Compute NativeBasicData for KernelWorldBuilder

pkg/compiler/lib/src/kernel/native_basic_data.dart

+// Copyright (c) 2017, 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.
+
+part of dart2js.kernel.world_builder;
+
+/// Computes that NativeBasicData for the libraries in [worldBuilder].
+// TODO(johnnniwinther): Move this to the AnnotationProcessor when it has been
+// committed.
+NativeBasicData computeNativeBasicData(KernelWorldBuilder worldBuilder) {
+  NativeBasicDataBuilderImpl builder = new NativeBasicDataBuilderImpl();
+  ElementEnvironment elementEnvironment = worldBuilder.elementEnvironment;
+  for (LibraryEntity library in elementEnvironment.libraries) {
+    /// TODO(johnniwinther): Reuse `JavaScriptBackend.canLibraryUseNative`
+    /// instead.
+    if (library.canonicalUri.scheme == 'dart') {
+      elementEnvironment.forEachClass(library, (ClassEntity cls) {
+        String annotationName;
+        for (ConstantExpression annotation
+            in worldBuilder._getClassMetadata(cls)) {

[Siggi Cherem (dart-lang), 2017/04/19 16:05:22]

I might be missing sometheing, but isn't this a type mismatch here? (`cls` is an
entity, but _getClassMetadata expects a `KClassEnv`)?

I expect we want to fix _getClassMetadata, right? (we want to keep KEnv* private
to this library, correct?) If so, can we make them private classes too?

[Johnni Winther, 2017/04/20 08:05:25]

_getClassMetadata expects a KClass but uses _classEnvs to compute its metadata.
Will do in a later CL.

+          ConstantValue value =
+              worldBuilder.constantEnvironment.getConstantValue(annotation);

[Siggi Cherem (dart-lang), 2017/04/19 16:05:22]

ah - this might answer part of my question from my other CL - do we need to have
a world builder in order to get a constant environment? Does that mean that we
can't really do much without a world builder from early stages of the compiler?

[Johnni Winther, 2017/04/20 08:05:25]

We need the KernelWorldBuilder from the get-go. That's why it needs to be in the
'FrontStrategy' for kernel.

+          String name = readAnnotationName(
+              cls, value, worldBuilder.commonElements.nativeAnnotationClass);
+          if (annotationName == null) {
+            annotationName = name;
+          } else if (name != null) {
+            throw new SpannableAssertionFailure(
+                cls, 'Too many name annotations.');
+          }
+        }
+        if (annotationName != null) {
+          builder.setNativeClassTagInfo(cls, annotationName);
+        }
+      });
+    }
+  }
+  return builder.close(worldBuilder.elementEnvironment);

[Siggi Cherem (dart-lang), 2017/04/19 16:05:22]

use directly the local elementEnvironment

[Johnni Winther, 2017/04/20 08:05:25]

Done.

+}