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

… to positive zero

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

Closes #316

spec.html

@@ -25291,10 +25291,12 @@ <h1>TimeClip (_time_)</h1>
         <emu-alg>
           1. If _time_ is not finite, return *NaN*.
           1. If abs(_time_) &gt; 8.64 &times; 10<sup>15</sup>, return *NaN*.
-          1. Return ToInteger(_time_) + (*+0*). (Adding a positive zero converts *-0* to *+0*.)
+          1. Let _clippedTime_ be ToInteger(_time_).
+          1. If _clippedTime_ is -0, let _clippedTime_ be +0.
+          1. Return _clippedTime_.
         </emu-alg>
         <emu-note>
-          <p>The point of step 3 is that an implementation is permitted a choice of internal representations of time values, for example as a 64-bit signed integer or as a 64-bit floating-point value. Depending on the implementation, this internal representation may or may not distinguish *-0* and *+0*.</p>
+          <p>The point of step 4 is that an implementation is permitted a choice of internal representations of time values, for example as a 64-bit signed integer or as a 64-bit floating-point value. Depending on the implementation, this internal representation may or may not distinguish *-0* and *+0*.</p>
         </emu-note>
       </emu-clause>
 
@@ -29388,7 +29390,7 @@ <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
@@ -29829,7 +29831,7 @@ <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. If _n_ is -0, let _k_ be +0; else let _k_ be _n_.
           1. Else _n_ &lt; 0,
             1. Let _k_ be _len_ + _n_.
             1. If _k_ &lt; 0, let _k_ be 0.
@@ -29899,7 +29901,8 @@ <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. If _n_ is -0, let _k_ be +0; else let _k_ be min(_n_, _len_ - 1).
           1. Else _n_ &lt; 0,
             1. Let _k_ be _len_ + _n_.
           1. Repeat, while _k_ &ge; 0
@@ -30993,7 +30996,7 @@ <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>