Initial version of limiting invalidation.

pkg/analyzer/lib/src/context/cache.dart

Index: pkg/analyzer/lib/src/context/cache.dart
diff --git a/pkg/analyzer/lib/src/context/cache.dart b/pkg/analyzer/lib/src/context/cache.dart
index 0b93d03743b899c6b99864b1119d9b8443f2ab73..662e350532e63cc365deef3ba738922113b38fff 100644
--- a/pkg/analyzer/lib/src/context/cache.dart
+++ b/pkg/analyzer/lib/src/context/cache.dart
@@ -412,7 +412,7 @@ class CacheEntry {
    * Set the state of the result represented by the given [descriptor] to the
    * given [state].
    */
-  void setState(ResultDescriptor descriptor, CacheState state) {
+  void setState(ResultDescriptor descriptor, CacheState state, {Delta delta}) {
     if (state == CacheState.ERROR) {
       throw new ArgumentError('use setErrorState() to set the state to ERROR');
     }
@@ -423,7 +423,7 @@ class CacheEntry {
     if (state == CacheState.INVALID) {
       ResultData data = _resultMap[descriptor];
       if (data != null) {
-        _invalidate(descriptor);
+        _invalidate(descriptor, delta);
       }
     } else {
       ResultData data = getResultData(descriptor);
@@ -471,7 +471,7 @@ class CacheEntry {
   void setValueIncremental(ResultDescriptor descriptor, dynamic value) {
     ResultData data = getResultData(descriptor);
     List<TargetedResult> dependedOn = data.dependedOnResults;
-    _invalidate(descriptor);
+    _invalidate(descriptor, null);
     setValue(descriptor, value, dependedOn);
   }
 
@@ -491,7 +491,12 @@ class CacheEntry {
    * Invalidate the result represented by the given [descriptor] and propagate
    * invalidation to other results that depend on it.
    */
-  void _invalidate(ResultDescriptor descriptor) {
+  void _invalidate(ResultDescriptor descriptor, Delta delta) {
+    if (delta != null &&
+        !delta.affects(_partition.context, target, descriptor)) {
+//      print('not-invalidate $descriptor for $target');
+      return;
+    }
 //    print('invalidate $descriptor for $target');
     ResultData thisData = _resultMap.remove(descriptor);
     if (thisData == null) {
@@ -511,7 +516,7 @@ class CacheEntry {
     dependentResults.forEach((TargetedResult dependentResult) {
       CacheEntry entry = _partition.get(dependentResult.target);
       if (entry != null) {
-        entry._invalidate(dependentResult.result);
+        entry._invalidate(dependentResult.result, delta);
       }
     });
     // If empty, remove the entry altogether.
@@ -530,7 +535,7 @@ class CacheEntry {
   void _invalidateAll() {
     List<ResultDescriptor> results = _resultMap.keys.toList();
     for (ResultDescriptor result in results) {
-      _invalidate(result);
+      _invalidate(result, null);
     }
   }
 
@@ -960,6 +965,24 @@ abstract class CachePartition {
 }
 
 /**
+ * The description for a change.
+ */
+class Delta {
+  final Source source;
+
+  Delta(this.source);
+
+  /**
+   * Check whether this delta affects the result described by the given
+   * [descriptor] and [target].
+   */
+  bool affects(InternalAnalysisContext context, AnalysisTarget target,
+      ResultDescriptor descriptor) {
+    return true;
+  }
+}
+
+/**
  * [InvalidatedResult] describes an invalidated result.
  */
 class InvalidatedResult {