Fix ambiguous associated type error when enum has variant called Error (#3678)

* add test enum with Error variant

* add codegen to resolve enum compilation error

* add test coverage for EnumWithErrorVariant

Author: mlwilkerson

crates/backend/src/codegen.rs

@@ -1456,7 +1456,7 @@ impl ToTokens for ast::Enum {
                 type Error = #wasm_bindgen::JsValue;
 
                 fn try_from(value: #wasm_bindgen::JsValue)
-                    -> #wasm_bindgen::__rt::std::result::Result<Self, Self::Error> {
+                    -> #wasm_bindgen::__rt::std::result::Result<Self, <#enum_name as #wasm_bindgen::__rt::core::convert::TryFrom<JsValue>>::Error> {
                     let js = f64::try_from(&value)? as u32;
 
                     #wasm_bindgen::__rt::std::result::Result::Ok(

tests/wasm/enums.js

@@ -38,3 +38,7 @@ exports.js_expect_enum_none = a => {
 exports.js_renamed_enum = b => {
   assert.strictEqual(wasm.JsRenamedEnum.B, b);
 };
+
+exports.js_enum_with_error_variant = () => {
+    assert.strictEqual(wasm.EnumWithErrorVariant.Error, 2);
+};

tests/wasm/enums.rs

@@ -10,6 +10,7 @@ extern "C" {
     fn js_expect_enum(x: Color, y: Option<Color>);
     fn js_expect_enum_none(x: Option<Color>);
     fn js_renamed_enum(b: RenamedEnum);
+    fn js_enum_with_error_variant();
 }
 
 #[wasm_bindgen]
@@ -71,6 +72,14 @@ pub fn handle_optional_enums(x: Option<Color>) -> Option<Color> {
     x
 }
 
+#[wasm_bindgen]
+#[derive(Copy, Clone)]
+pub enum EnumWithErrorVariant {
+    OK,
+    Warning,
+    Error,
+}
+
 #[wasm_bindgen_test]
 fn test_optional_enums() {
     use self::Color::*;
@@ -95,3 +104,8 @@ fn test_optional_enum_values() {
 fn test_renamed_enum() {
     js_renamed_enum(RenamedEnum::B);
 }
+
+#[wasm_bindgen_test]
+fn test_enum_with_error_variant() {
+    js_enum_with_error_variant();
+}