Non-format-changing kernel offset changes

pkg/kernel/lib/analyzer/loader.dart

Index: pkg/kernel/lib/analyzer/loader.dart
diff --git a/pkg/kernel/lib/analyzer/loader.dart b/pkg/kernel/lib/analyzer/loader.dart
index 43a1b3dd41f31055c6a0e81bafb19d4ae56108b9..4acb751982ef55e886ccf2ff2028b90f08210f21 100644
--- a/pkg/kernel/lib/analyzer/loader.dart
+++ b/pkg/kernel/lib/analyzer/loader.dart
@@ -268,7 +268,7 @@ class DartLoader implements ReferenceLevelLoader {
     _classes[element] = classNode = new ast.Class(
         name: element.name,
         isAbstract: element.isAbstract,
-        fileUri: '${element.source.uri}');
+        fileUri: '${element.source.uri}')..fileOffset = element.nameOffset;
     classNode.level = ast.ClassLevel.Temporary;
     var library = getLibraryReference(element.library);
     library.addClass(classNode);
@@ -317,7 +317,8 @@ class DartLoader implements ReferenceLevelLoader {
             areDistinctUnboundTypeVariables(supertype, mixinType)) {
           // Use a shared mixin application class for this library.
           var mixinClass = getSharedMixinApplicationClass(
-              scope.currentLibrary, supertype.classNode, mixinType.classNode);
+              scope.currentLibrary, supertype.classNode, mixinType.classNode)
+            ..fileOffset = element.nameOffset;

[asgerf, 2017/01/04 14:20:01]

What is the class offset used for?

Is it okay that the offset on the shared mixin class is just that of one of its
uses?

[jensj, 2017/01/05 09:07:55]

In general class offsets is used by Observatory to show the right lines from the
source file, when viewing info about a class. At the same time though, if I
remember correctly, it has to be a real offset (i.e. >= 0) or stuff will crash
(at least in some instances).

For dart files, object.cc's TokenPosition Class::ComputeEndTokenPos() seems to
return the position of the first use/creation/whatnot of the mixin class, and
then special case it (if (is_synthesized_class() || IsMixinApplication() ||
IsTopLevel())) to just show the first line...

I don't think we can really do that, unless we extend the class object (both on
dart and c++ side) to include the end token position, in which case we can set
it "correctly" here and get the same behavior for dill files as for dart files.
For now I'll change it to only set the offset, if it's not already set, that way
at least the first line shown will be the same line for dart and dill.

[asgerf, 2017/01/05 11:37:41]

Thanks for the clarification. Looks good to me then.

           supertype = new ast.Supertype(
               mixinClass,
               supertype.typeArguments.length > mixinType.typeArguments.length
@@ -333,7 +334,7 @@ class DartLoader implements ReferenceLevelLoader {
               typeParameters: freshParameters.freshTypeParameters,
               supertype: freshParameters.substituteSuper(supertype),
               mixedInType: freshParameters.substituteSuper(mixinType),
-              fileUri: classNode.fileUri);
+              fileUri: classNode.fileUri)..fileOffset = element.nameOffset;
           mixinClass.level = ast.ClassLevel.Type;
           supertype = new ast.Supertype(mixinClass,
               classNode.typeParameters.map(makeTypeParameterType).toList());
@@ -446,12 +447,14 @@ class DartLoader implements ReferenceLevelLoader {
               isStatic: true,
               isExternal: constructor.isExternal,
               isConst: constructor.isConst,
-              fileUri: '${element.source.uri}');
+              fileUri: '${element.source.uri}')
+            ..fileOffset = element.nameOffset;
         }
         return new ast.Constructor(scope.buildFunctionInterface(constructor),
             name: _nameOfMember(element),
             isConst: constructor.isConst,
-            isExternal: constructor.isExternal);
+            isExternal: constructor.isExternal)
+          ..fileOffset = element.nameOffset;
 
       case ElementKind.FIELD:
       case ElementKind.TOP_LEVEL_VARIABLE:
@@ -480,7 +483,7 @@ class DartLoader implements ReferenceLevelLoader {
             isAbstract: executable.isAbstract,
             isStatic: executable.isStatic,
             isExternal: executable.isExternal,
-            fileUri: '${element.source.uri}');
+            fileUri: '${element.source.uri}')..fileOffset = element.nameOffset;
 
       default:
         throw 'Unexpected member kind: $element';