Revert "Remove Flow annotations and pragmas"

This reverts commit 4252244d06.

src/tokenizer/context.js

@@ -1,3 +1,4 @@
+/* @flow */
 
 // The algorithm used to determine whether a regexp can appear at a
 // given point in the program is loosely based on sweet.js' approach.
@@ -7,16 +8,27 @@ import { types as tt } from "./types";
 import { lineBreak } from "../util/whitespace";
 
 export class TokContext {
-  constructor(token, isExpr, preserveSpace, override) {
+  constructor(
+    token: string,
+    isExpr?: boolean,
+    preserveSpace?: boolean,
+    override?: Function,
+  ) {
     this.token = token;
     this.isExpr = !!isExpr;
     this.preserveSpace = !!preserveSpace;
     this.override = override;
   }
 
+  token: string;
+  isExpr: boolean;
+  preserveSpace: boolean;
+  override: ?Function;
 }
 
-export const types = {
+export const types: {
+  [key: string]: TokContext;
+} = {
   b_stat: new TokContext("{", false),
   b_expr: new TokContext("{", true),
   b_tmpl: new TokContext("${", true),

src/tokenizer/index.js

@@ -1,6 +1,7 @@
 /* eslint max-len: 0 */
 /* eslint indent: 0 */
 
+import type { TokenType } from "./types";
 import { isIdentifierStart, isIdentifierChar, isKeyword } from "../util/identifier";
 import { types as tt, keywords as keywordTypes } from "./types";
 import { types as ct } from "./context";
@@ -21,6 +22,11 @@ export class Token {
     this.loc = new SourceLocation(state.startLoc, state.endLoc);
   }
 
+  type: TokenType;
+  value: any;
+  start: number;
+  end: number;
+  loc: SourceLocation;
 }
 
 // ## Tokenizer