Merge branch 'ci/msammler/length' into 'master'

Another try at removing strings.length

See merge request !144

tests/length.ref

+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]
+length
+     : list ?A → nat
+where
+?A : [ |- Type]

tests/length.v

+From stdpp Require prelude strings list.
+
+(** Check that we always get the [length] function on lists, not on strings. *)
+Module test1.
+  Import stdpp.base.
+  Check length.
+  Import stdpp.strings.
+  Check length.
+  Import stdpp.base.
+  Check length.
+End test1.
+
+Module test2.
+  Import stdpp.prelude.
+  Check length.
+  Import stdpp.strings.
+  Check length.
+  Import stdpp.prelude.
+  Check length.
+End test2.
+
+Module test3.
+  Import stdpp.strings.
+  Check length.
+  Import stdpp.prelude.
+  Check length.
+End test3.
+
+Module test4.
+  Import stdpp.list.
+  Check length.
+  Import stdpp.strings.
+  Check length.
+  Import stdpp.list.
+  Check length.
+End test4.

theories/base.v

@@ -9,6 +9,13 @@ Set Default Proof Using "Type".
 Export ListNotations.
 From Coq.Program Require Export Basics Syntax.
 
+(** This notation is necessary to prevent [length] from being printed
+as [strings.length] if strings.v is imported and later base.v. See
+also strings.v and
+https://gitlab.mpi-sws.org/iris/stdpp/-/merge_requests/144 and
+https://gitlab.mpi-sws.org/iris/stdpp/-/merge_requests/129. *)
+Notation length := Datatypes.length.
+
 (** * Enable implicit generalization. *)
 (** This option enables implicit generalization in arguments of the form
    [`{...}] (i.e., anonymous arguments).  Unfortunately, it also enables