From 1cfba4d4cc88bc861de53f0c3c645f5c9eb7198d Mon Sep 17 00:00:00 2001
From: Icxolu <10486322+Icxolu@users.noreply.github.com>
Date: Wed, 6 Mar 2024 23:34:53 +0100
Subject: [PATCH] deprecate `&PyModule` as `#[pymodule]` argument type

---
 pyo3-macros-backend/src/module.rs | 25 ++++++++++++++++++--
 src/impl_/pymethods.rs            | 39 +++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/pyo3-macros-backend/src/module.rs b/pyo3-macros-backend/src/module.rs
index 7173fa8647d..54367138783 100644
--- a/pyo3-macros-backend/src/module.rs
+++ b/pyo3-macros-backend/src/module.rs
@@ -7,7 +7,7 @@ use crate::{
     pyfunction::{impl_wrap_pyfunction, PyFunctionOptions},
 };
 use proc_macro2::TokenStream;
-use quote::quote;
+use quote::{quote, quote_spanned};
 use syn::{
     ext::IdentExt,
     parse::{Parse, ParseStream},
@@ -295,8 +295,29 @@ pub fn pymodule_function_impl(mut function: syn::ItemFn) -> Result<TokenStream>
     }
     module_args.push(quote!(::std::convert::Into::into(BoundRef(module))));
 
+    let syn::ItemFn {
+        attrs, sig, block, ..
+    } = &function;
+
+    let extractors = sig.inputs.iter().filter_map(|param| {
+        if let syn::FnArg::Typed(pat_type) = param {
+            if let syn::Pat::Ident(pat_ident) = &*pat_type.pat {
+                let ident = &pat_ident.ident;
+                return Some(quote_spanned! { pat_type.span() => {
+                    let (_, e) = #pyo3_path::impl_::pymethods::inspect_type(#ident);
+                    let _ = e.extract_gil_ref();
+                }});
+            }
+        }
+        None
+    });
+
     Ok(quote! {
-        #function
+        #(#attrs)*
+        #vis #sig {
+            #(#extractors)*
+            #block
+        }
         #vis mod #ident {
             #initialization
         }
diff --git a/src/impl_/pymethods.rs b/src/impl_/pymethods.rs
index df89dba7dbd..c63f3e88055 100644
--- a/src/impl_/pymethods.rs
+++ b/src/impl_/pymethods.rs
@@ -580,3 +580,42 @@ pub unsafe fn tp_new_impl<T: PyClass>(
         .create_class_object_of_type(py, target_type)
         .map(Bound::into_ptr)
 }
+
+pub fn inspect_type<T>(t: T) -> (T, Extractor<T>) {
+    (t, Extractor::new())
+}
+
+pub struct Extractor<T>(NotAGilRef<T>);
+pub struct NotAGilRef<T>(std::marker::PhantomData<T>);
+
+pub trait IsGilRef {}
+
+impl<T: crate::PyNativeType> IsGilRef for &'_ T {}
+
+impl<T> Extractor<T> {
+    pub fn new() -> Self {
+        Extractor(NotAGilRef(std::marker::PhantomData))
+    }
+}
+
+impl<T: IsGilRef> Extractor<T> {
+    #[cfg_attr(
+        not(feature = "gil-refs"),
+        deprecated(
+            since = "0.21.0",
+            note = "use `&Bound<'_, T>` instead for this function argument"
+        )
+    )]
+    pub fn extract_gil_ref(&self) {}
+}
+
+impl<T> NotAGilRef<T> {
+    pub fn extract_gil_ref(&self) {}
+}
+
+impl<T> std::ops::Deref for Extractor<T> {
+    type Target = NotAGilRef<T>;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}