Fix cache corruption in incremental resolver

pkg/analyzer/test/generated/incremental_resolver_test.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 analyzer.test.generated.incremental_resolver_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/context/cache.dart';
@@ skipping 3483 matching lines @@
     // resolve "newCode" from scratch
     CompilationUnit fullNewUnit;
     {
       source = addSource(newCode);
       _runTasks();
       LibraryElement library = resolve2(source);
       fullNewUnit = resolveCompilationUnit(source, library);
     }
     _checkCacheEntries(cache);
 
-    try {
-      assertSameResolution(unit, fullNewUnit);
-    } on IncrementalResolutionMismatch catch (mismatch) {
-      fail(mismatch.message);
-    }
+    assertSameResolution(unit, fullNewUnit);
     // errors
     List<AnalysisError> newFullErrors =
         analysisContext.getErrors(source).errors;
     _assertEqualErrors(newErrors, newFullErrors);
     // prepare for the next cycle
     code = newCode;
   }
 
   void _resolveUnit(String code) {
     this.code = code;
@@ skipping 1323 matching lines @@
     {
       ClassElement typeA = oldUnitElement.getType('A');
       expect(oldUnitElement.getElementAt(typeA.nameOffset), typeA);
     }
     {
       ClassElement typeB = oldUnitElement.getType('B');
       expect(oldUnitElement.getElementAt(typeB.nameOffset), typeB);
     }
   }
 
-  void _assertCacheResults({bool expectCachePostConstantsValid: true}) {
+  void test_updateFunctionToForLoop() {
+    _resolveUnit(r'''
+class PlayDrag {
+  final List<num> times = new List<num>();
+
+  PlayDrag.start() {}
+
+  void update(num pos) {
+    fo (int i = times.length - 2; i >= 0; i--) {}
+  }
+}
+''');
+
+    _updateAndValidate(
+        r'''
+class PlayDrag {
+  final List<num> times = new List<num>();
+
+  PlayDrag.start() {}
+
+  void update(num pos) {
+    for (int i = times.length - 2; i >= 0; i--) {}
+  }
+}
+''',
+        expectLibraryUnchanged: false);
+  }
+
+  void _assertCacheResults(
+      {bool expectLibraryUnchanged: true,
+      bool expectCachePostConstantsValid: true}) {
     _assertCacheSourceResult(TOKEN_STREAM);
     _assertCacheSourceResult(SCAN_ERRORS);
     _assertCacheSourceResult(PARSED_UNIT);
     _assertCacheSourceResult(PARSE_ERRORS);
+    if (!expectLibraryUnchanged) {
+      return;
+    }
     _assertCacheSourceResult(LIBRARY_ELEMENT1);
     _assertCacheSourceResult(LIBRARY_ELEMENT2);
     _assertCacheSourceResult(LIBRARY_ELEMENT3);
     _assertCacheSourceResult(LIBRARY_ELEMENT4);
     _assertCacheSourceResult(LIBRARY_ELEMENT5);
     _assertCacheSourceResult(LIBRARY_ELEMENT6);
     _assertCacheSourceResult(LIBRARY_ELEMENT7);
     _assertCacheSourceResult(LIBRARY_ELEMENT8);
     if (expectCachePostConstantsValid) {
       _assertCacheSourceResult(LIBRARY_ELEMENT);
@@ skipping 69 matching lines @@
 
   void _runTasks() {
     AnalysisResult result = analysisContext.performAnalysisTask();
     while (result.changeNotices != null) {
       result = analysisContext.performAnalysisTask();
     }
   }
 
   void _updateAndValidate(String newCode,
       {bool expectedSuccess: true,
+      bool expectLibraryUnchanged: true,
       bool expectCachePostConstantsValid: true,
       bool compareWithFull: true,
       bool runTasksBeforeIncremental: true}) {
     // Run any pending tasks tasks.
     if (runTasksBeforeIncremental) {
       _runTasks();
     }
     // Update the source - currently this may cause incremental resolution.
     // Then request the updated resolved unit.
     _resetWithIncremental(true);
     analysisContext2.setContents(source, newCode);
     CompilationUnit newUnit = resolveCompilationUnit(source, oldLibrary);
-    expect(logger.hasError, isFalse);
+    if (logger.hasError) {
+      fail("logged an error: ${logger.lastError}");
+    }
     List<AnalysisError> newErrors = analysisContext.computeErrors(source);
     LineInfo newLineInfo = analysisContext.getLineInfo(source);
     // check for expected failure
     if (!expectedSuccess) {
       expect(newUnit.element, isNot(same(oldUnitElement)));
       return;
     }
     // The cache must still have enough results to make the incremental
     // resolution useful.
     _assertCacheResults(
+        expectLibraryUnchanged: expectLibraryUnchanged,
         expectCachePostConstantsValid: expectCachePostConstantsValid);
     // The existing CompilationUnit[Element] should be updated.
     expect(newUnit, same(oldUnit));
     expect(newUnit.element, same(oldUnitElement));
     expect(analysisContext.getResolvedCompilationUnit(source, oldLibrary),
         same(oldUnit));
     // The only expected pending task should return the same resolved
     // "newUnit", so all clients will get it using the usual way.
     AnalysisResult analysisResult = analysisContext.performAnalysisTask();
     ChangeNotice notice = analysisResult.changeNotices[0];
@@ skipping 269 matching lines @@
 }
 
 class _Edit {
   final int offset;
   final int length;
   final String replacement;
   _Edit(this.offset, this.length, this.replacement);
 }
 
 class _TestLogger implements logging.Logger {
-  bool hasError = false;
+  Object lastError;
+
+  bool get hasError => lastError != null;
 
   @override
   void enter(String name) {}
 
   @override
   void exit() {}
 
   @override
   void log(Object obj) {}
 
   @override
   void logException(Object exception, [Object stackTrace]) {
-    hasError = true;
+    lastError = exception;

[Brian Wilkerson, 2016/02/16 15:10:48]

Seems like it would be useful to also capture the stack trace so that we could
include it in the failure message. Also, perhaps replace `hasError` with an
`expectNoErrors` method that calls `fail` directly because that would ensure
that we're always including the extra debugging information.

[skybrian, 2016/02/17 01:23:41]

Done.

   }
 
   @override
   logging.LoggingTimer startTimer() {
     return new logging.LoggingTimer(this);
   }
 }