Properly handle mutability for awaited futures

rstest_macros/src/refident.rs

@@ -1,7 +1,7 @@
 /// Provide `RefIdent` and `MaybeIdent` traits that give a shortcut to extract identity reference
 /// (`syn::Ident` struct).
 use proc_macro2::Ident;
-use syn::{FnArg, Pat, PatType, Type};
+use syn::{FnArg, Pat, PatType, Token, Type};
 
 pub trait RefIdent {
     /// Return the reference to ident if any
@@ -86,3 +86,35 @@ impl MaybeIdent for crate::parse::Attribute {
         }
     }
 }
+
+pub trait MaybeMutability {
+    fn maybe_mutability(&self) -> Option<Token![mut]>;
+}
+
+impl MaybeMutability for FnArg {
+    fn maybe_mutability(&self) -> Option<Token![mut]> {
+        match self {
+            FnArg::Typed(PatType { pat, .. }) => match pat.as_ref() {
+                Pat::Ident(ident) => ident.mutability,
+                _ => None,
+            },
+            _ => None,
+        }
+    }
+}
+
+pub trait SetMutability {
+    fn set_mutability(&mut self, mutability: Option<Token![mut]>);
+}
+
+impl SetMutability for FnArg {
+    fn set_mutability(&mut self, mutability: Option<Token![mut]>) {
+        match self {
+            FnArg::Typed(PatType { pat, .. }) => match pat.as_mut() {
+                Pat::Ident(ident) => ident.mutability = mutability,
+                _ => {}
+            },
+            _ => {}
+        };
+    }
+}

rstest_macros/src/render/apply_argumets.rs

@@ -3,7 +3,7 @@ use syn::{parse_quote, FnArg, Generics, Ident, ItemFn, Lifetime, Signature, Type
 
 use crate::{
     parse::{arguments::ArgumentsInfo, future::MaybeFutureImplType},
-    refident::MaybeIdent,
+    refident::{MaybeIdent, MaybeMutability, SetMutability},
 };
 
 pub(crate) trait ApplyArgumets<R: Sized = ()> {
@@ -63,13 +63,13 @@ impl ApplyArgumets for ItemFn {
             .sig
             .inputs
             .iter()
-            .filter_map(|a| a.maybe_ident())
-            .filter(|&a| arguments.is_future_await(a))
-            .cloned();
+            .filter_map(|a| a.maybe_ident().map(|i| (i, a.maybe_mutability())))
+            .filter(|(a, _)| arguments.is_future_await(a))
+            .map(|(a, m)| quote::quote! { let #m #a = #a.await; });
         let orig_block_impl = self.block.clone();
         self.block = parse_quote! {
             {
-                #(let #awaited_args = #awaited_args.await;)*
+                #(#awaited_args)*
                 #orig_block_impl
             }
         };
@@ -90,6 +90,7 @@ impl ImplFutureArg for FnArg {
                 *ty = parse_quote! {
                     impl std::future::Future<Output = #ty>
                 };
+                self.set_mutability(None);
                 lifetime
             }
             None => None,