turn missing doc error into warning

server/test/test_statement.lean

@@ -5,10 +5,21 @@ Game "Test"
 World "TestW"
 Level 1
 
+/- Missing doc -/
+
+-- Shows warning on `foo.bar`:
+Statement foo.bar "some text" : 5 ≤ 7 := by
+  simp
+
+NewLemma foo.baz
+DisabledTactic tauto
+
+/- Other tests -/
+
 LemmaDoc add_zero as "add_zero" in "Nat" "(nothing)"
 
-@[simp] Statement add_zero "test" (n : Nat) : n + n = n := by
-  sorry
+Statement add_zero "test" (n : Nat) : n + 0 = n := by
+  rfl
 
 Statement (n : Nat) : 0 + n = n := by
   Template
@@ -23,5 +34,5 @@ NewLemma add_zero
 
 #print add_zero
 
-theorem xy (n : Nat) : n + n = n := by
+theorem xy (n : Nat) : n + 0 = n := by
   simp