get foo => 2;
+}
+''');
+    _performPendingAnalysisTasks();
+    expect(context.getErrors(a).errors, isEmpty);
+  }
+
   void test_sequence_inBodyChange_addRef_deltaChange() {
     Source a = addSource(
         '/a.dart',