Add +0 to Array.prototype.indexOf to convert negative zero to positiv…

…e zero

Fixes https://bugs.ecmascript.org/show_bug.cgi?id=4545

spec.html

@@ -29368,7 +29368,7 @@ <h1>Array.from ( _items_ [ , _mapfn_ [ , _thisArg_ ] ] )</h1>
               1. Let _defineStatus_ be CreateDataPropertyOrThrow(_A_, _Pk_, _mappedValue_).
               1. If _defineStatus_ is an abrupt completion, return ? IteratorClose(_iterator_, _defineStatus_).
               1. Increase _k_ by 1.
-          1. Note: _items_ is not an Iterable so assume it is an array-like object.
+          1. NOTE: _items_ is not an Iterable so assume it is an array-like object.
           1. Let _arrayLike_ be ! ToObject(_items_).
           1. Let _len_ be ? ToLength(? Get(_arrayLike_, `"length"`)).
           1. If IsConstructor(_C_) is *true*, then
@@ -29809,7 +29809,8 @@ <h1>Array.prototype.indexOf ( _searchElement_ [ , _fromIndex_ ] )</h1>
           1. Let _n_ be ? ToInteger(_fromIndex_). (If _fromIndex_ is *undefined*, this step produces the value 0.)
           1. If _n_ &ge; _len_, return -1.
           1. If _n_ &ge; 0, then
-            1. Let _k_ be _n_.
+            1. Let _k_ be _n_ + (*+0*).
+            1. NOTE: Adding a positive zero converts *-0* to *+0*.
           1. Else _n_ &lt; 0,
             1. Let _k_ be _len_ + _n_.
             1. If _k_ &lt; 0, let _k_ be 0.
@@ -29879,7 +29880,9 @@ <h1>Array.prototype.lastIndexOf ( _searchElement_ [ , _fromIndex_ ] )</h1>
           1. Let _len_ be ? ToLength(? Get(_O_, `"length"`)).
           1. If _len_ is 0, return -1.
           1. If argument _fromIndex_ was passed, let _n_ be ? ToInteger(_fromIndex_); else let _n_ be _len_-1.
-          1. If _n_ &ge; 0, let _k_ be min(_n_, _len_ - 1).
+          1. If _n_ &ge; 0, then
+            1. Let _k_ be min(_n_, _len_ - 1).
+            1. NOTE: Applying the mathematical function min(&hellip;) converts *-0* to *+0*.
           1. Else _n_ &lt; 0,
             1. Let _k_ be _len_ + _n_.
           1. Repeat, while _k_ &ge; 0
@@ -30977,7 +30980,7 @@ <h1>Runtime Semantics: IterableToArrayLike( _items_ )</h1>
                   1. Let _nextValue_ be ? IteratorValue(_next_).
                   1. Append _nextValue_ to the end of the List _values_.
               1. Return CreateArrayFromList(_values_).
-            1. Note: _items_ is not an Iterable so assume it is already an array-like object.
+            1. NOTE: _items_ is not an Iterable so assume it is already an array-like object.
             1. Return ! ToObject(_items_).
           </emu-alg>
         </emu-clause>