Strict mode eval declares its locals in its own environment.

src/scopes.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 193 matching lines @@
   }
 
   // ---------------------------------------------------------------------------
   // Predicates.
 
   // Specific scope types.
   bool is_eval_scope() const { return type_ == EVAL_SCOPE; }
   bool is_function_scope() const { return type_ == FUNCTION_SCOPE; }
   bool is_global_scope() const { return type_ == GLOBAL_SCOPE; }
   bool is_strict_mode() const { return strict_mode_; }
+  bool is_strict_mode_eval_scope() const {
+    return is_eval_scope() && is_strict_mode();
+  }
 
   // Information about which scopes calls eval.
   bool calls_eval() const { return scope_calls_eval_; }
   bool outer_scope_calls_eval() const { return outer_scope_calls_eval_; }
 
   // Is this scope inside a with statement.
   bool inside_with() const { return scope_inside_with_; }
   // Does this scope contain a with statement.
   bool contains_with() const { return scope_contains_with_; }
 
@@ skipping 253 matching lines @@
   int nesting_level_;
   // Nesting level of outermost scope that is contained in a with statement,
   // or kNotInsideWith if there are no with's around the current scope.
   int inside_with_level_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_