babel/packages/babel-plugin-transform-function-bind/src/index.js

export default function ({ types: t }) {
  function getTempId(scope) {
    let id = scope.path.getData("functionBind");
    if (id) return id;

    id = scope.generateDeclaredUidIdentifier("context");
    return scope.path.setData("functionBind", id);
  }

  function getStaticContext(bind, scope) {
    let object = bind.object || bind.callee.object;
    return scope.isStatic(object) && object;
  }

  function inferBindContext(bind, scope) {
    let staticContext = getStaticContext(bind, scope);
    if (staticContext) return staticContext;

    let tempId = getTempId(scope);
    if (bind.object) {
      bind.callee = t.sequenceExpression([
        t.assignmentExpression("=", tempId, bind.object),
        bind.callee
      ]);
    } else {
      bind.callee.object = t.assignmentExpression("=", tempId, bind.callee.object);
    }
    return tempId;
  }

  return {
    inherits: require("babel-plugin-syntax-function-bind"),

    visitor: {
      CallExpression({ node, scope }) {
        let bind = node.callee;
        if (!t.isBindExpression(bind)) return;

        let context = inferBindContext(bind, scope);
        node.callee = t.memberExpression(bind.callee, t.identifier("call"));
        node.arguments.unshift(context);
      },

      BindExpression(path) {
        let { node, scope } = path;
        let context = inferBindContext(node, scope);
        path.replaceWith(t.callExpression(t.memberExpression(node.callee, t.identifier("bind")), [context]));
      }
    }
  };
}