feat(frontends/lean/builtin_cmds): allow many namespaces in the same 'using' command

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/frontends/lean/builtin_cmds.cpp

@@ -170,6 +170,7 @@ static void check_identifier(parser & p, environment const & env, name const & n
 // using [class] id (id ...) (renaming id->id id->id) (hiding id ... id)
 environment using_cmd(parser & p) {
     environment env = p.env();
+    while (true) {
         name cls = parse_class(p);
         bool decls = cls.is_anonymous() || cls == g_decls || cls == g_declarations;
         name ns    = p.check_id_next("invalid 'using' command, identifier expected");
@@ -217,6 +218,9 @@ environment using_cmd(parser & p) {
             if (!found_explicit)
                 env = add_aliases(env, ns, name(), exceptions.size(), exceptions.data());
         }
+        if (!p.curr_is_token(g_lbracket) && !p.curr_is_identifier())
+            break;
+    }
     return env;
 }
 

tests/lean/run/class1.lean

@@ -1,6 +1,5 @@
 import standard
-using num
+using num pair
-using pair
 
 definition H : inhabited (Bool × num × (num → num)) := _
 

tests/lean/run/class2.lean

@@ -1,6 +1,5 @@
 import standard
-using num
+using num pair
-using pair
 
 theorem H {A B : Type} (H1 : inhabited A) : inhabited (Bool × A × (B → num))
 := _

tests/lean/run/class3.lean

@@ -1,6 +1,5 @@
 import standard
-using num
+using num pair
-using pair
 
 section
   parameter {A : Type}

tests/lean/run/class5.lean

@@ -25,8 +25,7 @@ namespace nat
 end
 
 section
-  using algebra
+  using algebra nat
-  using nat
   variables a b c : nat
   check a * b * c
 end