add a path hoisting mechanism that will hoist a node to it's highest compatible scope, a compatible scope is considered to be one where all references inside can be resolved to, also adds an optimisation.react.constantElements transformer that uses this to much success facebook/react#3226

src/babel/transformation/transformers/index.js

@@ -18,6 +18,7 @@ export default {
 
   "spec.blockScopedFunctions":             require("./spec/block-scoped-functions"),
 
+  "optimisation.react.constantElements":   require("./optimisation/react.constant-elements"),
   reactCompat:                             require("./other/react-compat"),
   react:                                   require("./other/react"),
 

src/babel/transformation/transformers/optimisation/react.constant-elements.js

@@ -0,0 +1,42 @@
+import * as react from "../../helpers/react";
+
+export var metadata = {
+  optional: true
+};
+
+var immutabilityVisitor = {
+  enter(node, parent, scope, state) {
+    var stop = () => {
+      state.isImmutable = false;
+      this.stop();
+    };
+
+    if (this.isJSXClosingElement()) {
+      this.skip();
+      return;
+    }
+
+    if (this.isJSXIdentifier({ name: "ref" }) && this.parentPath.isJSXAttribute({ name: node })) {
+      return stop();
+    }
+
+    if (this.isJSXIdentifier() || this.isIdentifier() || this.isJSXMemberExpression()) {
+      return;
+    }
+
+    if (!this.isImmutable()) stop();
+  }
+};
+
+export function JSXElement(node, parent, scope, file) {
+  if (node._ignoreConstant) return;
+
+  var state = { isImmutable: true };
+  this.traverse(immutabilityVisitor, state);
+  this.skip();
+
+  if (state.isImmutable) {
+    this.hoist();
+    node._ignoreConstant = true;
+  }
+}

src/babel/traversal/path/hoister.js

@@ -0,0 +1,106 @@
+import * as react from "../../transformation/helpers/react";
+import * as t from "../../types";
+
+var referenceVisitor = {
+  enter(node, parent, scope, state) {
+    if (this.isJSXIdentifier() && react.isCompatTag(node.name)) {
+      return;
+    }
+
+    if (this.isJSXIdentifier() || this.isIdentifier()) {
+      // direct references that we need to track to hoist this to the highest scope we can
+      if (this.isReferenced()) {
+        var bindingInfo = scope.getBinding(node.name);
+
+        if (bindingInfo && bindingInfo.constant) {
+          state.bindings[node.name] = bindingInfo;
+        } else {
+          scope.dump();
+          state.foundIncompatible = true;
+          this.stop();
+        }
+      }
+    }
+  }
+};
+
+export default class PathHoister {
+  constructor(path) {
+    this.foundIncompatible = false;
+    this.bindings          = {};
+    this.scopes            = [];
+    this.path              = path;
+  }
+
+  isCompatibleScope(scope) {
+    for (var key in this.bindings) {
+      var binding = this.bindings[key];
+      if (!scope.bindingIdentifierEquals(key, binding.identifier)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  getCompatibleScopes() {
+    var checkScope = this.path.scope;
+    do {
+      if (this.isCompatibleScope(checkScope)) {
+        this.scopes.push(checkScope);
+      } else {
+        break;
+      }
+    } while(checkScope = checkScope.parent);
+  }
+
+  getAttachmentPath() {
+    var scopes = this.scopes;
+
+    var scope = scopes.pop();
+
+    if (scope.path.isFunction()) {
+      if (this.hasNonParamBindings()) {
+        // can't be attached to this scope
+        return this.getNextScopeStatementParent();
+      } else {
+        // needs to be attached to the body
+        return scope.path.get("body").get("body")[0];
+      }
+    } else if (scope.path.isProgram()) {
+      return this.getNextScopeStatementParent();
+    }
+  }
+
+  getNextScopeStatementParent() {
+    var scope = this.scopes.pop();
+    if (scope) return scope.path.getStatementParent();
+  }
+
+  hasNonParamBindings() {
+    for (var name in this.bindings) {
+      var binding = this.bindings[name];
+      if (binding.kind !== "param") return true;
+    }
+    return false;
+  }
+
+  run() {
+    this.path.traverse(referenceVisitor, this);
+    if (this.foundIncompatible) return;
+
+    this.getCompatibleScopes();
+
+    var path = this.getAttachmentPath();
+    if (!path) return;
+
+    var uid = path.scope.generateUidIdentifier("ref");
+
+    path.insertBefore([
+      t.variableDeclaration("var", [
+        t.variableDeclarator(uid, this.path.node)
+      ])
+    ]);
+
+    this.path.replaceWith(uid);
+  }
+}

src/babel/traversal/path/index.js

@@ -635,6 +635,14 @@ export default class TraversalPath {
 
   traverse(opts, state) {
     traverse(this.node, opts, this.scope, state, this);
+
+  /**
+   * Description
+   */
+
+  hoist() {
+    var hoister = new PathHoister(this);
+    return hoister.run();
   }
 
   /**

src/babel/types/validators.js

@@ -156,11 +156,11 @@ export function isSpecifierDefault(specifier: Object): boolean {
 
 export function isScope(node: Object, parent: Object): boolean {
   if (t.isBlockStatement(node)) {
-    if (t.isLoop(parent.block, { body: node })) {
+    if (t.isLoop(parent, { body: node })) {
       return false;
     }
 
-    if (t.isFunction(parent.block, { body: node })) {
+    if (t.isFunction(parent, { body: node })) {
       return false;
     }
   }

test/core/fixtures/transformation/optimisation-react.constant-elements/constructor/actual.js

@@ -0,0 +1,5 @@
+var Foo = require("Foo");
+
+function render() {
+  return <Foo />;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/constructor/expected.js

@@ -0,0 +1,9 @@
+"use strict";
+
+var Foo = require("Foo");
+
+var _ref = <Foo />;
+
+function render() {
+  return _ref;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/function-parameter/actual.js

@@ -0,0 +1,13 @@
+function render(text) {
+  return function () {
+    return <foo>{text}</foo>;
+  };
+}
+
+var Foo2 = require("Foo");
+
+function createComponent(text) {
+  return function render() {
+    return <Foo2>{text}</Foo2>;
+  };
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/function-parameter/expected.js

@@ -0,0 +1,19 @@
+"use strict";
+
+function render(text) {
+  var _ref = <foo>{text}</foo>;
+
+  return function () {
+    return _ref;
+  };
+}
+
+var Foo2 = require("Foo");
+
+function createComponent(text) {
+  var _ref = <Foo2>{text}</Foo2>;
+
+  return function render() {
+    return _ref;
+  };
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/html-element/actual.js

@@ -0,0 +1,7 @@
+function render() {
+  return <foo />;
+}
+
+function render() {
+  return <div className="foo"><input type="checkbox" checked={true} /></div>;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/html-element/expected.js

@@ -0,0 +1,13 @@
+"use strict";
+
+var _ref = <foo />;
+
+function render() {
+  return _ref;
+}
+
+var _ref = <div className="foo"><input type="checkbox" checked={true} /></div>;
+
+function render() {
+  return _ref;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/inner-declaration/actual.js

@@ -0,0 +1,6 @@
+function render() {
+  var text = getText();
+  return function () {
+    return <foo>{text}</foo>;
+  };
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/inner-declaration/expected.js

@@ -0,0 +1,11 @@
+"use strict";
+
+function render() {
+  var text = getText();
+
+  var _ref = <foo>{text}</foo>;
+
+  return function () {
+    return _ref;
+  };
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/options.json

@@ -0,0 +1,5 @@
+{
+  "noCheckAst": true,
+  "optional": ["optimisation.react.constantElements"],
+  "blacklist": ["react"]
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/ref-deopt/actual.js

@@ -0,0 +1,3 @@
+function render() {
+  return <foo ref="foobar" />;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/ref-deopt/expected.js

@@ -0,0 +1,5 @@
+"use strict";
+
+function render() {
+  return <foo ref="foobar" />;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/spread-deopt/actual.js

@@ -0,0 +1,3 @@
+function render() {
+  return <foo {...foobar} />;
+}

test/core/fixtures/transformation/optimisation-react.constant-elements/spread-deopt/expected.js

@@ -0,0 +1,5 @@
+"use strict";
+
+function render() {
+  return <foo {...foobar} />;
+}