Issue 26629. Detect cache inconsistency in GetContentTask.

pkg/analyzer/lib/task/model.dart

Index: pkg/analyzer/lib/task/model.dart
diff --git a/pkg/analyzer/lib/task/model.dart b/pkg/analyzer/lib/task/model.dart
index dd1062fc9f067fe46da68cdb94428656c1d56b27..be39c04335521bc5a7a18535aba50857bd51c59c 100644
--- a/pkg/analyzer/lib/task/model.dart
+++ b/pkg/analyzer/lib/task/model.dart
@@ -335,6 +335,8 @@ abstract class AnalysisTask {
 //      }
     } on AnalysisException {
       rethrow;
+    } on ModificationTimeMismatchError {
+      rethrow;
     } catch (exception, stackTrace) {
       throw new AnalysisException(
           'Unexpected exception while performing $description',
@@ -423,6 +425,18 @@ abstract class MapTaskInput<K, V> implements TaskInput<Map<K, V>> {
 }
 
 /**
+ * Instances of this class are thrown when a task detects that the modification
+ * time of a cache entry is not the same as the actual modification time.  This
+ * means that any analysis results based on the content of the target cannot be
+ * used anymore and must be invalidated.
+ */
+class ModificationTimeMismatchError {
+  final AnalysisTarget target;

[Brian Wilkerson, 2016/06/08 22:21:55]

I suspect this will always be a Source, but the extra generality might not be a
problem.

+
+  ModificationTimeMismatchError(this.target);
+}
+
+/**
  * A policy object that can compute sizes of results and provide the maximum
  * active and idle sizes that can be kept in the cache.
  *