Use SummarySdkAnalysisContext if the SDK has the analysis_summary file.

pkg/analyzer/lib/src/summary/summary_sdk.dart

Index: pkg/analyzer/lib/src/summary/summary_sdk.dart
diff --git a/pkg/analyzer/lib/src/summary/summary_sdk.dart b/pkg/analyzer/lib/src/summary/summary_sdk.dart
index da2ca8eee76e335705456147e94407ae3da85282..f112297f9747578bede8b8f9b0b1c184296eb300 100644
--- a/pkg/analyzer/lib/src/summary/summary_sdk.dart
+++ b/pkg/analyzer/lib/src/summary/summary_sdk.dart
@@ -6,9 +6,115 @@ library analyzer.src.summary.summary_sdk;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/src/context/cache.dart' show CacheEntry;
+import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/resolver.dart';
+import 'package:analyzer/src/generated/source.dart' show Source, SourceKind;
+import 'package:analyzer/src/summary/format.dart';
+import 'package:analyzer/src/summary/resynthesize.dart';
+import 'package:analyzer/src/task/dart.dart'
+    show
+        LIBRARY_ELEMENT1,
+        LIBRARY_ELEMENT2,
+        LIBRARY_ELEMENT3,
+        LIBRARY_ELEMENT4,
+        LIBRARY_ELEMENT5,
+        LIBRARY_ELEMENT6,
+        LIBRARY_ELEMENT7,
+        LIBRARY_ELEMENT8,
+        READY_LIBRARY_ELEMENT2,
+        READY_LIBRARY_ELEMENT5,
+        READY_LIBRARY_ELEMENT6,
+        TYPE_PROVIDER;
+import 'package:analyzer/task/dart.dart';
+import 'package:analyzer/task/model.dart'
+    show AnalysisTarget, ResultDescriptor, TargetedResult;
+
+/**
+ * An [SdkAnalysisContext] for Dart SDK with a summary [SdkBundle].
+ */
+class SummarySdkAnalysisContext extends SdkAnalysisContext {
+  final SdkBundle bundle;
+  final SummaryTypeProvider typeProvider = new SummaryTypeProvider();
+
+  SummaryResynthesizer resynthesizer;
+
+  SummarySdkAnalysisContext(this.bundle);
+
+  @override
+  bool aboutToComputeResult(CacheEntry entry, ResultDescriptor result) {
+    if (resynthesizer == null) {

[Brian Wilkerson, 2016/01/05 18:46:18]

Is there any reason to do this lazily? It seems like we will always create a
resynthesizer, so why not do it once up front and avoid the test?

[scheglov, 2016/01/05 20:27:57]

The property "sourceFactory" is set after the context is created.
There is also a circular dependency between DartSdk.context and
PartitionManager.forSdk().
So, we need to create the context instance before setting "sourceFactory".

+      resynthesizer = new SummaryResynthesizer(this, typeProvider,
+          _getPrelinkedSummary, _getUnlinkedSummary, sourceFactory);
+      _buildCoreLibrary();
+      _buildAsyncLibrary();
+    }
+    if (result == TYPE_PROVIDER) {
+      entry.setValue(result, typeProvider, TargetedResult.EMPTY_LIST);
+      return true;
+    }
+    AnalysisTarget target = entry.target;
+    if (target is Source && target.isInSystemLibrary) {
+      if (result == LIBRARY_ELEMENT1 ||
+          result == LIBRARY_ELEMENT2 ||
+          result == LIBRARY_ELEMENT3 ||
+          result == LIBRARY_ELEMENT4 ||
+          result == LIBRARY_ELEMENT5 ||
+          result == LIBRARY_ELEMENT6 ||
+          result == LIBRARY_ELEMENT7 ||
+          result == LIBRARY_ELEMENT8 ||
+          result == LIBRARY_ELEMENT) {

[Paul Berry, 2016/01/05 19:33:43]

Is it going to be a maintenance burden to keep this chain of equality tests
updated when we modify the element model?  Maybe there should be a field in
ResultDescriptor expressing the relationship between all of the various
LIBRARY_ELEMENT*s (e.g. maybe a ".whenComplete" field that expresses what the
result will look like when it's been completely built), so we could instead say
something like:

if (result.whenComplete == LIBRARY_ELEMENT)

[scheglov, 2016/01/05 20:27:57]

Sounds interesting.

+        String uri = target.uri.toString();
+        LibraryElement libraryElement = resynthesizer.getLibraryElement(uri);
+        entry.setValue(result, libraryElement, TargetedResult.EMPTY_LIST);
+        return true;
+      } else if (result == READY_LIBRARY_ELEMENT2 ||
+          result == READY_LIBRARY_ELEMENT5 ||
+          result == READY_LIBRARY_ELEMENT6) {
+        entry.setValue(result, true, TargetedResult.EMPTY_LIST);
+        return true;
+      } else if (result == SOURCE_KIND) {
+        // TODO(scheglov) not every source is a library

[Paul Berry, 2016/01/05 19:33:43]

I think the only way this could be reached is if the code being analyzed tries
to refer to one of the SDK's part files directly, e.g.:

import "dart:core/bool.dart";

Maybe we should implement just enough logic to ensure that the correct error
messages will get generated, and then add some unit tests to verify that they
work properly.

[scheglov, 2016/01/05 20:27:57]

Yes.
For now it is just a placeholder.
Once we will start adding tests, we will provide better implementation.

+        print(target.source.uri);

[Brian Wilkerson, 2016/01/05 18:46:18]

Remove?

[scheglov, 2016/01/05 20:27:57]

Done.

+        entry.setValue(result, SourceKind.LIBRARY, TargetedResult.EMPTY_LIST);
+        return true;

[Brian Wilkerson, 2016/01/05 18:46:18]

Should this return `false` for now until we can correctly compute the kind?

[scheglov, 2016/01/05 20:27:57]

Returning `false` mean that we cannot provide this information.
We can provide it, but we do it incorrectly for now :-)
We don't want to read/scan/parse the source.

[Brian Wilkerson, 2016/01/05 20:42:51]

Could we implement it correctly by just testing whether
"sourceFactory.dartSdk.uris.contains(target.source.uri)"?

+      } else {
+        throw new UnimplementedError('$result of $target');

[Brian Wilkerson, 2016/01/05 18:46:18]

Is this for debugging? If so, perhaps comment it out (or at least add a TODO).

[scheglov, 2016/01/05 20:27:57]

Done.

+      }
+    }
+    return false;
+  }
+
+  void _buildAsyncLibrary() {
+    LibraryElement library = resynthesizer.getLibraryElement('dart:async');
+    typeProvider.initializeAsync(library);
+  }
+
+  void _buildCoreLibrary() {
+    LibraryElement library = resynthesizer.getLibraryElement('dart:core');
+    typeProvider.initializeCore(library);
+  }
+
+  PrelinkedLibrary _getPrelinkedSummary(String uri) {
+    for (int i = 0; i < bundle.prelinkedLibraryUris.length; i++) {
+      if (bundle.prelinkedLibraryUris[i] == uri) {
+        return bundle.prelinkedLibraries[i];
+      }
+    }
+    throw new StateError('Unable to find prelinked summary for $uri');

[Paul Berry, 2016/01/05 19:33:43]

Is there a danger of this code getting triggered if the user tries to import an
SDK library that doesn't exist, e.g.:

import "dart:macaroons";

and causing a crash rather than generating the appropriate error?

[scheglov, 2016/01/05 20:27:57]

No, if a URI is not resolved to an existing Source, we don't even ask for its
elements.

There is not much what we could do here - we're asked for the summary, and we
need to return something. Returning `null` seems worse than providing
information in exception.

+  }
+
+  UnlinkedUnit _getUnlinkedSummary(String uri) {
+    for (int i = 0; i < bundle.unlinkedUnitUris.length; i++) {
+      if (bundle.unlinkedUnitUris[i] == uri) {
+        return bundle.unlinkedUnits[i];
+      }
+    }
+    throw new StateError('Unable to find unlinked summary for $uri');
+  }
+}
 
 /**
  * Implementation of [TypeProvider] which can be initialized separately with