Move NativeCallableParamSpec init for &Arguments into __derive_refs

Summary: Generally it's better to move code outside of generated into `__derive_refs` if it does not affect performance or compilation speed.

Reviewed By: JakobDegen

Differential Revision: D63598693

fbshipit-source-id: 4d88825b90e46693b580680fbd2f0682416bf006

2 files changed, 12 insertions, 19 deletions

diff --git a/starlark/src/__derive_refs/param_spec.rs b/starlark/src/__derive_refs/param_spec.rs
index f6dbf787..f1cf12e1 100644
--- a/starlark/src/__derive_refs/param_spec.rs
+++ b/starlark/src/__derive_refs/param_spec.rs
@@ -74,6 +74,17 @@ pub struct NativeCallableParamSpec {
 }
 
 impl NativeCallableParamSpec {
+    /// For a function accepting raw `&Arguments`.
+    pub fn for_arguments() -> NativeCallableParamSpec {
+        NativeCallableParamSpec {
+            pos_only: Vec::new(),
+            pos_or_named: Vec::new(),
+            args: Some(NativeCallableParam::args("args", Ty::any())),
+            named_only: Vec::new(),
+            kwargs: Some(NativeCallableParam::kwargs("kwargs", Ty::any())),
+        }
+    }
+
     pub(crate) fn param_spec(&self) -> ParamSpec {
         ParamSpec::new_parts(
             self.pos_only.iter().map(|p| (p.is_required(), p.ty.dupe())),
diff --git a/starlark_derive/src/module/render/fun.rs b/starlark_derive/src/module/render/fun.rs
index 06ce0f7c..03934c39 100644
--- a/starlark_derive/src/module/render/fun.rs
+++ b/starlark_derive/src/module/render/fun.rs
@@ -584,26 +584,8 @@ fn render_native_callable_components(x: &StarFun) -> syn::Result<TokenStream> {
     };
 
     let param_spec: syn::Expr = if x.is_arguments() {
-        let args: syn::Expr = syn::parse_quote! {
-            starlark::__derive_refs::param_spec::NativeCallableParam::args(
-                "args",
-                starlark::typing::Ty::any()
-            )
-        };
-        let kwargs: syn::Expr = syn::parse_quote! {
-            starlark::__derive_refs::param_spec::NativeCallableParam::kwargs(
-                "kwargs",
-                starlark::typing::Ty::any()
-            )
-        };
         syn::parse_quote! {
-            starlark::__derive_refs::param_spec::NativeCallableParamSpec {
-                pos_only: vec![],
-                pos_or_named: vec![],
-                args: std::option::Option::Some(#args),
-                named_only: vec![],
-                kwargs: std::option::Option::Some(#kwargs),
-            }
+            starlark::__derive_refs::param_spec::NativeCallableParamSpec::for_arguments()
         }
     } else {
         let ParamSpec {