Leverage new rustc wasm features

This commit leverages two new attributes in the Rust compiler,
`#[wasm_custom_section]` and `#[wasm_import_module]`. These two attributes allow
removing a lot of hacks found in wasm-bindgen and also allows removing the
requirement of `wasm-opt` to remove the unused data sections.

This does require two new nightly features but we already required the
`proc_macro` nightly feature and these will hopefully be stabilized before that
feature!

README.md

@@ -76,7 +76,7 @@ wasm-bindgen = "0.1"
 Next up our actual code! We'll write this in `src/lib.rs`:
 
 ```rust
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 
@@ -261,7 +261,7 @@ Much more! Here's a taste of various features you can use in this project:
 
 ```rust
 // src/lib.rs
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

crates/wasm-bindgen-cli-support/src/js.rs

@@ -16,7 +16,6 @@ pub struct Context<'a> {
     pub required_internal_exports: HashSet<&'static str>,
     pub config: &'a Bindgen,
     pub module: &'a mut Module,
-    pub imports_to_rewrite: HashSet<String>,
     pub custom_type_names: HashMap<char, String>,
     pub imported_names: HashSet<String>,
     pub exported_classes: HashMap<String, ExportedClass>,
@@ -288,18 +287,7 @@ impl<'a> Context<'a> {
             .flat_map(|s| s.entries_mut());
 
         for import in imports {
-            if import.field().starts_with("__wbindgen") {
-                import.module_mut().truncate(0);
-                import.module_mut().push_str("./");
-                import.module_mut().push_str(module_name);
-                continue
-            }
-
-            // rustc doesn't have support for importing from anything other
-            // than the module `env` so let's use the metadata here to
-            // rewrite the imports if they import from `env` until it's
-            // fixed upstream.
-            if self.imports_to_rewrite.contains(import.field()) {
+            if import.module() == "__wbindgen_placeholder__" {
                 import.module_mut().truncate(0);
                 import.module_mut().push_str("./");
                 import.module_mut().push_str(module_name);
@@ -954,7 +942,7 @@ impl<'a> Context<'a> {
         };
 
         imports.entries().iter().any(|i| {
-            i.module() == "env" && i.field() == name
+            i.module() == "__wbindgen_placeholder__" && i.field() == name
         })
     }
 
@@ -1336,7 +1324,6 @@ impl<'a, 'b> SubContext<'a, 'b> {
                                   info: &shared::Import,
                                   import: &shared::ImportStatic) {
         // TODO: should support more types to import here
-        self.cx.imports_to_rewrite.insert(import.shim.clone());
         let obj = self.import_name(info, &import.name);
         self.cx.expose_add_heap_object();
         self.cx.globals.push_str(&format!("
@@ -1349,8 +1336,6 @@ impl<'a, 'b> SubContext<'a, 'b> {
     pub fn generate_import_function(&mut self,
                                     info: &shared::Import,
                                     import: &shared::ImportFunction) {
-        self.cx.imports_to_rewrite.insert(import.shim.clone());
-
         let mut dst = String::new();
 
         dst.push_str(&format!("function {}(", import.shim));

crates/wasm-bindgen-cli-support/src/lib.rs

@@ -6,7 +6,6 @@ extern crate wasm_gc;
 use std::char;
 use std::fs::File;
 use std::io::Write;
-use std::ops::{Deref, DerefMut};
 use std::path::{Path, PathBuf};
 use std::slice;
 
@@ -90,7 +89,6 @@ impl Bindgen {
                 typescript: format!("/* tslint:disable */\n"),
                 exposed_globals: Default::default(),
                 required_internal_exports: Default::default(),
-                imports_to_rewrite: Default::default(),
                 custom_type_names: Default::default(),
                 imported_names: Default::default(),
                 exported_classes: Default::default(),
@@ -133,40 +131,33 @@ impl Bindgen {
 
 fn extract_programs(module: &mut Module) -> Vec<shared::Program> {
     let version = shared::version();
-    let data = module.sections_mut()
-        .iter_mut()
-        .filter_map(|s| {
-            match *s {
-                Section::Data(ref mut s) => Some(s),
-                _ => None,
-            }
-        })
-        .next();
-
     let mut ret = Vec::new();
-    let data = match data {
-        Some(data) => data,
-        None => return ret,
+
+    #[repr(packed)]
+    struct Unaligned(u32);
+
+    module.sections_mut().retain(|s| {
+        let custom = match *s {
+            Section::Custom(ref s) => s,
+            _ => return true,
+        };
+        if custom.name() != "__wasm_bindgen_unstable" {
+            return true
+        }
+
+        assert!(custom.payload().len() % 4 == 0);
+        let mut payload = unsafe {
+            slice::from_raw_parts(custom.payload().as_ptr() as *const Unaligned,
+                                  custom.payload().len() / 4)
         };
 
-    for entry in data.entries_mut() {
-        let mut value = bytes_to_u32(entry.value_mut());
-        let mut tmp = &mut *value;
-        loop {
-            let value = tmp;
-            let start = match value.iter().position(|i| i.0 == 0x30d97887) {
-                Some(i) => i,
-                None => break,
-            };
-            if value.get(start + 1).map(|c| c.0) != Some(0xd4182f61) {
-                tmp = &mut value[1..];
-                continue
-            }
-            let cnt = value[start + 2].0 as usize;
-            let (a, b) = value[start..].split_at_mut(cnt + 3);
-            tmp = b;
-            let json = a[3..].iter()
-                .map(|i| char::from_u32(i.0).unwrap())
+        while payload.len() > 0 {
+            let len = payload[0].0.to_le();
+            assert!(len % 4 == 0);
+            let (a, b) = payload[1..].split_at((len / 4) as usize);
+            payload = b;
+            let json = a.iter()
+                .map(|i| char::from_u32(i.0.to_le()).unwrap())
                 .collect::<String>();
             let p: shared::Program = match serde_json::from_str(&json) {
                 Ok(f) => f,
@@ -200,57 +191,9 @@ to open an issue at https://github.com/alexcrichton/wasm-bindgen/issues!
     p.version, version);
             }
             ret.push(p);
+        }
 
-            for slot in a {
-                slot.0 = 0;
-            }
-        }
-    }
+        false
+    });
     return ret
 }
-
-#[repr(packed)]
-struct Unaligned(u32);
-
-struct FutzWithAlign<'a> {
-    data: &'a mut Vec<u8>,
-    len: usize,
-}
-
-fn bytes_to_u32(a: &mut Vec<u8>) -> FutzWithAlign {
-    let prev_len = a.len();
-    // Data implicitly contains zeros after it and it looks like LLD exploits
-    // this. Pad our view into the vector with zeros to make sure that we read
-    // off everything when we iterate. After we're done iterating though we put
-    // this back as we found it, hence the newtype wrapper w/ a dtor.
-    while a.len() % 4 != 0 {
-        a.push(0);
-    }
-    FutzWithAlign { data: a, len: prev_len }
-}
-
-impl<'a> Deref for FutzWithAlign<'a> {
-    type Target = [Unaligned];
-
-    fn deref(&self) -> &[Unaligned] {
-        unsafe {
-            slice::from_raw_parts(self.data.as_ptr() as *const Unaligned,
-                                  self.data.len() / 4)
-        }
-    }
-}
-
-impl<'a> DerefMut for FutzWithAlign<'a> {
-    fn deref_mut(&mut self) -> &mut [Unaligned] {
-        unsafe {
-            slice::from_raw_parts_mut(self.data.as_mut_ptr() as *mut Unaligned,
-                                      self.data.len() / 4)
-        }
-    }
-}
-
-impl<'a> Drop for FutzWithAlign<'a> {
-    fn drop(&mut self) {
-        self.data.truncate(self.len);
-    }
-}

crates/wasm-bindgen-macro/src/ast.rs

@@ -404,12 +404,13 @@ impl Program {
         };
         let cnt = cnt as u32;
         (quote! {
-            0x30d97887,
-            0xd4182f61,
-            #cnt,
+            (#cnt >> 0) as u8,
+            (#cnt >> 8) as u8,
+            (#cnt >> 16) as u8,
+            (#cnt >> 24) as u8
         }).to_tokens(dst);
         tmp.to_tokens(dst);
-        (cnt as usize) + 3
+        (cnt as usize) + 4
     }
 }
 

crates/wasm-bindgen-macro/src/lib.rs

@@ -110,9 +110,9 @@ impl ToTokens for ast::Program {
         let generated_static_length = self.literal(&mut generated_static_value);
 
         (my_quote! {
-            #[no_mangle]
             #[allow(non_upper_case_globals)]
-            pub static #generated_static_name: [u32; #generated_static_length] =
+            #[wasm_custom_section = "__wasm_bindgen_unstable"]
+            const #generated_static_name: [u8; #generated_static_length] =
                 [#generated_static_value];
         }).to_tokens(tokens);
     }
@@ -565,6 +565,7 @@ impl ToTokens for ast::ImportFunction {
             #[allow(bad_style)]
             #vis extern #fn_token #rust_name(#me #(#arguments),*) #ret {
                 ::wasm_bindgen::__rt::link_this_library();
+                #[wasm_import_module = "__wbindgen_placeholder__"]
                 extern {
                     fn #import_name(#(#abi_arguments),*) -> #abi_ret;
                 }
@@ -638,6 +639,7 @@ impl ToTokens for ast::ImportStatic {
             #[allow(bad_style)]
             #vis static #name: ::wasm_bindgen::JsStatic<#ty> = {
                 fn init() -> #ty {
+                    #[wasm_import_module = "__wbindgen_placeholder__"]
                     extern {
                         fn #shim_name() -> u32;
                     }

crates/wasm-bindgen-macro/src/literal.rs

@@ -21,12 +21,18 @@ impl<'a> LiteralBuilder<'a> {
         self.cnt
     }
 
-    fn char_lit(&mut self, c: char) {
-        if self.cnt > 0 {
+    fn byte(&mut self, b: u8) {
         ::syn::token::Comma::default().to_tokens(self.dst);
-        }
         self.cnt += 1;
-        (c as u32).to_tokens(self.dst);
+        b.to_tokens(self.dst);
+    }
+
+    fn char_lit(&mut self, c: char) {
+        let c = c as u32;
+        self.byte(c as u8);
+        self.byte((c >> 8) as u8);
+        self.byte((c >> 16) as u8);
+        self.byte((c >> 24) as u8);
     }
 
     fn append(&mut self, s: &str) {
@@ -57,9 +63,13 @@ impl<'a> LiteralBuilder<'a> {
 
     fn as_char(&mut self, tokens: Tokens) {
         self.append("\"");
-        ::syn::token::Comma::default().to_tokens(self.dst);
-        tokens.to_tokens(self.dst);
-        self.cnt += 1;
+        (quote! {
+            , (((#tokens) as u32) >> 0) as u8
+            , (((#tokens) as u32) >> 8) as u8
+            , (((#tokens) as u32) >> 16) as u8
+            , (((#tokens) as u32) >> 24) as u8
+        }).to_tokens(self.dst);
+        self.cnt += 4;
         self.append("\"");
     }
 

examples/console_log/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

examples/dom/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

examples/hello_world/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

examples/math/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

examples/performance/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 extern crate humantime;

examples/smorgasboard/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

examples/wasm-in-wasm/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(proc_macro)]
+#![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
 extern crate wasm_bindgen;
 

src/lib.rs

@@ -5,7 +5,7 @@
 //! this crate and this crate also provides JS bindings through the `JsValue`
 //! interface.
 
-#![feature(use_extern_macros, try_reserve)]
+#![feature(use_extern_macros, wasm_import_module, try_reserve)]
 
 extern crate wasm_bindgen_macro;
 
@@ -213,6 +213,7 @@ macro_rules! numbers {
 
 numbers! { i8 u8 i16 u16 i32 u32 f32 f64 }
 
+#[wasm_import_module = "__wbindgen_placeholder__"]
 extern {
     fn __wbindgen_object_clone_ref(idx: u32) -> u32;
     fn __wbindgen_object_drop_ref(idx: u32);
@@ -228,6 +229,7 @@ extern {
     fn __wbindgen_symbol_new(ptr: *const u8, len: usize) -> u32;
     fn __wbindgen_is_symbol(idx: u32) -> u32;
     fn __wbindgen_string_get(idx: u32, len: *mut usize) -> *mut u8;
+    fn __wbindgen_throw(a: *const u8, b: usize) -> !;
 }
 
 impl Clone for JsValue {
@@ -298,9 +300,6 @@ impl<T: WasmBoundary> Deref for JsStatic<T> {
 #[cold]
 #[inline(never)]
 pub fn throw(s: &str) -> ! {
-    extern {
-        fn __wbindgen_throw(a: *const u8, b: usize) -> !;
-    }
     unsafe {
         __wbindgen_throw(s.as_ptr(), s.len());
     }

tests/api.rs

@@ -5,7 +5,7 @@ fn works() {
     test_support::project()
         .detect_node(true)
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 

tests/classes.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn simple() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -56,7 +56,7 @@ fn simple() {
 fn strings() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -114,7 +114,7 @@ fn strings() {
 fn exceptions() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -179,7 +179,7 @@ fn exceptions() {
 fn pass_one_to_another() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -229,7 +229,7 @@ fn pass_one_to_another() {
 fn pass_into_js() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -276,7 +276,7 @@ fn pass_into_js() {
 fn issue_27() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
             use wasm_bindgen::prelude::*;

tests/dependencies.rs

@@ -6,7 +6,7 @@ fn dependencies_work() {
         .file(
             "src/lib.rs",
             r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
             extern crate wasm_bindgen;
             extern crate dependency;
             use wasm_bindgen::prelude::*;
@@ -51,7 +51,7 @@ fn dependencies_work() {
         .file(
             "vendor/dependency/src/lib.rs",
             r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
             extern crate wasm_bindgen;
             use wasm_bindgen::prelude::*;
 

tests/enums.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn c_style_enum() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -46,7 +46,7 @@ fn c_style_enum() {
 fn c_style_enum_with_custom_values() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 

tests/import-class.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn simple() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -44,7 +44,7 @@ fn simple() {
 fn import_class() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -87,7 +87,7 @@ fn import_class() {
 fn construct() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -159,7 +159,7 @@ fn construct() {
 fn new_constructors() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -204,7 +204,7 @@ fn new_constructors() {
 fn switch_methods() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -283,7 +283,7 @@ fn switch_methods() {
 fn properties() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -340,7 +340,7 @@ fn properties() {
 fn rename_setter_getter() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 

tests/imports.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn simple() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -86,7 +86,7 @@ fn simple() {
 fn unused() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -116,7 +116,7 @@ fn unused() {
 fn strings() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -157,7 +157,7 @@ fn strings() {
 fn exceptions() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -215,7 +215,7 @@ fn exceptions() {
 fn exn_caught() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -253,7 +253,7 @@ fn exn_caught() {
 fn free_imports() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -283,7 +283,7 @@ fn free_imports() {
 fn import_a_field() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -315,7 +315,7 @@ fn import_a_field() {
 fn rename() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 

tests/jsobjects.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn simple() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -45,7 +45,7 @@ fn simple() {
 fn owned() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -86,7 +86,7 @@ fn owned() {
 fn clone() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -133,7 +133,7 @@ fn clone() {
 fn promote() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 
@@ -177,7 +177,7 @@ fn promote() {
 fn returning_vector() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 

tests/math.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn auto_bind_math() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 

tests/non-debug.rs

@@ -5,7 +5,7 @@ fn works() {
     test_support::project()
         .debug(false)
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 

tests/simple.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn add() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -57,7 +57,7 @@ fn add() {
 fn string_arguments() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -89,7 +89,7 @@ fn string_arguments() {
 fn return_a_string() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -123,7 +123,7 @@ fn return_a_string() {
 fn exceptions() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -154,7 +154,7 @@ fn exceptions() {
 // fn other_imports() {
 //     test_support::project()
 //         .file("src/lib.rs", r#"
-//             #![feature(proc_macro)]
+//             #![feature(proc_macro, wasm_custom_section)]
 //
 //             extern crate wasm_bindgen;
 //

tests/slice.rs

@@ -4,7 +4,7 @@ extern crate test_support;
 fn export() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section)]
 
             extern crate wasm_bindgen;
 
@@ -84,7 +84,7 @@ fn export() {
 fn import() {
     test_support::project()
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;
 

tests/structural.rs

@@ -5,7 +5,7 @@ fn works() {
     test_support::project()
         .detect_node(true)
         .file("src/lib.rs", r#"
-            #![feature(proc_macro)]
+            #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
 
             extern crate wasm_bindgen;