Remove span in generated field getter (#3725)

Author: Liamolucko

CHANGELOG.md

@@ -8,6 +8,11 @@
 * Add bindings for `UserActivation`.
   [#3719](https://github.com/rustwasm/wasm-bindgen/pull/3719)
 
+### Fixed
+
+* Fixed a compiler error when using `#[wasm_bindgen]` inside `macro_rules!`.
+  [#3725](https://github.com/rustwasm/wasm-bindgen/pull/3725)
+
 ### Removed
 
 * Removed Gecko-only `InstallTriggerData` and Gecko-internal `FlexLineGrowthState`, `GridDeclaration`, `GridTrackState`,

crates/backend/src/codegen.rs

@@ -389,7 +389,14 @@ impl ToTokens for ast::StructField {
         };
         let maybe_assert_copy = respan(maybe_assert_copy, ty);
 
-        let mut val = quote_spanned!(self.rust_name.span()=> (*js).borrow().#rust_name);
+        // Split this out so that it isn't affected by `quote_spanned!`.
+        //
+        // If we don't do this, it might end up being unable to reference `js`
+        // properly because it doesn't have the same span.
+        //
+        // See https://github.com/rustwasm/wasm-bindgen/pull/3725.
+        let js_token = quote! { js };
+        let mut val = quote_spanned!(self.rust_name.span()=> (*#js_token).borrow().#rust_name);
         if let Some(span) = self.getter_with_clone {
             val = quote_spanned!(span=> <#ty as Clone>::clone(&#val) );
         }

tests/wasm/classes.js

@@ -241,3 +241,10 @@ exports.js_test_inspectable_classes_can_override_generated_methods = () => {
     assert.strictEqual(overridden_inspectable.toString(), 'string was overwritten');
     overridden_inspectable.free();
 };
+
+exports.js_test_class_defined_in_macro = () => {
+    const macroClass = new wasm.InsideMacro();
+    assert.strictEqual(macroClass.a, 3);
+    macroClass.a = 5;
+    assert.strictEqual(macroClass.a, 5);
+};

tests/wasm/classes.rs

@@ -34,6 +34,7 @@ extern "C" {
     fn js_test_option_classes();
     fn js_test_inspectable_classes();
     fn js_test_inspectable_classes_can_override_generated_methods();
+    fn js_test_class_defined_in_macro();
 }
 
 #[wasm_bindgen_test]
@@ -608,3 +609,27 @@ impl OverriddenInspectable {
         String::from("string was overwritten")
     }
 }
+
+macro_rules! make_struct {
+    ($field:ident) => {
+        #[wasm_bindgen]
+        pub struct InsideMacro {
+            pub $field: u32,
+        }
+    };
+}
+
+make_struct!(a);
+
+#[wasm_bindgen]
+impl InsideMacro {
+    #[wasm_bindgen(constructor)]
+    pub fn new() -> Self {
+        Self { a: 3 }
+    }
+}
+
+#[wasm_bindgen_test]
+fn class_defined_in_macro() {
+    js_test_class_defined_in_macro();
+}