Make babel-types type checking functions 36% faster (#7685)

* Precompile 25% faster type checking functions

* Pre-fetch type-check function when generating NodePath methods

Additional ~11% speed improvement.

* Slightly faster assert calls

packages/babel-traverse/src/path/index.js

@@ -170,12 +170,13 @@ Object.assign(
 
 for (const type of (t.TYPES: Array<string>)) {
   const typeKey = `is${type}`;
+  const fn = t[typeKey];
   NodePath.prototype[typeKey] = function(opts) {
-    return t[typeKey](this.node, opts);
+    return fn(this.node, opts);
   };
 
   NodePath.prototype[`assert${type}`] = function(opts) {
-    if (!this[typeKey](opts)) {
+    if (!fn(this.node, opts)) {
       throw new TypeError(`Expected node path of type ${type}`);
     }
   };

packages/babel-types/scripts/generators/generateValidators.js

@@ -1,9 +1,31 @@
 "use strict";
 const definitions = require("../../lib/definitions");
 
-function addIsHelper(type) {
+function addIsHelper(type, aliasKeys, deprecated) {
+  const targetType = JSON.stringify(type);
+  let aliasSource = "";
+  if (aliasKeys) {
+    aliasSource =
+      " || " +
+      aliasKeys.map(JSON.stringify).join(" === nodeType || ") +
+      " === nodeType";
+  }
+
   return `export function is${type}(node: Object, opts?: Object): boolean {
-    return is("${type}", node, opts) }
+    ${deprecated || ""}
+    if (!node) return false;
+
+    const nodeType = node.type;
+    if (nodeType === ${targetType}${aliasSource}) {
+      if (typeof opts === "undefined") {
+        return true;
+      } else {
+        return shallowEqual(node, opts);
+      }
+    }
+
+    return false;
+  }
   `;
 }
 
@@ -13,22 +35,20 @@ module.exports = function generateValidators() {
  * This file is auto-generated! Do not modify it directly.
  * To re-generate run 'make build'
  */
-import is from "../is";\n\n`;
+import shallowEqual from "../../utils/shallowEqual";\n\n`;
 
   Object.keys(definitions.VISITOR_KEYS).forEach(type => {
     output += addIsHelper(type);
   });
 
   Object.keys(definitions.FLIPPED_ALIAS_KEYS).forEach(type => {
-    output += addIsHelper(type);
+    output += addIsHelper(type, definitions.FLIPPED_ALIAS_KEYS[type]);
   });
 
   Object.keys(definitions.DEPRECATED_KEYS).forEach(type => {
     const newType = definitions.DEPRECATED_KEYS[type];
-    output += `export function is${type}(node: Object, opts: Object): boolean {
-  console.trace("The node type ${type} has been renamed to ${newType}");
-  return is("${type}", node, opts);
-}\n`;
+    const deprecated = `console.trace("The node type ${type} has been renamed to ${newType}");`;
+    output += addIsHelper(type, null, deprecated);
   });
 
   return output;