I have modified the grammar for idts (sequences of identifiers with optional
type annotations). idts are generally used as in abstractions, be it
lambda-abstraction or quantifiers. It now has roughly the form

idts = pttrn*
pttrn = idt

where pttrn is a new nonterminal (type) not used anywhere else.
This means that the Pure syntax for idts is in fact unchanged.
The point is that the new nontermianl pttrn allows later extensions of this
syntax. (See, for example, HOL/Prod.thy).

The name idts is not quite accurate any longer and may become downright
confusing once pttrn has been extended. Something should be done about this,
in particular wrt to the manual.

--- a/src/Pure/Syntax/mixfix.ML	Wed Apr 19 19:15:29 1995 +0200
+++ b/src/Pure/Syntax/mixfix.ML	Sat Apr 22 12:21:41 1995 +0200
@@ -140,7 +140,7 @@
 val pure_types =
   map (fn t => (t, 0, NoSyn))
     (terminals @ [logic, "type", "types", "sort", "classes", args,
-      "idt", "idts", "aprop", "asms", any, sprop]);
+      "pttrn", "idt", "idts", "aprop", "asms", any, sprop]);
 
 val pure_syntax =
  [("_lambda",   "[idts, 'a] => logic",            Mixfix ("(3%_./ _)", [], 0)),
@@ -150,8 +150,9 @@
   ("",          "id => idt",                      Delimfix "_"),
   ("_idtyp",    "[id, type] => idt",              Mixfix ("_::_", [], 0)),
   ("",          "idt => idt",                     Delimfix "'(_')"),
-  ("",          "idt => idts",                    Delimfix "_"),
-  ("_idts",     "[idt, idts] => idts",            Mixfix ("_/ _", [1, 0], 0)),
+  ("",          "idt => pttrn",                   Delimfix "_"),
+  ("",          "pttrn => idts",                  Delimfix "_"),
+  ("_idts",     "[pttrn, idts] => idts",          Mixfix ("_/ _", [1, 0], 0)),
   ("",          "id => aprop",                    Delimfix "_"),
   ("",          "var => aprop",                   Delimfix "_"),
   ("_aprop",    "aprop => prop",                  Delimfix "PROP _"),