Update wasm-bindgen rand bindings

src/lib.rs

@@ -229,7 +229,6 @@
 #![cfg_attr(all(feature="alloc", not(feature="std")), feature(alloc))]
 #![cfg_attr(all(feature="simd_support", feature="nightly"), feature(stdsimd))]
 #![cfg_attr(feature = "stdweb", recursion_limit="128")]
-#![cfg_attr(feature = "wasm-bindgen", feature(use_extern_macros))]
 
 #[cfg(feature = "std")] extern crate core;
 #[cfg(all(feature = "alloc", not(feature="std")))] #[macro_use] extern crate alloc;
@@ -898,10 +897,14 @@ pub mod __wbg_shims {
         pub use wasm_bindgen::prelude::*;
 
         #[wasm_bindgen]
-        extern {
-            pub type This;
-            pub static this: This;
+        extern "C" {
+            pub type Function;
+            #[wasm_bindgen(constructor)]
+            pub fn new(s: &str) -> Function;
+            #[wasm_bindgen(method)]
+            pub fn call(this: &Function, self_: &JsValue) -> JsValue;
 
+            pub type This;
             #[wasm_bindgen(method, getter, structural, js_name = self)]
             pub fn self_(me: &This) -> JsValue;
             #[wasm_bindgen(method, getter, structural)]

src/rngs/os.rs

@@ -1121,15 +1121,17 @@ mod imp {
     impl OsRngImpl for OsRng {
         fn new() -> Result<OsRng, Error> {
             // First up we need to detect if we're running in node.js or a
-            // browser. Both environments have `this` defined as an object for
-            // our own scope, and we use that to look up other values.
+            // browser. To do this we get ahold of the `this` object (in a bit
+            // of a roundabout fashion).
             //
-            // Here we test if `this.self` is defined. If so we're in a browser
-            // (either main window or web worker) and if not we're in node. If
-            // it turns out we're in node.js then we require the `crypto`
-            // package and use that. The API we're using was added in Node 6.x
-            // so it should be safe to assume tha it works.
-            if this.self_().is_undefined() {
+            // Once we have `this` we look at its `self` property, which is
+            // only defined on the web (either a main window or web worker).
+            let this = Function::new("return this").call(&JsValue::undefined());
+            assert!(this != JsValue::undefined());
+            let this = This::from(this);
+            let is_browser = this.self_() != JsValue::undefined();
+
+            if !is_browser {
                 return Ok(OsRng::Node(node_require("crypto")))
             }