cps-ir: Do not propagate assignments into try.

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.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.
 
 part of tree_ir.optimization;
 
 /**
  * Performs the following transformations on the tree:
  * - Assignment propagation
  * - If-to-conditional conversion
@@ skipping 402 matching lines @@
     });
     return node;
   }
 
   Statement visitWhileCondition(WhileCondition node) {
     // Not introduced yet
     throw "Unexpected WhileCondition in StatementRewriter";
   }
 
   Statement visitTry(Try node) {
-    Set<Label> saved = safeForInlining;
-    safeForInlining = new Set<Label>();
-    node.tryBody = visitStatement(node.tryBody);
-    safeForInlining = saved;
-    node.catchBody = visitStatement(node.catchBody);
+    inEmptyEnvironment(() {
+      Set<Label> saved = safeForInlining;
+      safeForInlining = new Set<Label>();
+      node.tryBody = visitStatement(node.tryBody);
+      safeForInlining = saved;
+      node.catchBody = visitStatement(node.catchBody);
+    });
     return node;
   }
 
   Expression visitConstant(Constant node) {
     return node;
   }
 
   Expression visitThis(This node) {
     return node;
   }
@@ skipping 231 matching lines @@
   }
 
   Expression makeCondition(Expression e, bool polarity) {
     return polarity ? e : new Not(e);
   }
 
   Statement getBranch(If node, bool polarity) {
     return polarity ? node.thenStatement : node.elseStatement;
   }
 }