Make getters, setters, and constructors compiler errors for enums

crates/backend/src/codegen.rs

@@ -224,6 +224,13 @@ impl ToTokens for ast::Struct {
         let unwrap_fn = Ident::new(&shared::unwrap_function(&name_str), Span::call_site());
         let wasm_bindgen = &self.wasm_bindgen;
         (quote! {
+            #[automatically_derived]
+            impl #wasm_bindgen::marker::SupportsConstructor for #name {}
+            #[automatically_derived]
+            impl #wasm_bindgen::marker::SupportsInstanceProperty for #name {}
+            #[automatically_derived]
+            impl #wasm_bindgen::marker::SupportsStaticProperty for #name {}
+
             #[automatically_derived]
             impl #wasm_bindgen::describe::WasmDescribe for #name {
                 fn describe() {
@@ -780,12 +787,43 @@ impl TryToTokens for ast::Export {
         let nargs = self.function.arguments.len() as u32;
         let attrs = &self.function.rust_attrs;
 
-        let start_check = if self.start {
-            quote! { const _ASSERT: fn() = || -> #projection::Abi { loop {} }; }
-        } else {
-            quote! {}
+        let mut checks = Vec::new();
+        if self.start {
+            checks.push(quote! { const _ASSERT: fn() = || -> #projection::Abi { loop {} }; });
         };
 
+        if let Some(class) = self.rust_class.as_ref() {
+            // change span of class, so it points to the location of the
+            // function causing the assert to fail
+            let mut class = class.clone();
+            class.set_span(self.rust_name.span());
+
+            match &self.method_kind {
+                ast::MethodKind::Constructor => {
+                    checks.push(quote! {
+                        const fn assert_supports_constructor<T: #wasm_bindgen::marker::SupportsConstructor>() {}
+                        assert_supports_constructor::<#class>();
+                    });
+                }
+                ast::MethodKind::Operation(operation) => match operation.kind {
+                    ast::OperationKind::Getter(_) | ast::OperationKind::Setter(_) => {
+                        if operation.is_static {
+                            checks.push(quote! {
+                                    const fn assert_supports_static_property<T: #wasm_bindgen::marker::SupportsStaticProperty>() {}
+                                    assert_supports_static_property::<#class>();
+                                });
+                        } else {
+                            checks.push(quote! {
+                                    const fn assert_supports_instance_property<T: #wasm_bindgen::marker::SupportsInstanceProperty>() {}
+                                    assert_supports_instance_property::<#class>();
+                                });
+                        }
+                    }
+                    _ => {}
+                },
+            }
+        }
+
         (quote! {
             #[automatically_derived]
             const _: () = {
@@ -796,7 +834,10 @@ impl TryToTokens for ast::Export {
                 )]
                 #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 pub unsafe extern "C" fn #generated_name(#(#args),*) -> #wasm_bindgen::convert::WasmRet<#projection::Abi> {
-                    #start_check
+                    #[automatically_derived]
+                    const _: () = {
+                        #(#checks)*
+                    };
 
                     let #ret = #call;
                     #convert_ret

crates/macro/ui-tests/unsupported-options.rs

@@ -0,0 +1,82 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+pub struct RustStruct {
+    data: u32,
+}
+
+#[wasm_bindgen]
+impl RustStruct {
+    pub fn instance_method(&self) {}
+    fn priv_instance_method(&self) {}
+    pub fn static_method() {}
+
+    #[wasm_bindgen(constructor)]
+    pub fn new() -> Self {
+        Self { data: 0 }
+    }
+
+    #[wasm_bindgen(getter)]
+    pub fn prop(self) -> u32 {
+        32
+    }
+    #[wasm_bindgen(setter)]
+    pub fn set_prop(self, _value: u32) {}
+
+    #[wasm_bindgen(getter)]
+    pub fn static_prop() -> u32 {
+        32
+    }
+    #[wasm_bindgen(setter)]
+    pub fn set_static_prop(_value: u32) {}
+
+    #[wasm_bindgen(indexing_getter)]
+    pub fn indexing_getter(self) -> u32 {
+        32
+    }
+    #[wasm_bindgen(indexing_setter)]
+    pub fn indexing_setter(self, _value: u32) {}
+    #[wasm_bindgen(indexing_deleter)]
+    pub fn indexing_deleter(self, _value: u32) {}
+}
+
+#[wasm_bindgen]
+pub enum RustEnum {
+    A = 0,
+    B = 1,
+}
+
+#[wasm_bindgen]
+impl RustEnum {
+    pub fn instance_method(self) {}
+    fn priv_instance_method(self) {}
+    pub fn static_method() {}
+
+    #[wasm_bindgen(constructor)]
+    pub fn new() -> Self {
+        Self::A
+    }
+
+    #[wasm_bindgen(getter)]
+    pub fn prop(self) -> u32 {
+        32
+    }
+    #[wasm_bindgen(setter)]
+    pub fn set_prop(self, _value: u32) {}
+
+    #[wasm_bindgen(getter)]
+    pub fn static_prop() -> u32 {
+        32
+    }
+    #[wasm_bindgen(setter)]
+    pub fn set_static_prop(_value: u32) {}
+}
+
+pub struct NonWasmType;
+
+#[wasm_bindgen]
+impl NonWasmType {
+    pub fn static_method() {}
+}
+
+fn main() {}

crates/macro/ui-tests/unsupported-options.stderr

@@ -0,0 +1,80 @@
+error[E0277]: JavaScript constructors are not supported for `RustEnum`
+  --> ui-tests/unsupported-options.rs:56:12
+   |
+56 |     pub fn new() -> Self {
+   |            ^^^ this function cannot be the constructor of `RustEnum`
+   |
+   = help: the trait `SupportsConstructor` is not implemented for `RustEnum`
+   = note: `#[wasm_bindgen(constructor)]` is generally only supported for `struct`s with `#[wasm_bindgen]` and cannot be used for `enum`s.
+   = note: Consider removing the `constructor` option and using a regular static method instead.
+   = help: the trait `SupportsConstructor` is implemented for `RustStruct`
+note: required by a bound in `__wasm_bindgen_generated_RustEnum_new::_::assert_supports_constructor`
+  --> ui-tests/unsupported-options.rs:49:1
+   |
+49 | #[wasm_bindgen]
+   | ^^^^^^^^^^^^^^^ required by this bound in `assert_supports_constructor`
+   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: JavaScript instance getters and setters are not supported for `RustEnum`
+  --> ui-tests/unsupported-options.rs:61:12
+   |
+61 |     pub fn prop(self) -> u32 {
+   |            ^^^^ this method cannot be a getter or setter for `RustEnum`
+   |
+   = help: the trait `SupportsInstanceProperty` is not implemented for `RustEnum`
+   = note: `#[wasm_bindgen(getter)]` and `#[wasm_bindgen(setter)]` are generally only supported for `struct`s with `#[wasm_bindgen]`. They cannot be used for `enum`s.
+   = help: the trait `SupportsInstanceProperty` is implemented for `RustStruct`
+note: required by a bound in `__wasm_bindgen_generated_RustEnum_prop::_::assert_supports_instance_property`
+  --> ui-tests/unsupported-options.rs:49:1
+   |
+49 | #[wasm_bindgen]
+   | ^^^^^^^^^^^^^^^ required by this bound in `assert_supports_instance_property`
+   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: JavaScript instance getters and setters are not supported for `RustEnum`
+  --> ui-tests/unsupported-options.rs:65:12
+   |
+65 |     pub fn set_prop(self, _value: u32) {}
+   |            ^^^^^^^^ this method cannot be a getter or setter for `RustEnum`
+   |
+   = help: the trait `SupportsInstanceProperty` is not implemented for `RustEnum`
+   = note: `#[wasm_bindgen(getter)]` and `#[wasm_bindgen(setter)]` are generally only supported for `struct`s with `#[wasm_bindgen]`. They cannot be used for `enum`s.
+   = help: the trait `SupportsInstanceProperty` is implemented for `RustStruct`
+note: required by a bound in `__wasm_bindgen_generated_RustEnum_set_prop::_::assert_supports_instance_property`
+  --> ui-tests/unsupported-options.rs:49:1
+   |
+49 | #[wasm_bindgen]
+   | ^^^^^^^^^^^^^^^ required by this bound in `assert_supports_instance_property`
+   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: JavaScript static getters and setters are not supported for `RustEnum`
+  --> ui-tests/unsupported-options.rs:68:12
+   |
+68 |     pub fn static_prop() -> u32 {
+   |            ^^^^^^^^^^^ this static function cannot be a static getter or setter on `RustEnum`
+   |
+   = help: the trait `SupportsStaticProperty` is not implemented for `RustEnum`
+   = note: `#[wasm_bindgen(getter)]` and `#[wasm_bindgen(setter)]` are generally only supported for `struct`s with `#[wasm_bindgen]`. They cannot be used for `enum`s.
+   = help: the trait `SupportsStaticProperty` is implemented for `RustStruct`
+note: required by a bound in `__wasm_bindgen_generated_RustEnum_static_prop::_::assert_supports_static_property`
+  --> ui-tests/unsupported-options.rs:49:1
+   |
+49 | #[wasm_bindgen]
+   | ^^^^^^^^^^^^^^^ required by this bound in `assert_supports_static_property`
+   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: JavaScript static getters and setters are not supported for `RustEnum`
+  --> ui-tests/unsupported-options.rs:72:12
+   |
+72 |     pub fn set_static_prop(_value: u32) {}
+   |            ^^^^^^^^^^^^^^^ this static function cannot be a static getter or setter on `RustEnum`
+   |
+   = help: the trait `SupportsStaticProperty` is not implemented for `RustEnum`
+   = note: `#[wasm_bindgen(getter)]` and `#[wasm_bindgen(setter)]` are generally only supported for `struct`s with `#[wasm_bindgen]`. They cannot be used for `enum`s.
+   = help: the trait `SupportsStaticProperty` is implemented for `RustStruct`
+note: required by a bound in `__wasm_bindgen_generated_RustEnum_set_static_prop::_::assert_supports_static_property`
+  --> ui-tests/unsupported-options.rs:49:1
+   |
+49 | #[wasm_bindgen]
+   | ^^^^^^^^^^^^^^^ required by this bound in `assert_supports_static_property`
+   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)

src/lib.rs

@@ -16,7 +16,7 @@ use alloc::boxed::Box;
 use alloc::string::String;
 use alloc::vec::Vec;
 use core::convert::TryFrom;
-use core::marker;
+use core::marker::PhantomData;
 use core::mem;
 use core::ops::{
     Add, BitAnd, BitOr, BitXor, Deref, DerefMut, Div, Mul, Neg, Not, Rem, Shl, Shr, Sub,
@@ -71,6 +71,7 @@ pub use wasm_bindgen_macro::link_to;
 pub mod closure;
 pub mod convert;
 pub mod describe;
+pub mod marker;
 mod link;
 
 mod cast;
@@ -92,7 +93,7 @@ if_std! {
 /// but for now it may be slightly slow.
 pub struct JsValue {
     idx: u32,
-    _marker: marker::PhantomData<*mut u8>, // not at all threadsafe
+    _marker: PhantomData<*mut u8>, // not at all threadsafe
 }
 
 const JSIDX_OFFSET: u32 = 128; // keep in sync with js/mod.rs
@@ -119,7 +120,7 @@ impl JsValue {
     const fn _new(idx: u32) -> JsValue {
         JsValue {
             idx,
-            _marker: marker::PhantomData,
+            _marker: PhantomData,
         }
     }
 

src/marker.rs

@@ -0,0 +1,61 @@
+//! This module contains marker traits used by `wasm-bindgen` to verify its
+//! generated code.
+//!
+//! # ⚠️ Unstable
+//!
+//! This is an internal module, no stability guarantees are provided. Use at
+//! your own risk.
+
+/// Marker trait for types that support `#[wasm_bindgen(constructor)]`.
+///
+/// **DO NOT** implement this trait manually. It is implemented automatically
+/// for types that support constructors.
+///
+/// # ⚠️ Unstable
+///
+/// This is part of the internal [`convert`](crate::marker) module, **no
+/// stability guarantees** are provided. Use at your own risk. See its
+/// documentation for more details.
+#[diagnostic::on_unimplemented(
+    message = "JavaScript constructors are not supported for `{Self}`",
+    label = "this function cannot be the constructor of `{Self}`",
+    note = "`#[wasm_bindgen(constructor)]` is generally only supported for `struct`s with `#[wasm_bindgen]` and cannot be used for `enum`s.",
+    note = "Consider removing the `constructor` option and using a regular static method instead."
+)]
+pub trait SupportsConstructor {}
+
+/// Marker trait for types that support `#[wasm_bindgen(getter)]` or
+/// `#[wasm_bindgen(Setter)]` on instance methods.
+///
+/// **DO NOT** implement this trait manually. It is implemented automatically
+/// for types that support instance properties.
+///
+/// # ⚠️ Unstable
+///
+/// This is part of the internal [`convert`](crate::marker) module, **no
+/// stability guarantees** are provided. Use at your own risk. See its
+/// documentation for more details.
+#[diagnostic::on_unimplemented(
+    message = "JavaScript instance getters and setters are not supported for `{Self}`",
+    label = "this method cannot be a getter or setter for `{Self}`",
+    note = "`#[wasm_bindgen(getter)]` and `#[wasm_bindgen(setter)]` are generally only supported for `struct`s with `#[wasm_bindgen]`. They cannot be used for `enum`s."
+)]
+pub trait SupportsInstanceProperty {}
+
+/// Marker trait for types that support `#[wasm_bindgen(getter)]` or
+/// `#[wasm_bindgen(Setter)]` on static methods.
+///
+/// **DO NOT** implement this trait manually. It is implemented automatically
+/// for types that support static properties.
+///
+/// # ⚠️ Unstable
+///
+/// This is part of the internal [`convert`](crate::marker) module, **no
+/// stability guarantees** are provided. Use at your own risk. See its
+/// documentation for more details.
+#[diagnostic::on_unimplemented(
+    message = "JavaScript static getters and setters are not supported for `{Self}`",
+    label = "this static function cannot be a static getter or setter on `{Self}`",
+    note = "`#[wasm_bindgen(getter)]` and `#[wasm_bindgen(setter)]` are generally only supported for `struct`s with `#[wasm_bindgen]`. They cannot be used for `enum`s."
+)]
+pub trait SupportsStaticProperty {}