feat(frontends/lean/parser): reject explicit universe levels in variables and parameters

This modification was motivated by issue #427

src/frontends/lean/parser.cpp

@@ -1079,7 +1079,10 @@ expr parser::id_to_expr(name const & id, pos_info const & p) {
 
     // locals
     if (auto it1 = m_local_decls.find(id)) {
-        auto r = copy_with_new_pos(propagate_levels(*it1, ls), p);
+        if (ls && m_undef_id_behavior != undef_id_behavior::AssumeConstant)
+            throw parser_error("invalid use of explicit universe parameter, identifier is a variable, "
+                               "parameter or a constant bound to parameters in a section/context", p);
+        auto r = copy_with_new_pos(*it1, p);
         save_type_info(r);
         save_identifier_info(p, id);
         return r;

tests/lean/sec3.lean

@@ -0,0 +1,6 @@
+context
+  parameter A : Type
+  definition tst (a : A) := a
+  set_option pp.universes true
+  check tst.{1}
+end

tests/lean/sec3.lean.expected.out

@@ -0,0 +1 @@
+sec3.lean:5:8: error: invalid use of explicit universe parameter, identifier is a variable, parameter or a constant bound to parameters in a section/context