Use entities in code_emitter_task

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

 // Copyright (c) 2012, 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.
 
 /// This library defines individual world impacts.
 ///
 /// We call these building blocks `uses`. Each `use` is a single impact of the
 /// world. Some example uses are:
 ///
 ///  * an invocation of a top level function
@@ skipping 311 matching lines @@
             "or boxed field."));
     return new StaticUse.internal(element, StaticUseKind.FIELD_SET);
   }
 
   /// Read of a local function [element].
   factory StaticUse.closure(LocalFunctionElement element) {
     return new StaticUse.internal(element, StaticUseKind.CLOSURE);
   }
 
   /// Unknown use of [element].
+  ///
+  /// Avoid using this, if possible: Use one of the other constructor which more
+  /// precisely capture why [element] is used.
   @deprecated
   factory StaticUse.foreignUse(Entity element) {
     return new StaticUse.internal(element, StaticUseKind.GENERAL);
   }
 
   /// Direct use of [element] as done with `--analyze-all` and `--analyze-main`.
   factory StaticUse.directUse(Entity element) {
     return new StaticUse.internal(element, StaticUseKind.DIRECT_USE);
   }
 
@@ skipping 69 matching lines @@
   }
 
   bool operator ==(other) {
     if (identical(this, other)) return true;
     if (other is! TypeUse) return false;
     return type == other.type && kind == other.kind;
   }
 
   String toString() => 'TypeUse($type,$kind)';
 }