Test for changing method to/from getter/setter.

pkg/analyzer/lib/src/generated/incremental_resolver.dart

Index: pkg/analyzer/lib/src/generated/incremental_resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/incremental_resolver.dart b/pkg/analyzer/lib/src/generated/incremental_resolver.dart
index f767db283f0a9650cea4fd82c0ace50116a2e68e..b67b90552ca24c276c23451cc395685aaa95ec76 100644
--- a/pkg/analyzer/lib/src/generated/incremental_resolver.dart
+++ b/pkg/analyzer/lib/src/generated/incremental_resolver.dart
@@ -357,11 +357,12 @@ class DeclarationMatcher extends RecursiveAstVisitor {
       if (newElement != null) {
         _addedElements.add(newElement);
         if (newElement is MethodElement) {
-          List<MethodElement> methods = _enclosingClass.methods;
+          List<MethodElement> methods = _enclosingClass.methods.toList();
           methods.add(newElement);
           _enclosingClass.methods = methods;
         } else {
-          List<PropertyAccessorElement> accessors = _enclosingClass.accessors;
+          List<PropertyAccessorElement> accessors =
+              _enclosingClass.accessors.toList();
           accessors.add(newElement);
           _enclosingClass.accessors = accessors;
         }