6.0.0

I'm extremely stupid and didn't commit as I go. To anyone reading this
I'm extremely sorry. A lot of these changes are very broad and I plan on
releasing Babel 6.0.0 today live on stage at Ember Camp London so I'm
afraid I couldn't wait. If you're ever in London I'll buy you a beer
(or assorted beverage!) to make up for it, also I'll kiss your feet and
give you a back massage, maybe.

packages/babel-plugin-undeclared-variables-check/.npmignore

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+node_modules
+*.log
+src

packages/babel-plugin-undeclared-variables-check/README.md

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+# babel-plugin-undeclared-variables-check
+
+Throw a compile-time error on references to undeclared variables
+
+## Installation
+
+```sh
+$ npm install babel-plugin-undeclared-variables-check
+```
+
+## Usage
+
+### Via `.babelrc` (Recommended)
+
+**.babelrc**
+
+```json
+{
+  "plugins": ["undeclared-variables-check"]
+}
+```
+
+### Via CLI
+
+```sh
+$ babel --plugins undeclared-variables-check script.js
+```
+
+### Via Node API
+
+```javascript
+require("babel-core").transform("code", {
+  plugins: ["undeclared-variables-check"]
+});
+```

packages/babel-plugin-undeclared-variables-check/package.json

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+{
+  "name": "babel-plugin-undeclared-variables-check",
+  "version": "6.0.6",
+  "description": "Throw a compile-time error on references to undeclared variables",
+  "repository": "babel/babel",
+  "license": "MIT",
+  "main": "lib/index.js",
+  "keywords": [
+    "babel-plugin"
+  ],
+  "dependencies": {
+    "babel-runtime": "^6.0.6",
+    "leven": "^1.0.2"
+  }
+}

packages/babel-plugin-undeclared-variables-check/src/index.js

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+import leven from "leven";
+
+export default function ({ messages }) {
+  return {
+    visitor: {
+      ReferencedIdentifier(path) {
+        let { node, scope } = path;
+
+        let binding = scope.getBinding(node.name);
+        if (binding && binding.kind === "type" && !path.parentPath.isFlow()) {
+          throw path.buildCodeFrameError(messages.get("undeclaredVariableType", node.name), ReferenceError);
+        }
+
+        if (scope.hasBinding(node.name)) return;
+
+        // get the closest declaration to offer as a suggestion
+        // the variable name may have just been mistyped
+
+        let bindings = scope.getAllBindings();
+
+        let closest;
+        let shortest = -1;
+
+        for (let name in bindings) {
+          let distance = leven(node.name, name);
+          if (distance <= 0 || distance > 3) continue;
+          if (distance <= shortest) continue;
+
+          closest = name;
+          shortest = distance;
+        }
+
+        let msg;
+        if (closest) {
+          msg = messages.get("undeclaredVariableSuggestion", node.name, closest);
+        } else {
+          msg = messages.get("undeclaredVariable", node.name);
+        }
+
+        //
+
+        throw path.buildCodeFrameError(msg, ReferenceError);
+      }
+    }
+  };
+}