Stop using Element.unit directly.

pkg/analysis_server/lib/src/edit/edit_domain.dart

 // Copyright (c) 2014, 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 file.
 
 library edit.domain;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/edit/assist/assist_core.dart';
 import 'package:analysis_server/plugin/edit/assist/assist_dart.dart';
@@ skipping 385 matching lines @@
     if (length != 0) {
       kinds.add(RefactoringKind.EXTRACT_LOCAL_VARIABLE);
       kinds.add(RefactoringKind.EXTRACT_METHOD);
     }
     // check elements
     {
       Element element = await server.getElementAtOffset(file, offset);
       if (element != null) {
         // try CONVERT_METHOD_TO_GETTER
         if (element is ExecutableElement) {
-          Refactoring refactoring =
-              new ConvertMethodToGetterRefactoring(searchEngine, element);
+          Refactoring refactoring = new ConvertMethodToGetterRefactoring(
+              searchEngine,
+              (element) =>
+                  throw new StateError('Unexpected resolved unit request.'),

[Brian Wilkerson, 2016/11/30 17:34:18]

I guess this is fine, but I was thinking of passing a non-exception-throwing
function in here.

On closer inspection, however, I see that you don't have ready access to such a
function. You'd either have to duplicate '_getResolvedUnit' (from line 690) or
create a global utility method such as

GetResolvedUnit getResolvedUnitGetter(AnalysisServer server) => (Element
element) {
  String path = element.source.fullName;
  return server.getResolvedCompilationUnit(path);
};

Probably not worth it.

+              element);
           RefactoringStatus status = await refactoring.checkInitialConditions();
           if (!status.hasFatalError) {
             kinds.add(RefactoringKind.CONVERT_METHOD_TO_GETTER);
           }
         }
         // try RENAME
         {
           RenameRefactoring renameRefactoring =
               new RenameRefactoring(searchEngine, element);
           if (renameRefactoring != null) {
@@ skipping 259 matching lines @@
 
   void _checkForReset_afterInitialConditions() {
     if (test_simulateRefactoringReset_afterInitialConditions) {
       _reset();
     }
     if (refactoring == null) {
       throw new _ResetError();
     }
   }
 
+  Future<CompilationUnit> _getResolvedUnit(Element element) {
+    String path = element.source.fullName;
+    return server.getResolvedCompilationUnit(path);
+  }
+
   /**
    * Initializes this context to perform a refactoring with the specified
    * parameters. The existing [Refactoring] is reused or created as needed.
    */
   Future _init(
       RefactoringKind kind, String file, int offset, int length) async {
     await _analyzeForRefactoring(file, kind);
     // check if we can continue with the existing Refactoring instance
     if (this.kind == kind &&
         this.file == file &&
@@ skipping 19 matching lines @@
           refactoring =
               new ConvertGetterToMethodRefactoring(searchEngine, element);
         }
       }
     }
     if (kind == RefactoringKind.CONVERT_METHOD_TO_GETTER) {
       Element element = await server.getElementAtOffset(file, offset);
       if (element != null) {
         if (element is ExecutableElement) {
           _resetOnAnalysisStarted();
-          refactoring =
-              new ConvertMethodToGetterRefactoring(searchEngine, element);
+          refactoring = new ConvertMethodToGetterRefactoring(
+              searchEngine, _getResolvedUnit, element);
         }
       }
     }
     if (kind == RefactoringKind.EXTRACT_LOCAL_VARIABLE) {
       CompilationUnit unit = await server.getResolvedCompilationUnit(file);
       if (unit != null) {
         _resetOnFileResolutionChanged(file);
         refactoring = new ExtractLocalRefactoring(unit, offset, length);
         feedback = new ExtractLocalVariableFeedback(
             <String>[], <int>[], <int>[],
@@ skipping 15 matching lines @@
       CompilationUnit unit = await server.getResolvedCompilationUnit(file);
       if (unit != null) {
         _resetOnFileResolutionChanged(file);
         refactoring = new InlineLocalRefactoring(searchEngine, unit, offset);
       }
     }
     if (kind == RefactoringKind.INLINE_METHOD) {
       CompilationUnit unit = await server.getResolvedCompilationUnit(file);
       if (unit != null) {
         _resetOnAnalysisStarted();
-        refactoring =
-            new InlineMethodRefactoring(searchEngine, (Element element) async {
-          String elementPath = element.source.fullName;
-          return await server.getResolvedCompilationUnit(elementPath);
-        }, unit, offset);
+        refactoring = new InlineMethodRefactoring(
+            searchEngine, _getResolvedUnit, unit, offset);
       }
     }
     if (kind == RefactoringKind.MOVE_FILE) {
       _resetOnAnalysisStarted();
       ContextSourcePair contextSource = server.getContextSourcePair(file);
       engine.AnalysisContext context = contextSource.context;
       Source source = contextSource.source;
       refactoring = new MoveFileRefactoring(
           server.resourceProvider, searchEngine, context, source, file);
     }
@@ skipping 168 matching lines @@
     }
     return new RefactoringStatus();
   }
 }
 
 /**
  * [_RefactoringManager] throws instances of this class internally to stop
  * processing in a manager that was reset.
  */
 class _ResetError {}