Make getters, setters, and constructors compiler errors for enums

.github/workflows/main.yml

@@ -29,7 +29,7 @@ jobs:
     - run: rustup update --no-self-update stable && rustup default stable
     - run: rustup component add rustfmt
     - run: cargo fmt --all -- --check
-  
+
   # Check TOML style by using Taplo.
   taplo:
     name: Taplo
@@ -325,7 +325,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - run: rustup update --no-self-update 1.76.0 && rustup default 1.76.0
+    - run: rustup update --no-self-update 1.78.0 && rustup default 1.78.0
     - run: cargo test -p wasm-bindgen-macro
     - run: cargo test -p wasm-bindgen-test-macro
 

Cargo.toml

@@ -22,12 +22,20 @@ features = ["serde-serialize"]
 test = false
 
 [features]
-default = ["spans", "std"]
+default = ["spans", "std", "diagnostic"]
 enable-interning = ["std"]
 serde-serialize = ["serde", "serde_json", "std"]
 spans = ["wasm-bindgen-macro/spans"]
 std = ["wasm-bindgen-macro/std", "once_cell/std"]
 
+# Enables the use of Rust's `diagnostic` macro for several traits to provide
+# better error messages when those traits are not implemented.
+#
+# Diagnostic messages are only available since Rust 1.78. Enabling this feature
+# for older compilers will NOT improve error message and will NOT result in a
+# compilation error.
+diagnostic = ["rustversion"]
+
 # Whether or not the `#[wasm_bindgen]` macro is strict and generates an error on
 # all unused attributes
 strict-macro = ["wasm-bindgen-macro/strict-macro"]
@@ -43,6 +51,7 @@ xxx_debug_only_print_generated_code = ["wasm-bindgen-macro/xxx_debug_only_print_
 [dependencies]
 cfg-if = "1.0.0"
 once_cell = { version = "1.12", default-features = false }
+rustversion = { version = "1.0", optional = true }
 serde = { version = "1.0", optional = true }
 serde_json = { version = "1.0", optional = true }
 wasm-bindgen-macro = { path = "crates/macro", version = "=0.2.95", default-features = false }

crates/backend/src/codegen.rs

@@ -226,6 +226,13 @@ impl ToTokens for ast::Struct {
         let wasm_bindgen = &self.wasm_bindgen;
         let maybe_no_coverage = coverage();
         (quote! {
+            #[automatically_derived]
+            impl #wasm_bindgen::__rt::marker::SupportsConstructor for #name {}
+            #[automatically_derived]
+            impl #wasm_bindgen::__rt::marker::SupportsInstanceProperty for #name {}
+            #[automatically_derived]
+            impl #wasm_bindgen::__rt::marker::SupportsStaticProperty for #name {}
+
             #[automatically_derived]
             impl #wasm_bindgen::describe::WasmDescribe for #name {
                 fn describe() {
@@ -783,12 +790,44 @@ 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() {
+            // little helper function to make sure the check points to the
+            // location of the function causing the assert to fail
+            let mut add_check = |token_stream| {
+                checks.push(respan(token_stream, &self.rust_name));
+            };
+
+            match &self.method_kind {
+                ast::MethodKind::Constructor => {
+                    add_check(quote! {
+                        struct CheckSupportsConstructor<T: #wasm_bindgen::__rt::marker::SupportsConstructor>(T);
+                        let _: CheckSupportsConstructor<#class>;
+                    });
+                }
+                ast::MethodKind::Operation(operation) => match operation.kind {
+                    ast::OperationKind::Getter(_) | ast::OperationKind::Setter(_) => {
+                        if operation.is_static {
+                            add_check(quote! {
+                                struct CheckSupportsStaticProperty<T: #wasm_bindgen::__rt::marker::SupportsStaticProperty>(T);
+                                let _: CheckSupportsStaticProperty<#class>;
+                            });
+                        } else {
+                            add_check(quote! {
+                                struct CheckSupportsInstanceProperty<T: #wasm_bindgen::__rt::marker::SupportsInstanceProperty>(T);
+                                let _: CheckSupportsInstanceProperty<#class>;
+                            });
+                        }
+                    }
+                    _ => {}
+                },
+            }
+        }
+
         let maybe_no_coverage = coverage();
 
         (quote! {
@@ -801,7 +840,10 @@ impl TryToTokens for ast::Export {
                 )]
                 #maybe_no_coverage
                 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/async-errors.stderr

@@ -22,7 +22,7 @@ error[E0277]: the trait bound `wasm_bindgen::JsValue: From<BadType>` is not sati
   --> ui-tests/async-errors.rs:35:24
    |
 35 | pub async fn bad3() -> BadType { loop {} }
-   |                        ^^^^^^^ the trait `From<BadType>` is not implemented for `wasm_bindgen::JsValue`
+   |                        ^^^^^^^ the trait `From<BadType>` is not implemented for `wasm_bindgen::JsValue`, which is required by `BadType: IntoJsResult`
    |
    = help: the following other types implement trait `From<T>`:
              <wasm_bindgen::JsValue as From<bool>>

crates/macro/ui-tests/main-debug.stderr

@@ -3,3 +3,11 @@ error: the main function has to be called main
    |
 18 | fn fail() {}
    |    ^^^^
+
+warning: unused variable: `f`
+  --> ui-tests/main-debug.rs:12:19
+   |
+12 |     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+   |                   ^ help: if this is intentional, prefix it with an underscore: `_f`
+   |
+   = note: `#[warn(unused_variables)]` on by default

crates/macro/ui-tests/main-infallible.stderr

@@ -3,3 +3,20 @@ error: the main function has to be called main
    |
 10 | fn fail() {}
    |    ^^^^
+
+warning: unreachable expression
+ --> ui-tests/main-infallible.rs:4:1
+  |
+4 | #[wasm_bindgen(main)]
+  | ^^^^^^^^^^^^^^^^^^^^^
+  | |
+  | unreachable expression
+  | any code following this expression is unreachable
+  |
+note: this expression has type `Infallible`, which is uninhabited
+ --> ui-tests/main-infallible.rs:4:1
+  |
+4 | #[wasm_bindgen(main)]
+  | ^^^^^^^^^^^^^^^^^^^^^
+  = note: `#[warn(unreachable_code)]` on by default
+  = note: this warning originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)

crates/macro/ui-tests/missing-catch.stderr

@@ -18,3 +18,38 @@ error[E0277]: the trait bound `Result<wasm_bindgen::JsValue, wasm_bindgen::JsVal
             i128
           and $N others
   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `Result<wasm_bindgen::JsValue, wasm_bindgen::JsValue>: FromWasmAbi` is not satisfied
+ --> ui-tests/missing-catch.rs:3:1
+  |
+3 | #[wasm_bindgen]
+  | ^^^^^^^^^^^^^^^ the trait `FromWasmAbi` is not implemented for `Result<wasm_bindgen::JsValue, wasm_bindgen::JsValue>`
+  |
+  = help: the following other types implement trait `FromWasmAbi`:
+            bool
+            char
+            isize
+            i8
+            i16
+            i32
+            i64
+            i128
+          and $N others
+  = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `Result<wasm_bindgen::JsValue, wasm_bindgen::JsValue>: FromWasmAbi` is not satisfied
+ --> ui-tests/missing-catch.rs:6:18
+  |
+6 |     pub fn foo() -> Result<JsValue, JsValue>;
+  |                     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `FromWasmAbi` is not implemented for `Result<wasm_bindgen::JsValue, wasm_bindgen::JsValue>`
+  |
+  = help: the following other types implement trait `FromWasmAbi`:
+            bool
+            char
+            isize
+            i8
+            i16
+            i32
+            i64
+            i128
+          and $N others

crates/macro/ui-tests/traits-not-implemented.stderr

@@ -15,3 +15,41 @@ error[E0277]: the trait bound `A: IntoWasmAbi` is not satisfied
             i128
           and $N others
   = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `A: IntoWasmAbi` is not satisfied
+ --> ui-tests/traits-not-implemented.rs:8:19
+  |
+8 |     pub fn foo(a: A);
+  |                   ^ the trait `IntoWasmAbi` is not implemented for `A`
+  |
+  = help: the following other types implement trait `IntoWasmAbi`:
+            bool
+            char
+            isize
+            i8
+            i16
+            i32
+            i64
+            i128
+          and $N others
+
+error[E0277]: the trait bound `A: IntoWasmAbi` is not satisfied
+ --> ui-tests/traits-not-implemented.rs:8:12
+  |
+5 | #[wasm_bindgen]
+  | --------------- in this procedural macro expansion
+...
+8 |     pub fn foo(a: A);
+  |            ^^^ the trait `IntoWasmAbi` is not implemented for `A`
+  |
+  = help: the following other types implement trait `IntoWasmAbi`:
+            bool
+            char
+            isize
+            i8
+            i16
+            i32
+            i64
+            i128
+          and $N others
+  = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)

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() {}