Merge pull request #1696 from michaelhkay/1136-optional-param-names-i…

…n-function-signature

1136 Optional names in typed function types

specifications/grammar-40/xpath-grammar.xml

@@ -2753,12 +2753,21 @@ ErrorVal ::= "$" VarName
     </g:choice>    
     <g:string>(</g:string>
     <g:zeroOrMore separator=",">
-      <g:ref name="SequenceType"/>
+      <g:ref name="TypedFunctionParam"/>
     </g:zeroOrMore>
     <g:string>)</g:string>
     <g:string>as</g:string>
     <g:ref name="SequenceType"/>
   </g:production>
+
+  <g:production name="TypedFunctionParam" if="xpath40 xquery40  xslt40-patterns">
+    <g:optional>
+      <g:string>$</g:string>
+      <g:ref name="EQName"/>
+      <g:string>as</g:string>
+    </g:optional>
+    <g:ref name="SequenceType"/>
+  </g:production>
 
   <g:production name="MapType" if="xpath40 xquery40 xslt40-patterns">
     <g:choice>

specifications/xquery-40/src/expressions.xml

@@ -4043,6 +4043,7 @@ types</term> (such as <code>xs:integer</code>) and function types
                <prodrecap ref="FunctionType"/>
                <prodrecap ref="AnyFunctionType"/>
                <prodrecap ref="TypedFunctionType"/>
+               <prodrecap ref="TypedFunctionParam"/>
                <prodrecap id="ChoiceItemType" ref="ChoiceItemType"/>
                <prodrecap ref="MapType"/>
                <prodrecap ref="RecordType"/>
@@ -5201,6 +5202,10 @@ name.</p>
                      <term>FunctionTest</term>, <term>ArrayTest</term>,
                      <term>MapTest</term>, and <term>RecordTest</term>, with no
                   change in meaning.</change>
+                  <change issue="1136" date="2025-01-12">
+                     Parameter names may be included in a function signature; they are purely
+                     documentary.
+                  </change>
                </changes>
 
                <p>A <nt def="FunctionType">FunctionType</nt> matches selected <termref 
@@ -5216,6 +5221,7 @@ name.</p>
                   <prodrecap role="xquery" ref="Annotation"/>
                   <prodrecap id="AnyFunctionType" ref="AnyFunctionType"/>
                   <prodrecap id="TypedFunctionType" ref="TypedFunctionType"/>
+                  <prodrecap id="TypedFunctionParam" ref="TypedFunctionParam"/>
                </scrap>
 
 
@@ -5243,10 +5249,22 @@ name.</p>
                      >subtype</termref> of the <nt def="TypedFunctionType"
                   >TypedFunctionType</nt>.</p>
 
+
+               <note><p>The keywords <code>function</code> and <code>fn</code> are synonymous.</p></note>
+
+               <p>If parameter names are included in a <nt def="TypedFunctionType">TypedFunctionType</nt>,
+               they are purely documentary and have no semantic effect. In particular, they
+               play no part in deciding whether a particular function item matches the
+               function type, and they never appear as keywords in function calls. 
+               For example the construct
+               <code>function($x as node()) as xs:string</code> designates exactly the same type
+               as <code>function(node()) as xs:string</code>.</p>
 
+               <p>Any parameter names that are supplied must be distinct 
+                  <errorref spec="XQ" class="ST" code="0039"/>.</p>
 
-               <p>In consequence, a <nt def="TypedFunctionType">TypedFunctionType</nt>
-               may match certain maps and arrays, as described in <specref ref="id-map-test"/> and
+               <p diff="add" at="issue730">A <nt def="TypedFunctionType">TypedFunctionType</nt>
+               may also match certain maps and arrays, as described in <specref ref="id-map-test"/> and
                <specref ref="id-array-test"/></p>
 
 
@@ -5269,6 +5287,10 @@ name.</p>
                         because the signature of the function item <code>fn:count#1</code>
                         is a subtype of <code>function(xs:string*) as item()</code>.
                      </p>
+
+                     <note><p>The same type might also be written 
+                        <code>fn($x as xs:int, $y as xs:int) as xs:int</code>.</p></note>
+
                   </item>
                   <item role="xquery">
                      <p>