tree-ir: Treat getInterceptor and identical as effectively constant.

pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart

 // Copyright (c) 2014, 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.
 
 library tree_ir_nodes;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, GenericType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
@@ skipping 155 matching lines @@
  * A call to a static function or getter/setter to a static field.
  *
  * In contrast to the CPS-based IR, the arguments can be arbitrary expressions.
  */
 class InvokeStatic extends Expression implements Invoke {
   final Entity target;
   final List<Expression> arguments;
   final Selector selector;
   final SourceInformation sourceInformation;
 
+  /// True if the [target] is known not to diverge or read or write any
+  /// mutable state.
+  ///
+  /// This is set for calls to `getInterceptor` and `identical` to indicate
+  /// that they can be safely be moved across an impure expression
+  /// (assuming the [arguments] are not affected by the impure expression).
+  bool isEffectivelyConstant = false;
+
   InvokeStatic(this.target, this.selector, this.arguments,
                {this.sourceInformation});
 
   accept(ExpressionVisitor visitor) => visitor.visitInvokeStatic(this);
   accept1(ExpressionVisitor1 visitor, arg) {
     return visitor.visitInvokeStatic(this, arg);
   }
 }
 
 /**
@@ skipping 1146 matching lines @@
   visitReadTypeVariable(ReadTypeVariable node) {
     node.target = visitExpression(node.target);
     return node;
   }
 
   visitTypeExpression(TypeExpression node) {
     _replaceExpressions(node.arguments);
     return node;
   }
 }