feat(frontends/lean/decl_cmds): remove useless name from 'example' commad

src/frontends/lean/decl_cmds.cpp

@@ -317,7 +317,11 @@ static environment definition_cmd_core(parser & p, def_cmd_kind kind, bool is_op
     lean_assert(!(is_private && is_protected));
     auto n_pos = p.pos();
     unsigned start_line = n_pos.first;
-    name n     = p.check_id_next("invalid declaration, identifier expected");
+    name n;
+    if (kind == Example)
+        n = p.mk_fresh_name();
+    else
+        n = p.check_id_next("invalid declaration, identifier expected");
     decl_modifiers modifiers;
     name real_n; // real name for this declaration
     buffer<name> ls_buffer;

tests/lean/run/enum.lean

@@ -10,7 +10,7 @@ namespace Three
   theorem disj (a : Three) : a = zero ∨ a = one ∨ a = two :=
   rec (or.inl rfl) (or.inr (or.inl rfl)) (or.inr (or.inr rfl)) a
 
-  example ex1 (a : Three) : a ≠ zero → a ≠ one → a = two :=
+  example (a : Three) : a ≠ zero → a ≠ one → a = two :=
   rec (λ h₁ h₂, absurd rfl h₁) (λ h₁ h₂, absurd rfl h₂) (λ h₁ h₂, rfl) a
 
 end Three

tests/lean/run/example1.lean

@@ -8,7 +8,7 @@ namespace day
   definition next_weekday d :=
   rec_on d tuesday wednesday thursday friday monday monday monday
 
-  example test_next_weekday : next_weekday (next_weekday saturday) = tuesday :=
+  example : next_weekday (next_weekday saturday) = tuesday :=
   rfl
 
 end day