Reland of Ship ES2015 sloppy-mode function hoisting, let, class

test/mjsunit/regress/regress-91120.js

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-// We intend that the function declaration for g inside catch is hoisted to
-// function f's scope.  Invoke it before try/catch, in the try block, in the
-// catch block, after try/catch, and outside f, and verify that it has
-// access to the proper binding of x.
+// With ES2015 function hoisting semantics, functions are only "hoisted" out
+// of blocks by writing their values into var-scoped declarations. Therefore,
+// they access the catch binding when it syntactically appears so.
+// This is a potentially breaking change vs the old semantics, which would
+// return 'function' from g() everywhere.
+
 var x = 'global';
 
 function f() {
   var x = 'function';
-  assertEquals('function', g());
+  assertEquals(undefined, g);
   try {
-    assertEquals('function', g());
+    assertEquals(undefined, g);
     throw 'catch';
   } catch (x) {
     function g() { return x; }
-    assertEquals('function', g());
+    assertEquals('catch', g());
   }
-  assertEquals('function', g());
+  assertEquals('catch', g());
   return g;
 }
 
-assertEquals('function', f()());
+assertEquals('catch', f()());