Emit program and dependency information as relations in a Prolog database.

sdk/lib/_internal/compiler/implementation/world.dart

Index: sdk/lib/_internal/compiler/implementation/world.dart
diff --git a/sdk/lib/_internal/compiler/implementation/world.dart b/sdk/lib/_internal/compiler/implementation/world.dart
index ae56485644495ad46bb80e07ff225dc56c4fa746..cc8c468ef35ecea48464075ff7bd012f2a238ec9 100644
--- a/sdk/lib/_internal/compiler/implementation/world.dart
+++ b/sdk/lib/_internal/compiler/implementation/world.dart
@@ -13,10 +13,12 @@ class World {
   final Map<ClassElement, Set<MixinApplicationElement>> mixinUses =
       new Map<ClassElement, Set<MixinApplicationElement>>();
 
+  // TODO(karlklose): remove, this is a subset of the information in
+  // [ClassElement].[allSupertypes].
   final Map<ClassElement, Set<ClassElement>> _typesImplementedBySubclasses =
       new Map<ClassElement, Set<ClassElement>>();
 
-  // We keep track of subtype and subclass relationships in four
+  // We keep track of subtype and subclass relationships in three
   // distinct sets to make class hierarchy analysis faster.
   final Map<ClassElement, Set<ClassElement>> _subclasses =
       new Map<ClassElement, Set<ClassElement>>();