Unwrap argument types in macro (#3625)

CHANGELOG.md

@@ -129,6 +129,9 @@
   proc-macro.
   [#3601](https://github.com/rustwasm/wasm-bindgen/pull/3601)
 
+* Fix bug with function arguments coming from `macro_rules!`.
+  [#3625](https://github.com/rustwasm/wasm-bindgen/pull/3625)
+
 ### Removed
 
 * Removed `ReadableStreamByobReader::read_with_u8_array()` because it doesn't work with Wasm.

crates/backend/src/codegen.rs

@@ -523,8 +523,16 @@ impl TryToTokens for ast::Export {
             argtys.push(&*arg.ty);
             let i = i + offset;
             let ident = Ident::new(&format!("arg{}", i), Span::call_site());
-            let ty = &arg.ty;
-            match &*arg.ty {
+            fn unwrap_nested_types(ty: &syn::Type) -> &syn::Type {
+                match &ty {
+                    syn::Type::Group(syn::TypeGroup { ref elem, .. }) => unwrap_nested_types(elem),
+                    syn::Type::Paren(syn::TypeParen { ref elem, .. }) => unwrap_nested_types(elem),
+                    _ => ty,
+                }
+            }
+            let ty = unwrap_nested_types(&arg.ty);
+
+            match &ty {
                 syn::Type::Reference(syn::TypeReference {
                     mutability: Some(_),
                     elem,

tests/wasm/macro_rules.rs

@@ -0,0 +1,12 @@
+//! This tests that the `wasm_bindgen` macro produces code that compiles for this use case.
+//! `cargo test --target wasm32-unknown-unknown` will not run if this test breaks.
+use wasm_bindgen::prelude::*;
+
+macro_rules! my_export {
+    ($i: ident, $s: ty) => {
+        #[wasm_bindgen]
+        pub fn $i(_: $s) {}
+    };
+}
+
+my_export!(should_compile, &[i32]);

tests/wasm/main.rs

@@ -35,6 +35,7 @@ pub mod js_keywords;
 pub mod js_objects;
 pub mod jscast;
 pub mod link_to;
+pub mod macro_rules;
 pub mod math;
 pub mod no_shims;
 pub mod node;