fix(frontends/lean/elaborator): fix bugs and adjust tests

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

src/frontends/lean/frontend_elaborator.cpp

@@ -197,7 +197,8 @@ class frontend_elaborator::imp {
         /**
            \brief Create a metavariable for representing the choice.
         */
-        expr mk_overload_mvar(buffer<expr> const & f_choices, context const & ctx, expr const & src) {
+        expr mk_overload_mvar(buffer<expr> & f_choices, context const & ctx, expr const & src) {
+            std::reverse(f_choices.begin(), f_choices.end());
             expr mvar = m_ref.m_menv.mk_metavar(ctx);
             m_ref.m_ucs.push_back(mk_choice_constraint(ctx, mvar, f_choices.size(), f_choices.data(),
                                                        mk_overload_justification(ctx, src)));

tests/lean/arith1.lean.expected.out

@@ -14,6 +14,6 @@ n + x + m
   Set: lean::pp::coercion
 (nat_to_int n) + x + (nat_to_int m) + (nat_to_int 10)
 x + (nat_to_int n) + (nat_to_int m) + (nat_to_int 10)
-(nat_to_int (n + m + 10)) + x
+(nat_to_int n) + (nat_to_int m) + (nat_to_int 10) + x
   Set: lean::pp::notation
-Int::add (nat_to_int (Nat::add (Nat::add n m) 10)) x
+Int::add (Int::add (Int::add (nat_to_int n) (nat_to_int m)) (nat_to_int 10)) x

tests/lean/cast3.lean.expected.out

@@ -6,7 +6,7 @@
   Assumed: B'
   Assumed: x
 x
-⊤
+x = x
   Assumed: b
   Defined: f
   Assumed: H

tests/lean/overload2.lean.expected.out

@@ -23,10 +23,4 @@ f a b
 f (r2t b) (t2r a)
   Assumed: g
 f a b
-Error (line: 19, pos: 10) ambiguous overloads
-Candidates:
-    g : R → T → R
-    f : T → R → T
-Arguments:
-    b : R
-    a : T
+f (r2t b) (t2r a)