Unbreak singleton list-like notation (-compat 8.4)

With this commit, it is possible to write notations so that singleton
lists are usable in both 8.4 and 8.5pl1 -compat.  Longer lists await the
ability to remove notations from the parser.

1 files changed, 34 insertions, 0 deletions

diff --git a/test-suite/bugs/opened/4803.v b/test-suite/bugs/opened/4803.v
new file mode 100644
index 000000000..3ca5c095f
--- /dev/null
+++ b/test-suite/bugs/opened/4803.v
@@ -0,0 +1,34 @@
+(* -*- coq-prog-args: ("-emacs" "-compat" "8.4") -*- *)
+(*Suppose a user wants to declare a new list-like notation with support for singletons in both 8.4 and 8.5.  If they use*)
+Require Import Coq.Lists.List.
+Require Import Coq.Vectors.Vector.
+Import ListNotations.
+Import VectorNotations.
+Set Implicit Arguments.
+Inductive mylist T := mynil | mycons (_ : T) (_ : mylist T).
+Arguments mynil {_}, _.
+
+Delimit Scope mylist_scope with mylist.
+Bind Scope mylist_scope with mylist.
+Delimit Scope vector_scope with vector.
+
+Notation " [ ] " := mynil (format "[ ]") : mylist_scope.
+Notation " [ x ] " := (mycons x mynil) : mylist_scope.
+Notation " [ x ; .. ; y ] " := (mycons x .. (mycons y mynil) ..) : mylist_scope.
+
+(** All of these should work fine in -compat 8.4 mode, just as they do in Coq 8.4.  There needs to be a way to specify notations above so that all of these [Check]s go through in both 8.4 and 8.5 *)
+Check [ ]%mylist : mylist _.
+Check [ ]%list : list _.
+Check []%vector : Vector.t _ _.
+Check [ _ ]%mylist : mylist _.
+Check [ _ ]%list : list _.
+Check [ _ ]%vector : Vector.t _ _.
+Check [ _ ; _ ]%list : list _.
+Check [ _ ; _ ]%vector : Vector.t _ _.
+Fail Check [ _ ; _ ]%mylist : mylist _. (* ideally, this should work, but that requires removing notations from the parser; it should be added to Compat/Coq84.v *)
+Check [ _ ; _ ; _ ]%list : list _.
+Check [ _ ; _ ; _ ]%vector : Vector.t _ _.
+Fail Check [ _ ; _ ; _ ]%mylist : mylist _. (* ideally, this should work, but that requires removing notations from the parser *)
+Check [ _ ; _ ; _ ; _ ]%list : list _.
+Check [ _ ; _ ; _ ; _ ]%vector : Vector.t _ _.
+Fail Check [ _ ; _ ; _ ; _ ]%mylist : mylist _. (* ideally, this should work, but that requires removing notations from the parser *)