Remove unbox/cast step in eval

examples/custom_types_and_methods.rs

@@ -24,7 +24,7 @@ fn main() {
     engine.register_fn("update", TestStruct::update);
     engine.register_fn("new_ts", TestStruct::new);
 
-    if let Ok(result) = engine.eval("var x = new_ts(); x.update(); x").unwrap().downcast::<TestStruct>() {
+    if let Ok(result) = engine.eval::<TestStruct>("var x = new_ts(); x.update(); x") {
         println!("result: {}", result.x); // prints 1001
     }
 }

examples/hello.rs

@@ -4,7 +4,7 @@ use rhai::Engine;
 fn main() {
     let mut engine = Engine::new();
 
-    if let Ok(result) = engine.eval("40 + 2").unwrap().downcast::<i32>() {
-        println!("Answer: {}", *result);  // prints 42
+    if let Ok(result) = engine.eval::<i32>("40 + 2") {
+        println!("Answer: {}", result);  // prints 42
     }
 }

examples/reuse_scope.rs

@@ -5,9 +5,9 @@ fn main() {
     let mut engine = Engine::new();
     let mut scope: Scope = Vec::new();
 
-    if let Ok(_) = engine.eval_with_scope(&mut scope, "var x = 4 + 5") { } else { assert!(false); }    
+    if let Ok(_) = engine.eval_with_scope::<()>(&mut scope, "var x = 4 + 5") { } else { assert!(false); }    
 
-    if let Ok(result) = engine.eval_with_scope(&mut scope, "x").unwrap().downcast::<i32>() {
+    if let Ok(result) = engine.eval_with_scope::<i32>(&mut scope, "x") {
        println!("result: {}", result);
     }
 }

examples/rhai_runner.rs

@@ -27,7 +27,7 @@ fn main() {
             let mut contents = String::new();
             
             if let Ok(_) = f.read_to_string(&mut contents) {
-                match engine.eval(&contents) {
+                match engine.eval::<()>(&contents) {
                     Ok(_) => (),
                     Err(e) => {println!("Error: {:?}", e)}
                 }

examples/simple_fn.rs

@@ -10,7 +10,7 @@ fn main() {
 
     engine.register_fn("add", add);
  
-    if let Ok(result) = engine.eval("add(40, 2)").unwrap().downcast::<i32>() {
-       println!("Answer: {}", *result);  // prints 42
+    if let Ok(result) = engine.eval::<i32>("add(40, 2)") {
+       println!("Answer: {}", result);  // prints 42
     }
 }