Strawman: check strong mode free variables against the global object.

test/mjsunit/strong/declaration-after-use.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --strong-mode --harmony_rest_parameters --harmony_arrow_functions --harmony_classes --harmony_computed-property_names
 
 // Note that it's essential for these tests that the reference is inside dead
 // code (because we already produce ReferenceErrors for run-time unresolved
 // variables and don't want to confuse those with strong mode errors). But the
 // errors should *not* be inside lazy, unexecuted functions, since lazy parsing
@@ skipping 190 matching lines @@
   function * func2() { func2; this; }
   func2();
   func2;
 
   function func4(p, ...rest) { p; rest; this; func2; }
   func4();
 
   let func5 = (p1, p2) => { p1; p2; };
   func5();
 
+  let func5b = p1 => p1;
+  func5b();
+
   function func6() {
     var1, var2a, var2b, var2c;
   }
 
   (function eval1() {
     let var7 = 0; // Declaration position will be something large.
     // But use position will be something small, however, this is not an error,
     // since the use is inside an eval scope.
     eval("var7;");
   })();
@@ skipping 25 matching lines @@
       }
       return new CInner();
     }
   }
   (new COuter()).m().n();
 
   // Making sure the check which is supposed to prevent "object literal inside
   // computed property name references the class name" is not too generic:
   class C14 { m() { let obj = { n() { C14 } }; obj.n(); } }; (new C14()).m();
 })();