Add ConstantUse to WorldImpact

pkg/compiler/lib/src/universe/use.dart

Index: pkg/compiler/lib/src/universe/use.dart
diff --git a/pkg/compiler/lib/src/universe/use.dart b/pkg/compiler/lib/src/universe/use.dart
index 9f5482be1b6ecba16d83e0cd4a924789fe4e669a..418d2439065ed28ab3547459b2feccd91f45821d 100644
--- a/pkg/compiler/lib/src/universe/use.dart
+++ b/pkg/compiler/lib/src/universe/use.dart
@@ -18,6 +18,7 @@ library dart2js.universe.use;
 
 import '../closure.dart' show BoxFieldElement;
 import '../common.dart';
+import '../constants/values.dart';
 import '../elements/types.dart';
 import '../elements/elements.dart' show ConstructorBodyElement, Element;
 import '../elements/entities.dart';
@@ -423,3 +424,53 @@ class TypeUse {
 
   String toString() => 'TypeUse($type,$kind)';
 }
+
+enum ConstantUseKind {
+  // A constant that is directly accessible in code.
+  DIRECT,
+  // A constant that is only accessible through other constants.
+  INDIRECT,
+}
+
+/// Use of a [ConstantValue].
+class ConstantUse {
+  final ConstantValue value;
+  final ConstantUseKind kind;
+  final int hashCode;
+
+  ConstantUse._(this.value, this.kind)
+      : this.hashCode = Hashing.objectHash(value, kind.hashCode);
+
+  /// Constant used as the initial value of a field.
+  ConstantUse.init(ConstantValue value) : this._(value, ConstantUseKind.DIRECT);
+
+  /// Type constant used for registration of custom elements.
+  ConstantUse.customElements(TypeConstantValue value)
+      : this._(value, ConstantUseKind.DIRECT);
+
+  /// Constant used through a lookup map.
+  ConstantUse.lookupMap(ConstantValue value)
+      : this._(value, ConstantUseKind.INDIRECT);
+
+  /// Constant used through mirrors.
+  // TODO(johnniwinther): Maybe if this is `DIRECT` and we can avoid the
+  // extra calls to `addCompileTimeConstantForEmission`.
+  ConstantUse.mirrors(ConstantValue value)
+      : this._(value, ConstantUseKind.INDIRECT);
+
+  /// Constant used for accessing type variables through mirrors.
+  ConstantUse.typeVariableMirror(ConstantValue value)
+      : this._(value, ConstantUseKind.DIRECT);
+
+  /// Constant literal used on code.
+  ConstantUse.literal(ConstantValue value)
+      : this._(value, ConstantUseKind.DIRECT);
+
+  bool operator ==(other) {
+    if (identical(this, other)) return true;
+    if (other is! ConstantUse) return false;
+    return value == other.value;
+  }
+
+  String toString() => 'ConstantUse(${value.toStructuredText()},$kind)';
+}