From b64aadb8a9702ea92bac2c086c9b2fe39cb96031 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20R=C3=B6nnkvist?= <daniel@ronnkvist.com>
Date: Mon, 13 Jan 2025 10:34:49 +0100
Subject: [PATCH] Move deprecation warning to function definition

Update tests to work with the new deprecation
---
 crates/backend/src/codegen.rs                    | 10 ++++++++++
 crates/macro-support/src/parser.rs               |  5 -----
 crates/macro/ui-tests/unsupported-options.stderr | 16 ++++++++--------
 tests/wasm/futures.js                            |  2 +-
 tests/wasm/futures.rs                            |  1 -
 5 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/crates/backend/src/codegen.rs b/crates/backend/src/codegen.rs
index c8decb4a136..8ae6b738c00 100644
--- a/crates/backend/src/codegen.rs
+++ b/crates/backend/src/codegen.rs
@@ -806,6 +806,16 @@ impl TryToTokens for ast::Export {
                     add_check(quote! {
                         let _: #wasm_bindgen::__rt::marker::CheckSupportsConstructor<#class>;
                     });
+
+                    if self.function.r#async {
+                        (quote_spanned! {
+                            self.function.name_span =>
+                            #[deprecated(note = "async constructors are not supported")]
+                            fn constructor() {}
+                            constructor();
+                        })
+                        .to_tokens(into);
+                    }
                 }
                 ast::MethodKind::Operation(operation) => match operation.kind {
                     ast::OperationKind::Getter(_) | ast::OperationKind::Setter(_) => {
diff --git a/crates/macro-support/src/parser.rs b/crates/macro-support/src/parser.rs
index a10d823b3b3..46c76a1ef21 100644
--- a/crates/macro-support/src/parser.rs
+++ b/crates/macro-support/src/parser.rs
@@ -1418,11 +1418,6 @@ impl MacroParse<&ClassMarker> for &mut syn::ImplItemFn {
             FunctionPosition::Impl { self_ty: class },
         )?;
         let method_kind = if opts.constructor().is_some() {
-            if function.r#async {
-                self.attrs.push(syn::parse_quote! {
-                    #[deprecated(note = "constructors cannot be async")]
-                });
-            }
             ast::MethodKind::Constructor
         } else {
             let is_static = method_self.is_none();
diff --git a/crates/macro/ui-tests/unsupported-options.stderr b/crates/macro/ui-tests/unsupported-options.stderr
index cecba3a4b18..0ec899efad7 100644
--- a/crates/macro/ui-tests/unsupported-options.stderr
+++ b/crates/macro/ui-tests/unsupported-options.stderr
@@ -1,3 +1,11 @@
+warning: use of deprecated function `RustStruct::new::{closure#0}::constructor`: async constructors are not supported
+  --> ui-tests/unsupported-options.rs:15:18
+   |
+15 |     pub async fn new() -> Self {
+   |                  ^^^
+   |
+   = note: `#[warn(deprecated)]` on by default
+
 error[E0277]: JavaScript constructors are not supported for `RustEnum`
   --> ui-tests/unsupported-options.rs:56:12
    |
@@ -93,11 +101,3 @@ note: required by a bound in `CheckSupportsStaticProperty`
    | pub struct CheckSupportsStaticProperty<T: SupportsStaticProperty>(T);
    |                                           ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `CheckSupportsStaticProperty`
    = note: this error originates in the attribute macro `wasm_bindgen::prelude::__wasm_bindgen_class_marker` which comes from the expansion of the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-warning: use of deprecated associated function `RustStruct::new`: constructors cannot be async
-  --> ui-tests/unsupported-options.rs:84:21
-   |
-84 |         RustStruct::new().await;
-   |                     ^^^
-   |
-   = note: `#[warn(deprecated)]` on by default
diff --git a/tests/wasm/futures.js b/tests/wasm/futures.js
index b9560866071..127beb2f528 100644
--- a/tests/wasm/futures.js
+++ b/tests/wasm/futures.js
@@ -16,7 +16,7 @@ exports.call_exports = async function() {
   await assert.rejects(wasm.async_throw_jserror(), /async message/);
   await assert.rejects(wasm.async_throw_custom_error(), /custom error/);
   assert.strictEqual("Hi, Jim!", await wasm.async_take_reference("Jim"));
-  const foo = await new wasm.AsyncStruct();
+  const foo = await wasm.AsyncStruct.new();
   assert.strictEqual(42, await foo.method());
   await wasm.async_take_js_reference(42);
   const buffer = new Int32Array([1, 2, 3, 4]);
diff --git a/tests/wasm/futures.rs b/tests/wasm/futures.rs
index 73b51dd06d3..c50722e1cad 100644
--- a/tests/wasm/futures.rs
+++ b/tests/wasm/futures.rs
@@ -123,7 +123,6 @@ pub struct AsyncStruct;
 
 #[wasm_bindgen]
 impl AsyncStruct {
-    #[wasm_bindgen(constructor)]
     pub async fn new() -> AsyncStruct {
         AsyncStruct
     }