From 30d5f675c84e0c8911c70acf689f2aa49d7d11b4 Mon Sep 17 00:00:00 2001
From: Michael Kay <mike@saxonica.com>
Date: Mon, 13 Jan 2025 00:06:07 +0000
Subject: [PATCH] Add optional names to typed function types

---
 specifications/grammar-40/xpath-grammar.xml  | 11 +++++++++-
 specifications/xquery-40/src/expressions.xml | 22 +++++++++++++++++---
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/specifications/grammar-40/xpath-grammar.xml b/specifications/grammar-40/xpath-grammar.xml
index a44c2aa95..e88501e8c 100644
--- a/specifications/grammar-40/xpath-grammar.xml
+++ b/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>
diff --git a/specifications/xquery-40/src/expressions.xml b/specifications/xquery-40/src/expressions.xml
index dd0bfe35e..f5b2f84d8 100644
--- a/specifications/xquery-40/src/expressions.xml
+++ b/specifications/xquery-40/src/expressions.xml
@@ -5182,6 +5182,10 @@ 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>
 
                <scrap>
@@ -5189,6 +5193,7 @@ name.</p>
                   <prodrecap id="FunctionType" ref="FunctionType"/>
                   <prodrecap id="AnyFunctionType" ref="AnyFunctionType"/>
                   <prodrecap id="TypedFunctionType" ref="TypedFunctionType"/>
+                  <prodrecap id="TypedFunctionParam" ref="TypedFunctionParam"/>
                </scrap>
 
 
@@ -5210,9 +5215,19 @@ name.</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 diff="add" at="issue730">In addition, 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>
 
               
@@ -5239,7 +5254,8 @@ name.</p>
                            def="dt-function-item"
                            >function item</termref> with the function signature <code>function(xs:int, xs:int) as xs:int</code>.
                      </p>
-                     <note><p>This can also be written <code>fn(xs:int, xs:int) as xs:int</code>.</p></note>
+                     <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>