Allow script functions to override built-in functions.

src/builtin.rs

@@ -195,14 +195,12 @@ impl Engine {
         fn print<T: Display>(x: T) -> String {
             format!("{}", x)
         }
-        fn println() -> String {
-            "\n".to_string()
-        }
 
         reg_func1!(self, "print", print, String, i32, i64, u32, u64);
         reg_func1!(self, "print", print, String, f32, f64, bool, char, String);
         reg_func1!(self, "print", print_debug, String, Array);
-        self.register_fn("print", println);
+        self.register_fn("print", || "".to_string());
+        self.register_fn("print", |_: ()| "".to_string());
 
         reg_func1!(self, "debug", print_debug, String, i32, i64, u32, u64);
         reg_func1!(self, "debug", print_debug, String, f32, f64, bool, char);

src/engine.rs

@@ -244,29 +244,17 @@ impl Engine {
                 .collect::<Vec<_>>()
         );
 
-        let spec = FnSpec {
+        let mut spec = FnSpec {
             ident: ident.clone(),
-            args: Some(args.iter().map(|a| Any::type_id(&**a)).collect()),
+            args: None,
         };
 
         // First search in script-defined functions (can override built-in),
-        // then in built-in's, then retry again with no arguments
+        // then in built-in's
-        let fn_def = self
+        let fn_def = self.script_fns.get(&spec).or_else(|| {
-            .script_fns
+            spec.args = Some(args.iter().map(|a| Any::type_id(&**a)).collect());
-            .get(&spec)
+            self.fns.get(&spec)
-            .or_else(|| self.fns.get(&spec))
+        });
-            .or_else(|| {
-                self.script_fns.get(&FnSpec {
-                    ident: ident.clone(),
-                    args: None,
-                })
-            })
-            .or_else(|| {
-                self.fns.get(&FnSpec {
-                    ident: ident.clone(),
-                    args: None,
-                })
-            });
 
         if let Some(f) = fn_def {
             match **f {