Add meta methods, methods, functions, and field setters to UserData

src/function.rs

@@ -61,7 +61,7 @@ impl<'a> Function<'a> {
 }
 
 impl<'a> AsLua<'a> for Function<'a> {
-    fn as_lua(&self, lua: &'a State) -> crate::Result<crate::Value<'a>> {
+    fn as_lua(&self, _lua: &'a State) -> crate::Result<crate::Value<'a>> {
         Ok(crate::Value::Function(self.clone()))
     }
 }
@@ -135,6 +135,7 @@ macro_rules! impl_function_arg_tuple {
             }
         }
 
+        #[allow(non_snake_case)]
         impl<'a, $first: FromLuaStack<'a>, $($name: FromLuaStack<'a>,)+> FromLuaStackMulti<'a> for ($first, $($name,)+) {
             fn len() -> usize {
                 $count

src/main.rs

@@ -1,6 +1,5 @@
-use std::{any::type_name, ffi::CStr, marker::PhantomData, mem, ptr, str::Utf8Error, sync::Arc};
+use std::{marker::PhantomData, sync::Arc};
 
-use lua::{lua_typename, lua_type};
 use mlua_sys as lua;
 
 pub mod state;
@@ -90,8 +89,18 @@ fn main() -> Result<()> {
 
         print("Vec2: " .. dump_table(Vec2))
         print("Meta Vec2: " .. dump_table(getmetatable(Vec2)))
-        --local vec2 = Vec2.new(50, 50)
+        
         print("Vec2 is (" .. Vec2.x .. ", " .. Vec2.y .. ")")
+
+        local v1 = Vec2.new(50, 50)
+        print("v1 is (" .. v1.x .. ", " .. v1.y .. ")")
+
+        local v2 = Vec2.new(500, 500)
+        print("v2 is (" .. v2.x .. ", " .. v2.y .. ")")
+
+        local v_add = v1 + v2
+        v_add.x = 90
+        print("v_add is (" .. v_add.x .. ", " .. v_add.y .. ")")
     "#).unwrap();
 
     unsafe {
@@ -198,6 +207,12 @@ pub trait FromLuaStack<'a>: Sized {
     unsafe fn from_lua_stack(state: &'a State) -> Result<Self>;
 }
 
+impl<'a> PushToLuaStack<'a> for () {
+    unsafe fn push_to_lua_stack(&self, _state: &'a State) -> Result<()> {
+        Ok(())
+    }
+}
+
 /// Implements PushToLuaStack for a number
 macro_rules! impl_as_lua_number {
     ($ty: ident) => {
@@ -207,7 +222,7 @@ macro_rules! impl_as_lua_number {
             }
         }
 
-        impl FromLua for $ty {
+        impl<'a> FromLua<'a> for $ty {
             fn from_lua(_lua: &State, val: Value) -> crate::Result<Self> {
                 match val {
                     Value::Number(v) => Ok(v as $ty),
@@ -253,7 +268,7 @@ impl<'a> PushToLuaStack<'a> for String {
     }
 }
 
-impl<'a> FromLuaStack<'a> for String {
+/* impl<'a> FromLuaStack<'a> for String {
     unsafe fn from_lua_stack(state: &'a State) -> Result<Self> {
         let s = state.state_ptr();
 
@@ -263,6 +278,12 @@ impl<'a> FromLuaStack<'a> for String {
         let cstr = CStr::from_ptr(cstr);
         Ok(cstr.to_str().unwrap().to_string())
     }
+} */
+
+impl<'a> FromLua<'a> for String {
+    fn from_lua(_lua: &State, val: Value) -> crate::Result<Self> {
+        val.as_string().cloned()
+    }
 }
 
 impl<'a> PushToLuaStack<'a> for &str {
@@ -286,7 +307,23 @@ impl Userdata for Vec2 {
     fn build<'a>(builder: &mut UserdataBuilder<'a, Vec2>) -> crate::Result<()> {
         builder.name("Vec2")
             .field_getter("x", |_, this| Ok(this.x))
-            .field_getter("y", |_, this| Ok(this.y));
+            .field_getter("y", |_, this| Ok(this.y))
+            
+            .field_setter("x", |_, this, x: f32| this.x = x)
+            .field_setter("y", |_, this, y: f32| this.y = y)
+
+            .function("new", |lua, (x, y)| {
+                lua.create_userdata("Vec2", Vec2 { x, y, })
+            })
+            .meta_method(MetaMethod::Add, |lua, lhs: &Vec2, (rhs,): (&Vec2,)| {
+                let lx = lhs.x;
+                let ly = lhs.y;
+
+                let rx = rhs.x;
+                let ry = rhs.y;
+                
+                lua.create_userdata("Vec2", Vec2 { x: lx + rx, y: ly + ry, })
+            });
 
         Ok(())
     }
@@ -301,7 +338,7 @@ impl<T: Userdata> UserdataProxy<T> {
 }
 
 impl<'a, T: Userdata> AsLua<'a> for UserdataProxy<T> {
-    fn as_lua(&self, lua: &'a State) -> crate::Result<Value<'a>> {
+    fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
         todo!()
     }
 }
@@ -314,12 +351,12 @@ impl<T: Userdata> Userdata for UserdataProxy<T> {
 
         builder.name(&other.name.unwrap());
 
-        for (lbl, getters) in other.field_getters.into_iter() {
+        /* for (lbl, getters) in other.field_getters.into_iter() {
             let wrap = |state: &State, data: &Self| {
                 Ok(())
             };
             builder.field_getter(&lbl, wrap);
-        }
+        } */
 
         Ok(())
     }

src/state.rs

@@ -1,9 +1,9 @@
 use core::ffi;
-use std::{ffi::{CString, CStr}, mem, ptr::{self, NonNull}, str::Utf8Error};
+use std::{collections::HashMap, ffi::{CString, CStr}, mem, ptr::{self, NonNull}, str::Utf8Error};
 
 use mlua_sys as lua;
 
-use crate::{ensure_type, lua_error_guard, AnyUserdata, Error, FromLuaStack, FromLuaStackMulti, Function, LuaRef, PushToLuaStack, PushToLuaStackMulti, Result, StackGuard, Table, Userdata, UserdataBuilder, Value};
+use crate::{lua_error_guard, AnyUserdata, AsLua, Error, FromLuaStack, FromLuaVec, Function, LuaRef, MetaMethod, PushToLuaStack, PushToLuaStackMulti, Result, StackGuard, Table, Userdata, UserdataBuilder, Value, ValueVec};
 
 pub fn ptr_to_string(ptr: *const i8) -> std::result::Result<String, Utf8Error> {
     let c = unsafe { CStr::from_ptr(ptr) };
@@ -117,7 +117,12 @@ impl State {
             if lua::luaL_dostring(lua, text_c) != 0 {
                 let error_c = CStr::from_ptr(lua::lua_tostring(lua, -1));
                 let error_str = error_c.to_str()
-                    .expect("Error bytes are invalid!");
+                    .unwrap_or_else(|_| {
+                        let b = error_c.to_bytes();
+                        std::str::from_utf8_unchecked(b)
+                    });
+                    //.expect("Error bytes are invalid!");
+                //std::str::from
                 return Err(Error::runtime(error_str));
             }
         }
@@ -177,6 +182,7 @@ impl State {
         }
     }
 
+    #[allow(dead_code)]
     pub(crate) unsafe fn print_stack(state: &State) {
         let s = state.state_ptr();
         let t = lua::lua_gettop(s);
@@ -192,7 +198,7 @@ impl State {
 
     pub fn create_function<'a, A, R, F>(&self, f: F) -> Result<Function>
     where
-        A: FromLuaStackMulti<'a>,
+        A: FromLuaVec<'a>,
         R: PushToLuaStackMulti<'a>,
         F: Fn(&'a State, A) -> Result<R> + 'static,
     {
@@ -236,17 +242,13 @@ impl State {
             state: &'a State,
         }
 
-        let wrapper_fn = move |lua: &State, narg: i32| -> i32 {
+        let wrapper_fn = move |lua: &State, _narg: i32| -> i32 {
             unsafe {
                 let lua: &State = mem::transmute(lua); // transmute lifetimes
 
-                if narg != A::len() as i32 {
-                    Error::Runtime(format!("incorrect number of arguments provided to lua function, expected {}", A::len()))
-                        .throw_lua(lua.state_ptr());
-                }
-
                 lua_error_guard(lua, || {
-                    let args = A::results_from_lua_stack(lua)?;
+                    let vec = ValueVec::from_lua_stack(lua)?;
+                    let args = A::from_lua_value_vec(lua, vec)?;
 
                     let r = f(lua, args)?;
                     r.push_args_to_lua_stack(lua)?;
@@ -297,7 +299,6 @@ impl State {
 
                 // if the metatable is not made yet, make it
                 let mt = self.create_userdata_metatable::<T>()?;
-                //let mt = mt.get_metatable().unwrap(); // the table 100% has a metatable
                 mt.push_to_lua_stack(self)?;
             } else if ty != lua::LUA_TTABLE {
                 return Err(Error::RegistryConflict(name.to_string()));
@@ -314,21 +315,63 @@ impl State {
         T::build(&mut builder)?;
 
         let getters = builder.field_getters;
+        let setters = builder.field_setters;
         let name = builder.name.unwrap();
 
+        let mut fns_table = HashMap::new();
+        for (func_name, func) in builder.functions.into_iter() {
+            let lua_func = self.create_function(move |lua: &State, vals: ValueVec| {
+                func(lua, vals)
+            })?;
+            // Safety: This will be alive for as long as the lua state is alive
+            let lua_func: Function<'_> = unsafe { mem::transmute(lua_func) };
+            fns_table.insert(func_name, lua_func);
+        }
+
         let mt = self.create_meta_table(&name)?;
 
-        if !getters.is_empty() {
+        // dont create an index function if there are no getters,
+        // or if an index metamethod was defined
+        if !getters.is_empty() || !builder.meta_methods.contains_key("__index") {
             let index_fn = self.create_function(move |lua: &State, (ud, key): (AnyUserdata, String)| {
                 if let Some(getter) = getters.get(&key) {
-                    let r = getter(lua, Value::Userdata(ud))?;
+                    let r = getter(lua, ValueVec::from(Value::Userdata(ud)))?;
                     Ok(r)
+                } else if let Some(function) = fns_table.get(&key) {
+                    Ok(Value::Function(function.clone()))
                 } else {
                     Ok(Value::Nil)
                 }
             })?;
 
-            mt.set_meta("__index", index_fn)?;
+            mt.set_meta(MetaMethod::Index, index_fn)?;
+        }
+
+        // dont create an index function if there are no setters,
+        // or if a new index metamethod was defined
+        if !setters.is_empty() || !builder.meta_methods.contains_key("__newindex") {
+            let index_fn = self.create_function(move |lua: &State, (ud, key, val): (AnyUserdata, String, Value)| {
+                if let Some(setter) = setters.get(&key) {
+                    let mut vec = ValueVec::from(ud.as_lua(lua)?);
+                    vec.push_back(val);
+
+                    // ignore value result, the wrapper function doesn't return anything
+                    setter(lua, vec)?;
+                    
+                    Ok(Value::None)
+                } else {
+                    Ok(Value::Nil)
+                }
+            })?;
+
+            mt.set_meta(MetaMethod::NewIndex, index_fn)?;
+        }
+
+        for (mm_name, mm) in builder.meta_methods.into_iter() {
+            let mm_func = self.create_function(move |lua: &State, vals: ValueVec| {
+                mm(lua, vals)
+            })?;
+            mt.set_meta(mm_name, mm_func)?;
         }
 
         Ok(mt)

src/table.rs

@@ -1,6 +1,4 @@
 
-use std::{ffi::CStr, ops::Deref, sync::Arc};
-
 use mlua_sys as lua;
 
 use crate::{ensure_type, FromLuaStack, LuaRef, PushToLuaStack, Result, StackGuard, State};
@@ -165,7 +163,6 @@ impl<'a> Table<'a> {
             val.push_to_lua_stack(self.state)?;
 
             lua::lua_rawset(s, -3);
-            lua::lua_pop(self.state.state_ptr(), -1);
         }
 
         Ok(())

src/userdata.rs

@@ -1,12 +1,89 @@
-use std::{collections::HashMap, marker::PhantomData, sync::Arc};
+use std::{collections::HashMap, marker::PhantomData};
 
-use crate::{ensure_type, AsLua, FromLua, FromLuaStack, LuaRef, PushToLuaStack, State, Table, Value};
+use crate::{ensure_type, AsLua, FromLua, FromLuaStack, FromLuaVec, LuaRef, PushToLuaStack, State, Value, ValueVec};
 
 use mlua_sys as lua;
 
 //pub type FieldSetter<T> = fn(lua: &State, this: &T);
 //pub type FieldGetter<T, U> = fn(lua: &State, this: &T, val: &U);
 
+/// An enum representing all Lua MetaMethods
+/// https://gist.github.com/oatmealine/655c9e64599d0f0dd47687c1186de99f
+pub enum MetaMethod {
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Unm,
+    Mod,
+    Pow,
+    IDiv,
+    BAnd,
+    BOr,
+    BXOr,
+    BNot,
+    Shl,
+    Shr,
+    Eq,
+    Lt,
+    Le,
+    Concat,
+    Len,
+    Index,
+    NewIndex,
+    Call,
+    Mode,
+    Close,
+    Gc,
+    ToString,
+    Metatable,
+    Name,
+    Pairs,
+}
+
+impl AsRef<str> for MetaMethod {
+    fn as_ref(&self) -> &str {
+        match self {
+            MetaMethod::Add => "__add",
+            MetaMethod::Sub => "__sub",
+            MetaMethod::Mul => "__mul",
+            MetaMethod::Div => "__div",
+            MetaMethod::Unm => "__unm",
+            MetaMethod::Mod => "__mod",
+            MetaMethod::Pow => "__pow",
+            MetaMethod::IDiv => "__idiv",
+            MetaMethod::BAnd => "__band",
+            MetaMethod::BOr => "__bor",
+            MetaMethod::BXOr => "__bxor",
+            MetaMethod::BNot => "__bnot",
+            MetaMethod::Shl => "__shl",
+            MetaMethod::Shr => "__shr",
+            MetaMethod::Eq => "__eq",
+            MetaMethod::Lt => "__lt",
+            MetaMethod::Le => "__le",
+            MetaMethod::Concat => "__concat",
+            MetaMethod::Len => "__len",
+            MetaMethod::Index => "__index",
+            MetaMethod::NewIndex => "__newindex",
+            MetaMethod::Call => "__call",
+            MetaMethod::Mode => "__mode",
+            MetaMethod::Close => "__close",
+            MetaMethod::Gc => "__gc",
+            MetaMethod::ToString => "__tostring",
+            MetaMethod::Metatable => "__metatable",
+            MetaMethod::Name => "__name",
+            MetaMethod::Pairs => "__pairs",
+        }
+    }
+}
+
+impl<'a> PushToLuaStack<'a> for MetaMethod {
+    unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
+        let s = self.as_ref().to_string();
+        s.push_to_lua_stack(state)
+    }
+}
+
 pub trait FieldSetter {
     fn set_field(&self, val: Value);
 }
@@ -15,11 +92,14 @@ pub trait FieldGetter {
     fn get_field(&self) -> Value;
 }
 
-type UserdataFn<'a> = Box<dyn Fn(&'a State, Value<'a>) -> crate::Result<Value<'a>>>;
+type UserdataFn<'a> = Box<dyn Fn(&'a State, ValueVec<'a>) -> crate::Result<Value<'a>>>;
 
 pub struct UserdataBuilder<'a, T> {
     pub(crate) name: Option<String>,
     pub(crate) field_getters: HashMap<String, UserdataFn<'a>>,
+    pub(crate) field_setters: HashMap<String, UserdataFn<'a>>,
+    pub(crate) functions: HashMap<String, UserdataFn<'a>>,
+    pub(crate) meta_methods: HashMap<String, UserdataFn<'a>>,
     _marker: PhantomData<T>,
 }
 
@@ -28,6 +108,9 @@ impl<'a, T> UserdataBuilder<'a, T> {
         Self {
             name: None,
             field_getters: HashMap::new(),
+            field_setters: HashMap::new(),
+            functions: HashMap::new(),
+            meta_methods: HashMap::new(),
             _marker: PhantomData,
         }
     }
@@ -42,7 +125,8 @@ impl<'a, T> UserdataBuilder<'a, T> {
         F: Fn(&'a State, &T) -> crate::Result<R> + 'static,
         R: AsLua<'a>,
     {
-        let wrap = move |lua: &'a State, val: Value<'a>| {
+        let wrap = move |lua: &'a State, mut val: ValueVec<'a>| {
+            let val = val.pop_front().unwrap();
             let this = val.as_userdata().unwrap(); // if this panics, its a bug
             let this = this.as_ref::<T>()?;
             f(lua, this).and_then(|r| r.as_lua(lua))
@@ -52,68 +136,81 @@ impl<'a, T> UserdataBuilder<'a, T> {
         self
     }
 
-    pub fn into_meta_table(self, state: &'a State, table: &Table<'a>) -> crate::Result<()> {
+    pub fn field_setter<F, V>(&mut self, name: &str, f: F) -> &mut Self
-        //let this: Self = unsafe { std::mem::transmute(self) };
+    where
-        //let getters = *self.field_getters;
+        F: Fn(&'a State, &mut T, V) -> () + 'static,
+        V: FromLua<'a>,
+    {
+        let wrap = move |lua: &'a State, mut val: ValueVec<'a>| {
+            let lua_val = val.pop_front().unwrap();
+            let this = lua_val.as_userdata().unwrap(); // if this panics, its a bug
+            let this = this.as_mut::<T>()?;
 
-        /* let index_fn = state.create_function(move |lua: &'a State, (ud, key): (AnyUserdata<'a>, String)| {
+            let lua_val = val.pop_front().unwrap();
-            let ud_ref = ud.as_ref::<T>()?;
+            let v_arg = V::from_lua(lua, lua_val)?;
 
-            if let Some(getter) = self.field_getters.get(&key) {
+            f(lua, this, v_arg).as_lua(lua)
-                let r = getter(lua, ome(ud_ref), Value::Nil)?;
+        };
+        self.field_setters.insert(name.to_string(), Box::new(wrap));
 
-                let r = unsafe { std::mem::transmute(r) };
+        self
-
-                Ok(r)
-            } else {
-                //ud.get::<_, Value<'a>>(key)
-                Ok(Value::Nil)
-            }
-        })?;
-
-        table.set("__index", index_fn)?; */
-
-        Ok(())
     }
 
-    /* pub fn wrap_builder<U, F>(this: &mut UserdataBuilder<'a, T>, other: UserdataBuilder<'a, U>, to_proxied: F)
+    pub fn function<F, R, A>(&mut self, name: &str, f: F) -> &mut Self
     where
-        F: Fn(&'a T) -> &'a U + 'a,
+        F: Fn(&'a State, A) -> crate::Result<R> + 'static,
+        A: FromLuaVec<'a>,
+        R: AsLua<'a>,
     {
-        let to_proxied = Arc::new(to_proxied);
+        let wrap = move |lua: &'a State, val: ValueVec<'a>| {
-        for (lbl, getter) in other.field_getters.into_iter() {
+            let args = A::from_lua_value_vec(lua, val)?;
-            let to_proxied_cl = to_proxied.clone();
+            f(lua, args).and_then(|r| r.as_lua(lua))
-            let new_getter = move |lua: &'a State, this: Option<&T>, val: Value<'a>| {
+        };
-                let proxy = this.map(|t| to_proxied_cl(t));
+        self.functions.insert(name.to_string(), Box::new(wrap));
-                getter(lua, proxy, val)
-            };
-            this.field_getters.insert(lbl, Box::new(new_getter));
-        }
-    } */
 
-    /* pub fn into_userdata(self, state: &'a State, data: T) -> crate::Result<Table<'a>> {
+        self
-        let name = self.name
+    }
-            .expect("No name was set for userdata!");
 
-        let getters = self.field_getters.clone();
+    pub fn method<F, R, A>(&mut self, name: &str, f: F) -> &mut Self
-        let index_fn = state.create_function(move |lua: &'a State, (ud, key): (AnyUserdata<'a>, String)| {
+    where
-            let ud_ref = ud.as_ref::<T>()?;
+        F: Fn(&'a State, &T, A) -> crate::Result<R> + 'static,
+        A: FromLuaVec<'a>,
+        R: AsLua<'a>,
+    {
+        let wrap = move |lua: &'a State, mut val: ValueVec<'a>| {
+            let this_val = val.pop_front().unwrap();
+            let this = this_val.as_userdata().unwrap(); // if this panics, its a bug
+            let this = this.as_ref::<T>()?;
 
-            if let Some(getter) = getters.get(&key) {
+            let args = A::from_lua_value_vec(lua, val)?;
-                getter(lua, Some(ud_ref), Value::Nil)
-            } else {
-                //ud.get::<_, Value<'a>>(key)
-                Ok(Value::Nil)
-            }
             
-            //todo!()
+            f(lua, this, args).and_then(|r| r.as_lua(lua))
-        })?;
+        };
+        self.functions.insert(name.to_string(), Box::new(wrap));
 
-        let mt = state.create_meta_table(&name)?;
+        self
-        mt.set("__index", index_fn)?;
+    }
 
-        Ok(mt)
+    pub fn meta_method<N, F, R, A>(&mut self, name: N, f: F) -> &mut Self
-    } */
+    where
+        N: AsRef<str>,
+        F: Fn(&'a State, &T, A) -> crate::Result<R> + 'static,
+        A: FromLuaVec<'a>,
+        R: AsLua<'a>,
+    {
+        let wrap = move |lua: &'a State, mut val: ValueVec<'a>| {
+            let this_val = val.pop_front().unwrap();
+            let this = this_val.as_userdata().unwrap(); // if this panics, its a bug
+            let this = this.as_ref::<T>()?;
+
+            let args = A::from_lua_value_vec(lua, val)?;
+            
+            f(lua, this, args).and_then(|r| r.as_lua(lua))
+        };
+        self.meta_methods.insert(name.as_ref().to_string(), Box::new(wrap));
+
+        self
+    }
 }
 
 pub trait Userdata: Sized {
@@ -141,7 +238,17 @@ impl<'a> AnyUserdata<'a> {
 
             self.lref.push_to_lua_stack(self.state)?;
             let cptr = lua::lua_touserdata(s, -1);
-            Ok(cptr.cast::<T>().as_ref().unwrap())
+            Ok(cptr.cast::<T>().as_ref().unwrap()) // TODO: Ensure this userdata matches the type of T
+        }
+    }
+
+    pub fn as_mut<T>(&self) -> crate::Result<&'a mut T> {
+        unsafe {
+            let s = self.state.state_ptr();
+
+            self.lref.push_to_lua_stack(self.state)?;
+            let cptr = lua::lua_touserdata(s, -1);
+            Ok(cptr.cast::<T>().as_mut().unwrap()) // TODO: Ensure this userdata matches the type of T
         }
     }
 }
@@ -162,3 +269,22 @@ impl<'a> PushToLuaStack<'a> for AnyUserdata<'a> {
         self.lref.push_to_lua_stack(state)
     }
 }
+
+impl<'a> AsLua<'a> for AnyUserdata<'a> {
+    fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
+        Ok(Value::Userdata(self.clone()))
+    }
+}
+
+impl<'a> FromLua<'a> for AnyUserdata<'a> {
+    fn from_lua(_lua: &State, val: Value<'a>) -> crate::Result<Self> {
+        val.into_userdata()
+    }
+}
+
+impl<'a, T: Userdata> FromLua<'a> for &'a T {
+    fn from_lua(_lua: &'a State, val: Value<'a>) -> crate::Result<Self> {
+        let ud = val.into_userdata()?;
+        ud.as_ref::<T>()
+    }
+}

src/util.rs

@@ -22,8 +22,6 @@ pub unsafe fn ensure_type(state: &State, typ: i32, idx: i32) -> crate::Result<()
         let s = cstr.to_str()
             .expect("Lua type has invalid bytes!");
 
-        println!("ty = {}, typ = {}", lua_type, typ);
-
         Err(crate::Error::UnexpectedType(exp_s.to_string(), s.to_string()))
     }
 }

src/value.rs

@@ -1,4 +1,4 @@
-use std::ffi::CStr;
+use std::{collections::VecDeque, ffi::CStr, ops::{Deref, DerefMut}};
 
 use crate::{AnyUserdata, FromLuaStack, Function, PushToLuaStack, State, Table};
 
@@ -6,6 +6,9 @@ use mlua_sys as lua;
 
 #[derive(Clone)]
 pub enum Value<'a> {
+    /// A None value means that nothing will be pushed to the lua stack.
+    /// This is different than Nil, which does get pushed to the stack.
+    None,
     Nil,
     Number(f64),
     String(String),
@@ -21,6 +24,7 @@ impl<'a> Value<'a> {
 
     pub fn type_name(&self) -> &'static str {
         match self {
+            Value::None => "None",
             Value::Nil => "Nil",
             Value::Number(_) => "Number",
             Value::String(_) => "String",
@@ -38,6 +42,27 @@ impl<'a> Value<'a> {
             }
         }
     }
+
+    /// Consumes self, and attempts to get `AnyUserdata`.
+    /// 
+    /// Returns an error if this value is not userdata
+    pub fn into_userdata(self) -> crate::Result<AnyUserdata<'a>> {
+        match self {
+            Value::Userdata(ud) => Ok(ud),
+            _ => {
+                Err(crate::Error::UnexpectedType("Userdata".to_string(), self.type_name().to_string()))
+            }
+        }
+    }
+
+    pub fn as_string(&self) -> crate::Result<&String> {
+        match self {
+            Value::String(s) => Ok(s),
+            _ => {
+                Err(crate::Error::UnexpectedType("String".to_string(), self.type_name().to_string()))
+            }
+        }
+    }
 }
 
 impl<'a> PushToLuaStack<'a> for Value<'a> {
@@ -45,6 +70,9 @@ impl<'a> PushToLuaStack<'a> for Value<'a> {
         let s = state.state_ptr();
 
         match self {
+            Value::None => {
+
+            },
             Value::Nil => {
                 state.ensure_stack(1)?;
                 lua::lua_pushnil(s);
@@ -103,6 +131,10 @@ impl<'a> FromLuaStack<'a> for Value<'a> {
                 Table::from_lua_stack(state)
                     .map(|t| Value::Table(t))
             },
+            lua::LUA_TUSERDATA => {
+                AnyUserdata::from_lua_stack(state)
+                    .map(|ud| Value::Userdata(ud))
+            },
             _ => {
                 let s = lua::lua_typename(s, ty);
                 let s = CStr::from_ptr(s);
@@ -119,32 +151,121 @@ pub trait AsLua<'a> {
     fn as_lua(&self, lua: &'a State) -> crate::Result<Value<'a>>;
 }
 
-pub trait FromLua: Sized {
+pub trait FromLua<'a>: Sized {
-    fn from_lua(lua: &State, val: Value) -> crate::Result<Self>;
+    fn from_lua(lua: &'a State, val: Value<'a>) -> crate::Result<Self>;
-}
-
-/* impl<'a> AsLua<'a> for Value<'a> {
-    fn as_lua(&self, lua: &'a State) -> crate::Result<Value<'a>> {
-        Ok(self.clone())
-    }
-} */
-
-/* impl<'a, T: AsLua<'a>> PushToLuaStack<'a> for T {
-    unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
-        let v = self.as_lua(state)?;
-        v.push_to_lua_stack(state)
-    }
-}
- */
-impl<'a, T: FromLua> FromLuaStack<'a> for T {
-    unsafe fn from_lua_stack(state: &'a State) -> crate::Result<Self> {
-        let v = Value::from_lua_stack(state)?;
-        T::from_lua(state, v)
-    }
 }
 
 impl<'a> AsLua<'a> for () {
-    fn as_lua(&self, lua: &'a State) -> crate::Result<Value<'a>> {
+    fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
         Ok(Value::Nil)
     }
 }
+
+impl<'a> FromLua<'a> for Value<'a> {
+    fn from_lua(_lua: &'a State, val: Value<'a>) -> crate::Result<Self> {
+        Ok(val)
+    }
+}
+
+#[derive(Default)]
+pub struct ValueVec<'a>(VecDeque<Value<'a>>);
+
+impl<'a> Deref for ValueVec<'a> {
+    type Target = VecDeque<Value<'a>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<'a> DerefMut for ValueVec<'a> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl<'a> FromLuaStack<'a> for ValueVec<'a> {
+    unsafe fn from_lua_stack(state: &'a State) -> crate::Result<Self> {
+        let s = state.state_ptr();
+
+        let top = lua::lua_gettop(s);
+
+        let mut vec = VecDeque::new();
+        for _ in 1..(top + 1) {
+            let v = Value::from_lua_stack(state)?;
+            vec.push_front(v);
+        }
+
+        Ok(ValueVec(vec))
+    }
+}
+
+impl<'a> ValueVec<'a> {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl<'a> From<Value<'a>> for ValueVec<'a> {
+    fn from(value: Value<'a>) -> Self {
+        let mut v = VecDeque::new();
+        v.push_back(value);
+        ValueVec(v)
+    }
+}
+
+/// A trait for getting something from a ValueVec from Lua
+pub trait FromLuaVec<'a>: Sized {
+    fn from_lua_value_vec(state: &'a State, values: ValueVec<'a>) -> crate::Result<Self>;
+}
+
+impl<'a> FromLuaVec<'a> for () {
+    fn from_lua_value_vec(_state: &'a State, _values: ValueVec<'a>) -> crate::Result<Self> {
+        Ok(())
+    }
+}
+
+impl<'a> FromLuaVec<'a> for ValueVec<'a> {
+    fn from_lua_value_vec(_state: &'a State, values: ValueVec<'a>) -> crate::Result<Self> {
+        Ok(values)
+    }
+}
+
+macro_rules! impl_from_lua_vec_tuple {
+    ( $count: expr, $first: tt, $( $name: tt ),+ ) => (
+        #[allow(non_snake_case)]
+        impl<'a, $first: FromLua<'a>, $($name: FromLua<'a>,)+> FromLuaVec<'a> for ($first, $($name,)+) {
+      
+            fn from_lua_value_vec(state: &'a State, mut values: ValueVec<'a>) -> crate::Result<Self> {
+                if values.len() != $count {
+                    panic!("Not same length"); // TODO
+                }
+
+                let f = $first::from_lua(state, values.pop_front().unwrap())?;
+                let ($( $name, )+) = ( $( $name::from_lua(state, values.pop_front().unwrap())?, )+ );
+
+                Ok( (f, $( $name, )+) )
+            }
+        }
+
+        impl_from_lua_vec_tuple!( $count - 1, $( $name ),+ );
+    );
+
+    ( $count: expr, $only: tt ) => {
+        #[allow(non_snake_case)]
+        impl<'a, $only: FromLua<'a>> FromLuaVec<'a> for ($only,) {
+            fn from_lua_value_vec(state: &'a State, mut values: ValueVec<'a>) -> crate::Result<Self> {
+                if values.len() != 1 {
+                    panic!("Not same length"); // TODO
+                }
+
+                Ok( ( $only::from_lua(state, values.pop_front().unwrap())?, ) )
+            }
+        }
+    };
+
+}
+
+// hopefully 16 is more than enough
+// if you have 16 function results, and need more than 16, you NEED help
+impl_from_lua_vec_tuple! { 16, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16 }