Editorial: Make IsLessThan's _LeftFirst_ param required (#2378)

spec.html

@@ -5241,8 +5241,8 @@ <h1>SameValueNonNumeric ( _x_, _y_ )</h1>
     </emu-clause>
 
     <emu-clause id="sec-islessthan" aoid="IsLessThan" oldids="sec-abstract-relational-comparison">
-      <h1>IsLessThan ( _x_, _y_ [ , _LeftFirst_ ] )</h1>
-      <p>The abstract operation IsLessThan takes arguments _x_ (an ECMAScript language value) and _y_ (an ECMAScript language value), and optional argument _LeftFirst_ (a Boolean). It provides the semantics for the comparison _x_ &lt; _y_, returning *true*, *false*, or *undefined* (which indicates that at least one operand is *NaN*). The _LeftFirst_ flag is used to control the order in which operations with potentially visible side-effects are performed upon _x_ and _y_. It is necessary because ECMAScript specifies left to right evaluation of expressions. The default value of _LeftFirst_ is *true* and indicates that the _x_ parameter corresponds to an expression that occurs to the left of the _y_ parameter's corresponding expression. If _LeftFirst_ is *false*, the reverse is the case and operations must be performed upon _y_ before _x_. It performs the following steps when called:</p>
+      <h1>IsLessThan ( _x_, _y_, _LeftFirst_ )</h1>
+      <p>The abstract operation IsLessThan takes arguments _x_ (an ECMAScript language value), _y_ (an ECMAScript language value), and _LeftFirst_ (a Boolean). It provides the semantics for the comparison _x_ &lt; _y_, returning *true*, *false*, or *undefined* (which indicates that at least one operand is *NaN*). The _LeftFirst_ flag is used to control the order in which operations with potentially visible side-effects are performed upon _x_ and _y_. It is necessary because ECMAScript specifies left to right evaluation of expressions. If _LeftFirst_ is *true*, the _x_ parameter corresponds to an expression that occurs to the left of the _y_ parameter's corresponding expression. If _LeftFirst_ is *false*, the reverse is the case and operations must be performed upon _y_ before _x_. It performs the following steps when called:</p>
       <emu-alg>
         1. If the _LeftFirst_ flag is *true*, then
           1. Let _px_ be ? ToPrimitive(_x_, ~number~).
@@ -17184,7 +17184,7 @@ <h1>Runtime Semantics: Evaluation</h1>
         1. Let _lval_ be ? GetValue(_lref_).
         1. Let _rref_ be the result of evaluating |ShiftExpression|.
         1. Let _rval_ be ? GetValue(_rref_).
-        1. Let _r_ be ? IsLessThan(_lval_, _rval_).
+        1. Let _r_ be ? IsLessThan(_lval_, _rval_, *true*).
         1. If _r_ is *undefined*, return *false*. Otherwise, return _r_.
       </emu-alg>
       <emu-grammar>RelationalExpression : RelationalExpression `&gt;` ShiftExpression</emu-grammar>
@@ -17211,7 +17211,7 @@ <h1>Runtime Semantics: Evaluation</h1>
         1. Let _lval_ be ? GetValue(_lref_).
         1. Let _rref_ be the result of evaluating |ShiftExpression|.
         1. Let _rval_ be ? GetValue(_rref_).
-        1. Let _r_ be ? IsLessThan(_lval_, _rval_).
+        1. Let _r_ be ? IsLessThan(_lval_, _rval_, *true*).
         1. If _r_ is *true* or *undefined*, return *false*. Otherwise, return *true*.
       </emu-alg>
       <emu-grammar>RelationalExpression : RelationalExpression `instanceof` ShiftExpression</emu-grammar>
@@ -33424,9 +33424,9 @@ <h1>SortCompare ( _x_, _y_ )</h1>
               1. Return _v_.
             1. [id="step-sortcompare-tostring-x"] Let _xString_ be ? ToString(_x_).
             1. [id="step-sortcompare-tostring-y"] Let _yString_ be ? ToString(_y_).
-            1. Let _xSmaller_ be IsLessThan(_xString_, _yString_).
+            1. Let _xSmaller_ be IsLessThan(_xString_, _yString_, *true*).
             1. If _xSmaller_ is *true*, return *-1*<sub>𝔽</sub>.
-            1. Let _ySmaller_ be IsLessThan(_yString_, _xString_).
+            1. Let _ySmaller_ be IsLessThan(_yString_, _xString_, *true*).
             1. If _ySmaller_ is *true*, return *1*<sub>𝔽</sub>.
             1. Return *+0*<sub>𝔽</sub>.
           </emu-alg>