Make sure all tests run with all features.

src/api.rs

@@ -274,6 +274,8 @@ impl<'e> Engine<'e> {
     ///
     /// ```rust
     /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # #[cfg(not(feature = "no_stdlib"))]
+    /// # {
     /// use rhai::Engine;
     ///
     /// let mut engine = Engine::new();
@@ -283,6 +285,7 @@ impl<'e> Engine<'e> {
     /// let result: i64 = engine.call_fn("add", &ast, (String::from("abc"), 123_i64))?;
     ///
     /// assert_eq!(result, 126);
+    /// # }
     /// # Ok(())
     /// # }
     /// ```

src/builtin.rs

@@ -479,7 +479,7 @@ impl Engine<'_> {
 
         reg_func1!(self, "debug", print_debug, String, i8, u8, i16, u16);
         reg_func1!(self, "debug", print_debug, String, i32, i64, u32, u64);
-        reg_func1!(self, "debug", print_debug, String, bool, char);
+        reg_func1!(self, "debug", print_debug, String, bool, char, String, ());
 
         #[cfg(not(feature = "no_float"))]
         {
@@ -490,7 +490,7 @@ impl Engine<'_> {
         #[cfg(not(feature = "no_index"))]
         {
             reg_func1!(self, "print", print_debug, String, Array);
-            reg_func1!(self, "debug", print_debug, String, String, Array, ());
+            reg_func1!(self, "debug", print_debug, String, Array);
 
             // Register array iterator
             self.register_iterator::<Array, _>(|a| {

src/optimize.rs

@@ -61,7 +61,7 @@ fn optimize_stmt(stmt: Stmt, changed: &mut bool) -> Stmt {
                 // Remove all raw expression statements that evaluate to constants
                 // except for the very last statement
                 result.retain(|stmt| match stmt {
-                    Stmt::Expr(expr) if expr.is_constant() => false,
+                    Stmt::Expr(expr) if expr.is_constant() || expr.is_identifier() => false,
                     _ => true,
                 });