fix(frontends/lean): universe variable is treated as parameter inside section, fixes #283

src/frontends/lean/decl_cmds.cpp

@@ -26,7 +26,7 @@ Author: Leonardo de Moura
 namespace lean {
 static environment declare_universe(parser & p, environment env, name const & n, bool local) {
     if (in_context(env) || local) {
-        p.add_local_level(n, mk_param_univ(n));
+        p.add_local_level(n, mk_param_univ(n), local);
     } else {
         name const & ns = get_namespace(env);
         name full_n  = ns + n;
@@ -399,9 +399,10 @@ environment definition_cmd_core(parser & p, bool is_theorem, bool is_opaque, boo
         erase_local_binder_info(new_locals);
         value = Fun_as_is(new_locals, value, p);
         update_univ_parameters(ls_buffer, collect_univ_params(value, collect_univ_params(type)), p);
+        remove_local_vars(p, locals);
         ls = to_list(ls_buffer.begin(), ls_buffer.end());
         levels local_ls = collect_local_nonvar_levels(p, ls);
-        remove_local_vars(p, locals);
+        local_ls = remove_local_vars(p, local_ls);
         if (!locals.empty()) {
             expr ref = mk_local_ref(real_n, local_ls, locals);
             p.add_local_expr(n, ref);

src/frontends/lean/util.cpp

@@ -98,6 +98,12 @@ void remove_local_vars(parser const & p, buffer<expr> & locals) {
     locals.shrink(j);
 }
 
+levels remove_local_vars(parser const & p, levels const & ls) {
+    return filter(ls, [&](level const & l) {
+            return !is_param(l) || !p.is_local_level_variable(param_id(l));
+        });
+}
+
 list<expr> locals_to_context(expr const & e, parser const & p) {
     expr_struct_set ls;
     collect_locals(e, ls);

src/frontends/lean/util.h

@@ -32,6 +32,8 @@ void collect_locals(expr const & type, expr const & value, parser const & p, buf
 void sort_locals(expr_struct_set const & locals, parser const & p, buffer<expr> & ps);
 /** \brief Remove from \c ps local constants that are tagged as variables. */
 void remove_local_vars(parser const & p, buffer<expr> & ps);
+/** \brief Remove from \c ls any universe level that is tagged as variable in \c p */
+levels remove_local_vars(parser const & p, levels const & ls);
 list<expr> locals_to_context(expr const & e, parser const & p);
 /** \brief Create the term <tt>(as_atomic (@n.{ls} @params[0] ... @params[num_params-1]))</tt>
     When we declare \c n inside of a context, the parameters and universes are fixed.

tests/lean/run/uni_var_bug.lean

@@ -0,0 +1,15 @@
+import logic.eq
+
+section
+universe variable u
+variables {A B : Type.{u}}
+theorem foo (H : A = B) : A = B := H
+theorem bar {C D : Type} (H : C = D) : C = D :=
+foo H
+end
+
+universe variable u
+variables {A B : Type.{u}}
+theorem foo2 (H : A = B) : A = B := H
+theorem bar2 {C D : Type} (H : C = D) : C = D :=
+foo2 H

tests/lean/univ_vars.lean.expected.out

@@ -1,5 +1,5 @@
 id1 : Π (A : Type.{u}), A → A
 id2.{l_2} : Π (B : Type.{l_2}), B → B
-id3.{k} : Π (C : Type.{k}), C → C
-foo.{l} : Π (A₁ A₂ : Type.{l}), A₁ → A₂ → Prop
+id3.{l_2} : Π (C : Type.{l_2}), C → C
+foo.{l_2} : Π (A₁ A₂ : Type.{l_2}), A₁ → A₂ → Prop
 Type.{m} : Type.{succ m}