Add Nil constructor and tests

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/builtins.rs

@@ -569,3 +569,13 @@ impl Bool {
         Float::create(bool_value as i64 as f64).into()
     }
 }
+
+impl Nil {
+    pub(crate) fn do_call(_vm: &mut Vm, _state: FunctionState) -> FunctionResult {
+        FunctionResult::ReturnPush(Nil::create())
+    }
+
+    pub(crate) fn init(_vm: &mut Vm, _state: FunctionState) -> FunctionResult {
+        FunctionResult::ReturnPush(Nil::create())
+    }
+}

src/obj.rs

@@ -221,7 +221,15 @@ pub fn init_types() {
 
             // Operators
         },
-        Nil { },
+        Nil {
+            // Conversion methods
+
+            // Constructor
+            __call__ => BuiltinFunction::create("__call__", Nil::do_call, 1),
+            __init__ => BuiltinFunction::create("__init__", Nil::init, 1),
+
+            // Operators
+        },
         BuiltinFunction { },
         UserFunction { },
         Method { },

tests/bool.npp

@@ -70,3 +70,4 @@ println(Bool("true"))
 println(Bool(1))
 println(Bool(1.0))
 println(Bool(true))
+println(Bool(nil))

tests/bool.npp.expect

@@ -53,3 +53,4 @@ true
 true
 true
 true
+false

tests/nil.npp

@@ -0,0 +1,16 @@
+# Nil type operator and function tests
+
+a = nil
+
+println("__not__")
+println(!nil)
+println(!!nil)
+
+println("__eq__")
+println(nil == nil)
+
+println("__ne__")
+println(nil != nil)
+
+println("constructor")
+println(Nil())

tests/nil.npp.expect

@@ -0,0 +1,9 @@
+__not__
+true
+false
+__eq__
+true
+__ne__
+false
+constructor
+nil