Rename ArgTarget -> ApiParam

godot-core/src/builtin/collections/array.rs

@@ -12,8 +12,8 @@ use crate::builtin::*;
 use crate::meta;
 use crate::meta::error::{ConvertError, FromGodotError, FromVariantError};
 use crate::meta::{
-    ArgTarget, ArrayElement, ArrayTypeInfo, AsArg, CowArg, FromGodot, GodotConvert,
-    GodotFfiVariant, GodotType, PropertyHintInfo, RefArg, ToGodot,
+    ApiParam, ArrayElement, ArrayTypeInfo, AsArg, CowArg, FromGodot, GodotConvert, GodotFfiVariant,
+    GodotType, PropertyHintInfo, RefArg, ToGodot,
 };
 use crate::registry::property::{Export, Var};
 use godot_ffi as sys;
@@ -944,7 +944,7 @@ impl<'r, T: ArrayElement> AsArg<Array<T>> for &'r Array<T> {
     }
 }
 
-impl<T: ArrayElement> ArgTarget for Array<T> {
+impl<T: ArrayElement> ApiParam for Array<T> {
     type Arg<'v> = CowArg<'v, Self>;
 
     fn value_to_arg<'v>(self) -> Self::Arg<'v> {
@@ -1221,7 +1221,7 @@ impl<T: ArrayElement + ToGodot> Extend<T> for Array<T> {
         // A faster implementation using `resize()` and direct pointer writes might still be possible.
         // Note that this could technically also use iter(), since no moves need to happen (however Extend requires IntoIterator).
         for item in iter.into_iter() {
-            self.push(ArgTarget::value_to_arg(item));
+            self.push(ApiParam::value_to_arg(item));
         }
     }
 }

godot-core/src/builtin/collections/packed_array.rs

@@ -491,7 +491,7 @@ macro_rules! impl_packed_array {
                 // A faster implementation using `resize()` and direct pointer writes might still be
                 // possible.
                 for item in iter.into_iter() {
-                    self.push(meta::ArgTarget::value_to_arg(item));
+                    self.push(meta::ApiParam::value_to_arg(item));
                 }
             }
         }

godot-core/src/meta/as_arg.rs

@@ -6,7 +6,7 @@
  */
 
 use crate::builtin::{GString, NodePath, StringName};
-use crate::meta::CowArg;
+use crate::meta::{CowArg, GodotType};
 use std::ffi::CStr;
 
 /// Implicit conversions for arguments passed to Godot APIs.
@@ -23,7 +23,7 @@ use std::ffi::CStr;
 /// Implicitly converting from `T` for by-ref builtins is explicitly not supported. This emphasizes that there is no need to consume the object,
 /// thus discourages unnecessary cloning.
 ///
-/// If you need to pass owned values in generic code, you can use [`ArgTarget::value_to_arg()`].
+/// If you need to pass owned values in generic code, you can use [`ApiParam::value_to_arg()`].
 ///
 /// # Performance for strings
 /// Godot has three string types: [`GString`], [`StringName`] and [`NodePath`]. Conversions between those three, as well as between `String` and
@@ -37,18 +37,25 @@ use std::ffi::CStr;
 ///
 /// If you want to convert between Godot's string types for the sake of argument passing, each type provides an `arg()` method, such as
 /// [`GString::arg()`]. You cannot use this method in other contexts.
+///
+/// # Using the trait
+/// `AsArg` is meant to be used from the function call site, not the declaration site. If you declare a parameter as `impl AsArg<...>` yourself,
+/// you can only forward it as-is to a Godot API -- there are no stable APIs to access the inner object yet.
+///
+/// Furthermore, there is currently no benefit in implementing `AsArg` for your own types, as it's only used by Godot APIs which don't accept
+/// custom types. Classes are already supported through upcasting and [`AsObjectArg`][crate::obj::AsObjectArg].
 #[diagnostic::on_unimplemented(
     message = "Argument of type `{Self}` cannot be passed to an `impl AsArg<{T}>` parameter",
     note = "If you pass by value, consider borrowing instead.",
     note = "GString/StringName/NodePath aren't implicitly convertible for performance reasons; use their `arg()` method.",
     note = "See also `AsArg` docs: https://godot-rust.github.io/docs/gdext/master/godot/meta/trait.AsArg.html"
 )]
-pub trait AsArg<T: ArgTarget>
+pub trait AsArg<T: ApiParam>
 where
     Self: Sized,
 {
     #[doc(hidden)]
-    fn into_arg<'r>(self) -> <T as ArgTarget>::Arg<'r>
+    fn into_arg<'r>(self) -> <T as ApiParam>::Arg<'r>
     where
         Self: 'r;
 }
@@ -70,7 +77,7 @@ macro_rules! arg_into_ref {
     };
     ($arg_variable:ident: $T:ty) => {
         let $arg_variable = $arg_variable.into_arg();
-        let $arg_variable: &$T = $crate::meta::ArgTarget::arg_to_ref(&$arg_variable);
+        let $arg_variable: &$T = $crate::meta::ApiParam::arg_to_ref(&$arg_variable);
     };
 }
 
@@ -82,21 +89,21 @@ macro_rules! arg_into_owned {
     ($arg_variable:ident) => {
         let $arg_variable = $arg_variable.into_arg();
         let $arg_variable = $arg_variable.cow_into_owned();
-        // cow_into_owned() is not yet used generically; could be abstracted in ArgTarget::arg_to_owned() as well.
+        // cow_into_owned() is not yet used generically; could be abstracted in ApiParam::arg_to_owned() as well.
     };
 }
 
 #[macro_export]
 macro_rules! impl_asarg_by_value {
     ($T:ty) => {
         impl $crate::meta::AsArg<$T> for $T {
-            fn into_arg<'r>(self) -> <$T as $crate::meta::ArgTarget>::Arg<'r> {
+            fn into_arg<'r>(self) -> <$T as $crate::meta::ApiParam>::Arg<'r> {
                 // Moves value (but typically a Copy type).
                 self
             }
         }
 
-        impl $crate::meta::ArgTarget for $T {
+        impl $crate::meta::ApiParam for $T {
             type Arg<'v> = $T;
 
             fn value_to_arg<'v>(self) -> Self::Arg<'v> {
@@ -121,15 +128,15 @@ macro_rules! impl_asarg_by_ref {
             // Thus, keep `where` on same line.
             // type ArgType<'v> = &'v $T where Self: 'v;
 
-            fn into_arg<'cow>(self) -> <$T as $crate::meta::ArgTarget>::Arg<'cow>
+            fn into_arg<'cow>(self) -> <$T as $crate::meta::ApiParam>::Arg<'cow>
             where
                 'r: 'cow, // Original reference must be valid for at least as long as the returned cow.
             {
                 $crate::meta::CowArg::Borrowed(self)
             }
         }
 
-        impl $crate::meta::ArgTarget for $T {
+        impl $crate::meta::ApiParam for $T {
             type Arg<'v> = $crate::meta::CowArg<'v, $T>;
 
             fn value_to_arg<'v>(self) -> Self::Arg<'v> {
@@ -150,11 +157,11 @@ macro_rules! declare_arg_method {
         ///
         /// # Generic bounds
         /// The bounds are implementation-defined and may change at any time. Do not use this function in a generic context requiring `T`
-        /// -- use the `From` trait or [`ArgTarget`][crate::meta::ArgTarget] in that case.
+        /// -- use the `From` trait or [`ApiParam`][crate::meta::ApiParam] in that case.
         pub fn arg<T>(&self) -> impl $crate::meta::AsArg<T>
         where
             for<'a> T: From<&'a Self>
-                + $crate::meta::ArgTarget<Arg<'a> = $crate::meta::CowArg<'a, T>>
+                + $crate::meta::ApiParam<Arg<'a> = $crate::meta::CowArg<'a, T>>
                 + 'a,
         {
             $crate::meta::CowArg::Owned(T::from(self))
@@ -171,7 +178,7 @@ macro_rules! declare_arg_method {
 /// This is necessary for packed array dispatching to different "inner" backend signatures.
 impl<'a, T> AsArg<T> for CowArg<'a, T>
 where
-    for<'r> T: ArgTarget<Arg<'r> = CowArg<'r, T>> + 'r,
+    for<'r> T: ApiParam<Arg<'r> = CowArg<'r, T>> + 'r,
 {
     fn into_arg<'r>(self) -> CowArg<'r, T>
     where
@@ -181,7 +188,7 @@ where
     }
 }
 
-// impl<'a, T> ArgTarget for CowArg<'a, T> {
+// impl<'a, T> ApiParam for CowArg<'a, T> {
 //     type Type<'v> = CowArg<'v, T>
 //         where Self: 'v;
 // }
@@ -243,7 +250,8 @@ impl AsArg<NodePath> for &String {
 // ----------------------------------------------------------------------------------------------------------------------------------------------
 
 /// Implemented for all parameter types `T` that are allowed to receive [impl `AsArg<T>`][AsArg].
-pub trait ArgTarget
+pub trait ApiParam: GodotType
+// GodotType bound not required right now, but conceptually should always be the case.
 where
     Self: Sized,
 {

godot-core/src/meta/cow_arg.rs

@@ -47,7 +47,7 @@ impl<'r, T> CowArg<'r, T> {
     }
 }
 
-/// Exists for polymorphism in [`crate::meta::ArgTarget`].
+/// Exists for polymorphism in [`crate::meta::ApiParam`].
 ///
 /// Necessary for generics in e.g. `Array<T>`, when accepting `impl AsArg<T>` parameters.
 ///

godot-core/src/meta/traits.rs

@@ -162,7 +162,7 @@ pub trait GodotType: GodotConvert<Via = Self> + sealed::Sealed + Sized + 'static
     message = "`Array<T>` can only store element types supported in Godot arrays (no nesting).",
     label = "has invalid element type"
 )]
-pub trait ArrayElement: GodotType + ToGodot + FromGodot + sealed::Sealed + meta::ArgTarget {
+pub trait ArrayElement: GodotType + ToGodot + FromGodot + sealed::Sealed + meta::ApiParam {
     /// Returns the representation of this type as a type string.
     ///
     /// Used for elements in arrays (the latter despite `ArrayElement` not having a direct relation).

godot-core/src/obj/gd.rs

@@ -16,7 +16,7 @@ use crate::builtin::{Callable, NodePath, StringName, Variant};
 use crate::global::PropertyHint;
 use crate::meta::error::{ConvertError, FromFfiError};
 use crate::meta::{
-    ArgTarget, ArrayElement, AsArg, CallContext, ClassName, CowArg, FromGodot, GodotConvert,
+    ApiParam, ArrayElement, AsArg, CallContext, ClassName, CowArg, FromGodot, GodotConvert,
     GodotType, PropertyHintInfo, RefArg, ToGodot,
 };
 use crate::obj::{
@@ -781,7 +781,7 @@ impl<'r, T: GodotClass> AsArg<Gd<T>> for &'r Gd<T> {
     }
 }
 
-impl<T: GodotClass> ArgTarget for Gd<T> {
+impl<T: GodotClass> ApiParam for Gd<T> {
     type Arg<'v> = CowArg<'v, Gd<T>>;
 
     fn value_to_arg<'v>(self) -> Self::Arg<'v> {
@@ -803,7 +803,7 @@ impl<'r, T: GodotClass> AsArg<Option<Gd<T>>> for Option<&'r Gd<T>> {
     }
 }
 
-impl<T: GodotClass> ArgTarget for Option<Gd<T>> {
+impl<T: GodotClass> ApiParam for Option<Gd<T>> {
     type Arg<'v> = CowArg<'v, Option<Gd<T>>>;
 
     fn value_to_arg<'v>(self) -> Self::Arg<'v> {