Remove warnings from mutable function arguments

soroban-sdk-macros/src/syn_ext.rs

@@ -10,7 +10,7 @@ use syn::{
 };
 use syn::{
     spanned::Spanned, token::And, Error, FnArg, Ident, ImplItem, ImplItemFn, ItemImpl, ItemTrait,
-    Lifetime, Pat, PatType, TraitItem, TraitItemFn, Type, TypeReference, Visibility,
+    Lifetime, Pat, PatIdent, PatType, TraitItem, TraitItemFn, Type, TypeReference, Visibility,
 };
 
 /// Gets methods from the implementation that have public visibility. For
@@ -48,6 +48,26 @@ pub fn fn_arg_ident(arg: &FnArg) -> Result<Ident, Error> {
     ))
 }
 
+/// Modifies a Pat removing any 'mut' on an Ident.
+pub fn pat_unwrap_mut(p: Pat) -> Pat {
+    match p {
+        Pat::Ident(PatIdent {
+            attrs,
+            by_ref,
+            mutability: Some(_),
+            ident,
+            subpat,
+        }) => Pat::Ident(PatIdent {
+            attrs,
+            by_ref,
+            mutability: None,
+            ident,
+            subpat,
+        }),
+        _ => p,
+    }
+}
+
 /// Returns a clone of the type from the FnArg.
 pub fn fn_arg_ref_type(arg: &FnArg, lifetime: Option<&Lifetime>) -> Result<Type, Error> {
     if let FnArg::Typed(pat_type) = arg {
@@ -70,13 +90,13 @@ pub fn fn_arg_ref_type(arg: &FnArg, lifetime: Option<&Lifetime>) -> Result<Type,
 }
 
 /// Returns a clone of FnArg with the type as a reference if the arg is a typed
-/// arg and its type is not already a reference.
+/// arg and its type is not already a reference. Mutability from the ident is stripped.
 pub fn fn_arg_make_ref(arg: &FnArg, lifetime: Option<&Lifetime>) -> FnArg {
     if let FnArg::Typed(pat_type) = arg {
         if !matches!(*pat_type.ty, Type::Reference(_)) {
             return FnArg::Typed(PatType {
                 attrs: pat_type.attrs.clone(),
-                pat: pat_type.pat.clone(),
+                pat: Box::new(pat_unwrap_mut(*pat_type.pat.clone())),
                 colon_token: pat_type.colon_token,
                 ty: Box::new(Type::Reference(TypeReference {
                     and_token: And::default(),
@@ -90,12 +110,14 @@ pub fn fn_arg_make_ref(arg: &FnArg, lifetime: Option<&Lifetime>) -> FnArg {
     arg.clone()
 }
 
+/// Returns a clone of FnArg with the type as an Into if the arg is a typed
+/// arg. Mutability from the ident is stripped.
 pub fn fn_arg_make_into(arg: &FnArg) -> FnArg {
     if let FnArg::Typed(pat_type) = arg {
         let ty = &pat_type.ty;
         return FnArg::Typed(PatType {
             attrs: pat_type.attrs.clone(),
-            pat: pat_type.pat.clone(),
+            pat: Box::new(pat_unwrap_mut(*pat_type.pat.clone())),
             colon_token: pat_type.colon_token,
             ty: Box::new(syn::parse_quote! { impl Into<#ty> }),
         });

soroban-sdk/src/tests/contract_fn.rs

@@ -17,6 +17,11 @@ impl Contract {
     pub fn add_with_unused_arg(_e: &Env, a: i32, _b: i32) -> i32 {
         a + 2
     }
+
+    pub fn add_with_mut_arg(_e: &Env, a: i32, mut b: i32) -> i32 {
+        b *= 1;
+        a + b
+    }
 }
 
 #[contract]
@@ -38,6 +43,9 @@ fn test_functional() {
     let b = 12i32;
     let c = ContractClient::new(&e, &contract_id).add(&a, &b);
     assert_eq!(c, 22);
+
+    let c = ContractClient::new(&e, &contract_id).add_with_mut_arg(&a, &b);
+    assert_eq!(c, 22);
 }
 
 #[test]

soroban-sdk/test_snapshots/tests/contract_fn/test_functional.1.json

@@ -5,6 +5,7 @@
     "mux_id": 0
   },
   "auth": [
+    [],
     [],
     []
   ],