Add enum types for function parameters and return types

CHANGELOG.md

@@ -104,6 +104,10 @@
   as normal exceptions rather than as rejected promises.
   [#3611](https://github.com/rustwasm/wasm-bindgen/pull/3611)
 
+* Improved TypeScript bindings to accurately reference Rust enum types in function signatures,
+  enhancing type safety and compatibility.
+  [#3647](https://github.com/rustwasm/wasm-bindgen/pull/3647)
+
 ### Fixed
 
 * Fixed `wasm_bindgen` macro to handle raw identifiers in field names.

crates/backend/src/codegen.rs

@@ -1382,6 +1382,9 @@ impl<'a> ToTokens for DescribeImport<'a> {
 impl ToTokens for ast::Enum {
     fn to_tokens(&self, into: &mut TokenStream) {
         let enum_name = &self.rust_name;
+        let name_str = self.js_name.to_string();
+        let name_len = name_str.len() as u32;
+        let name_chars = name_str.chars().map(|c| c as u32);
         let hole = &self.hole;
         let cast_clauses = self.variants.iter().map(|variant| {
             let variant_name = &variant.name;
@@ -1433,6 +1436,8 @@ impl ToTokens for ast::Enum {
                 fn describe() {
                     use #wasm_bindgen::describe::*;
                     inform(ENUM);
+                    inform(#name_len);
+                    #(inform(#name_chars);)*
                     inform(#hole);
                 }
             }

crates/cli-support/src/descriptor.rs

@@ -66,7 +66,7 @@ pub enum Descriptor {
     String,
     Externref,
     NamedExternref(String),
-    Enum { hole: u32 },
+    Enum { name: String, hole: u32 },
     RustStruct(String),
     Char,
     Option(Box<Descriptor>),
@@ -149,7 +149,11 @@ impl Descriptor {
             CACHED_STRING => Descriptor::CachedString,
             STRING => Descriptor::String,
             EXTERNREF => Descriptor::Externref,
-            ENUM => Descriptor::Enum { hole: get(data) },
+            ENUM => {
+                let name = get_string(data);
+                let hole = get(data);
+                Descriptor::Enum { name, hole }
+            }
             RUST_STRUCT => {
                 let name = get_string(data);
                 Descriptor::RustStruct(name)

crates/cli-support/src/js/binding.rs

@@ -1336,6 +1336,7 @@ fn adapter2ts(ty: &AdapterType, dst: &mut String) {
         }
         AdapterType::NamedExternref(name) => dst.push_str(name),
         AdapterType::Struct(name) => dst.push_str(name),
+        AdapterType::Enum(name) => dst.push_str(name),
         AdapterType::Function => dst.push_str("any"),
     }
 }

crates/cli-support/src/wit/incoming.rs

@@ -98,7 +98,16 @@ impl InstructionBuilder<'_, '_> {
                 self.get(AdapterType::F64);
                 self.output.push(AdapterType::F64);
             }
-            Descriptor::Enum { .. } => self.number(AdapterType::U32, WasmVT::I32),
+            Descriptor::Enum { name, .. } => {
+                self.instruction(
+                    &[AdapterType::Enum(name.clone())],
+                    Instruction::IntToWasm {
+                        input: AdapterType::U32,
+                        output: ValType::I32,
+                    },
+                    &[AdapterType::I32],
+                );
+            },
             Descriptor::Ref(d) => self.incoming_ref(false, d)?,
             Descriptor::RefMut(d) => self.incoming_ref(true, d)?,
             Descriptor::Option(d) => self.incoming_option(d)?,
@@ -274,9 +283,9 @@ impl InstructionBuilder<'_, '_> {
                     &[AdapterType::I32],
                 );
             }
-            Descriptor::Enum { hole } => {
+            Descriptor::Enum { name, hole } => {
                 self.instruction(
-                    &[AdapterType::U32.option()],
+                    &[AdapterType::Enum(name.clone()).option()],
                     Instruction::I32FromOptionEnum { hole: *hole },
                     &[AdapterType::I32],
                 );

crates/cli-support/src/wit/outgoing.rs

@@ -73,7 +73,7 @@ impl InstructionBuilder<'_, '_> {
                 self.get(AdapterType::F64);
                 self.output.push(AdapterType::F64);
             }
-            Descriptor::Enum { .. } => self.outgoing_i32(AdapterType::U32),
+            Descriptor::Enum { name, .. } => self.outgoing_i32(AdapterType::Enum(name.clone())),
 
             Descriptor::Char => {
                 self.instruction(
@@ -278,11 +278,11 @@ impl InstructionBuilder<'_, '_> {
                     &[AdapterType::String.option()],
                 );
             }
-            Descriptor::Enum { hole } => {
+            Descriptor::Enum { name, hole } => {
                 self.instruction(
                     &[AdapterType::I32],
                     Instruction::OptionEnumFromI32 { hole: *hole },
-                    &[AdapterType::U32.option()],
+                    &[AdapterType::Enum(name.clone()).option()],
                 );
             }
             Descriptor::RustStruct(name) => {

crates/cli-support/src/wit/standard.rs

@@ -85,6 +85,7 @@ pub enum AdapterType {
     Vector(VectorKind),
     Option(Box<AdapterType>),
     Struct(String),
+    Enum(String),
     NamedExternref(String),
     Function,
 }
@@ -327,6 +328,7 @@ impl AdapterType {
             AdapterType::I64 => walrus::ValType::I64,
             AdapterType::F32 => walrus::ValType::F32,
             AdapterType::F64 => walrus::ValType::F64,
+            AdapterType::Enum(_) => walrus::ValType::I32,
             AdapterType::Externref | AdapterType::NamedExternref(_) => walrus::ValType::Externref,
             _ => return None,
         })

crates/typescript-tests/src/enums.rs

@@ -5,3 +5,19 @@ pub enum Foo {
     A = 1,
     B = 3,
 }
+
+#[wasm_bindgen]
+pub fn fn_expects_enum(_: Foo) {}
+
+#[wasm_bindgen]
+pub fn fn_returns_enum() -> Foo {
+    Foo::A
+}
+
+#[wasm_bindgen]
+pub fn fn_expects_option_enum(_: Option<Foo>) {}
+
+#[wasm_bindgen]
+pub fn fn_returns_option_enum() -> Option<Foo> {
+    Some(Foo::A)
+}

crates/typescript-tests/src/enums.ts

@@ -6,3 +6,8 @@ const a3: wbg.Foo.A = 1;
 const b1: wbg.Foo = wbg.Foo.B;
 const b2: wbg.Foo.B = wbg.Foo.B;
 const b3: wbg.Foo.B = 3;
+
+const fn_expects_enum: (_: wbg.Foo) => void = wbg.fn_expects_enum;
+const fn_returns_enum: () => wbg.Foo = wbg.fn_returns_enum;
+const fn_expects_option_enum: (_?: wbg.Foo) => void = wbg.fn_expects_option_enum;
+const fn_returns_option_enum: () => wbg.Foo | undefined = wbg.fn_returns_option_enum;