Remove redundant stack shuffling from hashtable implementation

core/hashtables/hashtables-docs.factor

@@ -70,7 +70,7 @@ HELP: nth-pair
 { nth-pair set-nth-pair } related-words
 
 HELP: set-nth-pair
-{ $values { "value" "the second element of the pair" } { "key" "the first element of the pair" } { "n" "an index in the sequence" } { "seq" "a sequence" } }
+{ $values { "value" "the second element of the pair" } { "key" "the first element of the pair" } { "seq" "a sequence" } { "n" "an index in the sequence" } }
 { $description "Stores a pair of values into the elements with index " { $snippet "n" } " and " { $snippet "n+1" } ", respectively." }
 { $warning "This word is in the " { $vocab-link "hashtables.private" } " vocabulary because it does not perform bounds checks." }
 { $side-effects "seq" } ;

core/hashtables/hashtables.factor

@@ -59,8 +59,7 @@ IN: hashtables
     swap 2 fixnum+fast 2dup slot -rot 1 fixnum+fast slot ;
     inline
 
-: set-nth-pair ( value key n seq -- )
-    swap
+: set-nth-pair ( value key seq n -- )
     2 fixnum+fast [ set-slot ] 2keep
     1 fixnum+fast set-slot ; inline
 
@@ -73,7 +72,7 @@ IN: hashtables
 : (set-hash) ( value key hash -- )
     2dup new-key@
     [ rot hash-count+ ] [ rot drop ] if
-    swap set-nth-pair ; inline
+    set-nth-pair ; inline
 
 : find-pair-next >r 2 fixnum+fast r> ; inline
 
@@ -133,7 +132,7 @@ M: hashtable clear-assoc ( hash -- )
 
 M: hashtable delete-at ( key hash -- )
     tuck key@ [
-        >r >r ((tombstone)) dup r> r> swap set-nth-pair
+        >r >r ((tombstone)) dup r> r> set-nth-pair
         hash-deleted+
     ] [
         3drop