[m-rev.] for review: correct type of java list.cons

[Peter Wang]

For review by Ian.

Branches: main, 10.04

doc/reference_manual.texi:
library/list.m:
        Correct the type of the Java method `list.cons' so that the
        head element may have a subtype of the list element type. 

        Add a comment about how to use `list.empty_list'.

diff --git a/doc/reference_manual.texi b/doc/reference_manual.texi
index 6ad36ef..0c48bd6 100644
--- a/doc/reference_manual.texi
+++ b/doc/reference_manual.texi
@@ -7110,7 +7110,8 @@ boolean   list.is_empty(List_1<E> list)     // test if a list is empty
 E         list.det_head(List_1<E> list)     // get the head of a list
 List_1<E> list.det_tail(List_1<E> list)     // get the tail of a list
 List_1<E> list.empty_list()                 // create an empty list
-List_1<E> list.cons(E head, List_1<E> tail) // construct a list with
+<E, F extends E> List_1<E> list.cons(F head, List_1<E> tail)
+                                            // construct a list with
                                             //  the given head and tail
 @end example
 
diff --git a/library/list.m b/library/list.m
index 99433e5..a112c37 100644
--- a/library/list.m
+++ b/library/list.m
@@ -2867,14 +2867,18 @@ list_to_doc_2([X | Xs]) = Doc :-
 ** the interfaces would expect type_info arguments.
 */
 
+/*
+** If you need to specify the type parameter, you must use the qualified
+** method name, e.g. list.<Integer>empty_list()
+*/
 public static <E>
 List_1<E> empty_list()
 {
     return new List_1.F_nil_0<E>();
 }
 
-public static <E>
-List_1<E> cons(E head, List_1<E> tail)
+public static <E, F extends E>
+List_1<E> cons(F head, List_1<E> tail)
 {
     return new List_1.F_cons_2<E>(head, tail);
 }

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