perf: remove double check for keywords in readWord

Instead of calling isKeyword we simple check directly if the keyword token is available

packages/babel-parser/src/parser/expression.js

@@ -24,6 +24,7 @@ import LValParser from "./lval";
 import {
   isStrictReservedWord,
   isStrictBindReservedWord,
+  isKeyword,
 } from "../util/identifier";
 import type { Pos, Position } from "../util/location";
 import * as charCodes from "charcodes";
@@ -2020,7 +2021,7 @@ export default class ExpressionParser extends LValParser {
       );
     }
 
-    if (this.isReservedWord(word) || (checkKeywords && this.isKeyword(word))) {
+    if (this.isReservedWord(word) || (checkKeywords && isKeyword(word))) {
       this.raise(startLoc, word + " is a reserved word");
     }
   }

packages/babel-parser/src/plugins/flow.js

@@ -1190,9 +1190,6 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         case "any":
           return this.finishNode(node, "AnyTypeAnnotation");
 
-        case "void":
-          return this.finishNode(node, "VoidTypeAnnotation");
-
         case "bool":
         case "boolean":
           return this.finishNode(node, "BooleanTypeAnnotation");
@@ -1369,6 +1366,10 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             "NumberLiteralTypeAnnotation",
           );
 
+        case tt._void:
+          this.next();
+          return this.finishNode(node, "VoidTypeAnnotation");
+
         case tt._null:
           this.next();
           return this.finishNode(node, "NullLiteralTypeAnnotation");
@@ -1922,16 +1923,6 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       }
     }
 
-    // don't consider `void` to be a keyword as then it'll use the void token type
-    // and set startExpr
-    isKeyword(name: string): boolean {
-      if (this.state.inType && name === "void") {
-        return false;
-      } else {
-        return super.isKeyword(name);
-      }
-    }
-
     // ensure that inside flow types, we bypass the jsx parser plugin
     getTokenFromCode(code: number): void {
       const next = this.state.input.charCodeAt(this.state.pos + 1);

packages/babel-parser/src/tokenizer/index.js

@@ -3,11 +3,7 @@
 import type { Options } from "../options";
 import type { Position } from "../util/location";
 import * as charCodes from "charcodes";
-import {
-  isIdentifierStart,
-  isIdentifierChar,
-  isKeyword,
-} from "../util/identifier";
+import { isIdentifierStart, isIdentifierChar } from "../util/identifier";
 import { types as tt, keywords as keywordTypes, type TokenType } from "./types";
 import { type TokContext, types as ct } from "./context";
 import LocationParser from "../parser/location";
@@ -157,12 +153,6 @@ export default class Tokenizer extends LocationParser {
 
   // TODO
 
-  isKeyword(word: string): boolean {
-    return isKeyword(word);
-  }
-
-  // TODO
-
   lookahead(): State {
     const old = this.state;
     this.state = old.clone(true);
@@ -1336,14 +1326,10 @@ export default class Tokenizer extends LocationParser {
 
   readWord(): void {
     const word = this.readWord1();
-    let type = tt.name;
+    const type = keywordTypes[word] || tt.name;
 
-    if (this.isKeyword(word)) {
-      if (this.state.containsEsc) {
-        this.raise(this.state.pos, `Escape sequence in keyword ${word}`);
-      }
-
-      type = keywordTypes[word];
+    if (type.keyword && this.state.containsEsc) {
+      this.raise(this.state.pos, `Escape sequence in keyword ${word}`);
     }
 
     // Allow @@iterator and @@asyncIterator as a identifier only inside type

packages/babel-parser/src/tokenizer/types.js

@@ -133,20 +133,20 @@ export const types: { [name: string]: TokenType } = {
   incDec: new TokenType("++/--", { prefix, postfix, startsExpr }),
   bang: new TokenType("!", { beforeExpr, prefix, startsExpr }),
   tilde: new TokenType("~", { beforeExpr, prefix, startsExpr }),
-  pipeline: new BinopTokenType("|>", 0),
-  nullishCoalescing: new BinopTokenType("??", 1),
-  logicalOR: new BinopTokenType("||", 1),
-  logicalAND: new BinopTokenType("&&", 2),
-  bitwiseOR: new BinopTokenType("|", 3),
-  bitwiseXOR: new BinopTokenType("^", 4),
-  bitwiseAND: new BinopTokenType("&", 5),
-  equality: new BinopTokenType("==/!=", 6),
-  relational: new BinopTokenType("</>", 7),
-  bitShift: new BinopTokenType("<</>>", 8),
+  pipeline: BinopTokenType("|>", 0),
+  nullishCoalescing: BinopTokenType("??", 1),
+  logicalOR: BinopTokenType("||", 1),
+  logicalAND: BinopTokenType("&&", 2),
+  bitwiseOR: BinopTokenType("|", 3),
+  bitwiseXOR: BinopTokenType("^", 4),
+  bitwiseAND: BinopTokenType("&", 5),
+  equality: BinopTokenType("==/!=", 6),
+  relational: BinopTokenType("</>", 7),
+  bitShift: BinopTokenType("<</>>", 8),
   plusMin: new TokenType("+/-", { beforeExpr, binop: 9, prefix, startsExpr }),
-  modulo: new BinopTokenType("%", 10),
-  star: new BinopTokenType("*", 10),
-  slash: new BinopTokenType("/", 10),
+  modulo: BinopTokenType("%", 10),
+  star: BinopTokenType("*", 10),
+  slash: BinopTokenType("/", 10),
   exponent: new TokenType("**", {
     beforeExpr,
     binop: 11,
@@ -154,45 +154,53 @@ export const types: { [name: string]: TokenType } = {
   }),
 };
 
-export const keywords = {
-  break: new KeywordTokenType("break"),
-  case: new KeywordTokenType("case", { beforeExpr }),
-  catch: new KeywordTokenType("catch"),
-  continue: new KeywordTokenType("continue"),
-  debugger: new KeywordTokenType("debugger"),
-  default: new KeywordTokenType("default", { beforeExpr }),
-  do: new KeywordTokenType("do", { isLoop, beforeExpr }),
-  else: new KeywordTokenType("else", { beforeExpr }),
-  finally: new KeywordTokenType("finally"),
-  for: new KeywordTokenType("for", { isLoop }),
-  function: new KeywordTokenType("function", { startsExpr }),
-  if: new KeywordTokenType("if"),
-  return: new KeywordTokenType("return", { beforeExpr }),
-  switch: new KeywordTokenType("switch"),
-  throw: new KeywordTokenType("throw", { beforeExpr, prefix, startsExpr }),
-  try: new KeywordTokenType("try"),
-  var: new KeywordTokenType("var"),
-  let: new KeywordTokenType("let"),
-  const: new KeywordTokenType("const"),
-  while: new KeywordTokenType("while", { isLoop }),
-  with: new KeywordTokenType("with"),
-  new: new KeywordTokenType("new", { beforeExpr, startsExpr }),
-  this: new KeywordTokenType("this", { startsExpr }),
-  super: new KeywordTokenType("super", { startsExpr }),
-  class: new KeywordTokenType("class", { startsExpr }),
-  extends: new KeywordTokenType("extends", { beforeExpr }),
-  export: new KeywordTokenType("export"),
-  import: new KeywordTokenType("import", { startsExpr }),
-  yield: new KeywordTokenType("yield", { beforeExpr, startsExpr }),
-  null: new KeywordTokenType("null", { startsExpr }),
-  true: new KeywordTokenType("true", { startsExpr }),
-  false: new KeywordTokenType("false", { startsExpr }),
-  in: new KeywordTokenType("in", { beforeExpr, binop: 7 }),
-  instanceof: new KeywordTokenType("instanceof", { beforeExpr, binop: 7 }),
-  typeof: new KeywordTokenType("typeof", { beforeExpr, prefix, startsExpr }),
-  void: new KeywordTokenType("void", { beforeExpr, prefix, startsExpr }),
-  delete: new KeywordTokenType("delete", { beforeExpr, prefix, startsExpr }),
-};
+function makeKeywordProps(
+  name: string,
+  conf: any,
+): PropertyDescriptor<TokenType> {
+  return { value: KeywordTokenType(name, conf), enumerable: true };
+}
+
+// $FlowIssue
+export const keywords = Object.create(null, {
+  break: makeKeywordProps("break"),
+  case: makeKeywordProps("case", { beforeExpr }),
+  catch: makeKeywordProps("catch"),
+  continue: makeKeywordProps("continue"),
+  debugger: makeKeywordProps("debugger"),
+  default: makeKeywordProps("default", { beforeExpr }),
+  do: makeKeywordProps("do", { isLoop, beforeExpr }),
+  else: makeKeywordProps("else", { beforeExpr }),
+  finally: makeKeywordProps("finally"),
+  for: makeKeywordProps("for", { isLoop }),
+  function: makeKeywordProps("function", { startsExpr }),
+  if: makeKeywordProps("if"),
+  return: makeKeywordProps("return", { beforeExpr }),
+  switch: makeKeywordProps("switch"),
+  throw: makeKeywordProps("throw", { beforeExpr, prefix, startsExpr }),
+  try: makeKeywordProps("try"),
+  var: makeKeywordProps("var"),
+  let: makeKeywordProps("let"),
+  const: makeKeywordProps("const"),
+  while: makeKeywordProps("while", { isLoop }),
+  with: makeKeywordProps("with"),
+  new: makeKeywordProps("new"),
+  this: makeKeywordProps("this", { startsExpr }),
+  super: makeKeywordProps("super", { startsExpr }),
+  class: makeKeywordProps("class", { startsExpr }),
+  extends: makeKeywordProps("extends", { beforeExpr }),
+  export: makeKeywordProps("export"),
+  import: makeKeywordProps("import", { startsExpr }),
+  yield: makeKeywordProps("yield", { beforeExpr, startsExpr }),
+  null: makeKeywordProps("null", { startsExpr }),
+  true: makeKeywordProps("true", { startsExpr }),
+  false: makeKeywordProps("false", { startsExpr }),
+  in: makeKeywordProps("in", { beforeExpr, binop: 7 }),
+  instanceof: makeKeywordProps("instanceof", { beforeExpr, binop: 7 }),
+  typeof: makeKeywordProps("typeof", { beforeExpr, prefix, startsExpr }),
+  void: makeKeywordProps("void", { beforeExpr, prefix, startsExpr }),
+  delete: makeKeywordProps("delete", { beforeExpr, prefix, startsExpr }),
+});
 
 // Map keyword names to token types.
 Object.keys(keywords).forEach(name => {