Type-check CommentsParser and LocationParser (#484)

.flowconfig

@@ -11,3 +11,4 @@
 strip_root=true
 suppress_comment= \\(.\\|\n\\)*\\$FlowFixMe
 suppress_comment= \\(.\\|\n\\)*\\$FlowIssue
+suppress_comment= \\(.\\|\n\\)*\\$FlowIgnore

src/parser/base.js

@@ -3,6 +3,8 @@
 import type { Options } from "../options";
 import { reservedWords } from "../util/identifier";
 
+import type State from "../tokenizer/state";
+
 export default class BaseParser {
   // Properties set by constructor in index.js
   options: Options;
@@ -10,6 +12,11 @@ export default class BaseParser {
   plugins: { [key: string]: boolean };
   filename: ?string;
 
+  // Initialized by Tokenizer
+  state: State;
+  input: string;
+
+
   isReservedWord(word: string): boolean {
     if (word === "await") {
       return this.inModule;

src/parser/comments.js

@@ -1,5 +1,7 @@
 /* eslint max-len: 0 */
 
+// @flow
+
 /**
  * Based on the comment attachment algorithm used in espree and estraverse.
  *
@@ -25,19 +27,20 @@
  */
 
 import BaseParser from "./base";
+import type { Comment, Node } from "../types";
 
 function last(stack) {
   return stack[stack.length - 1];
 }
 
 export default class CommentsParser extends BaseParser {
-  addComment(comment) {
+  addComment(comment: Comment): void {
     if (this.filename) comment.loc.filename = this.filename;
     this.state.trailingComments.push(comment);
     this.state.leadingComments.push(comment);
   }
 
-  processComment(node) {
+  processComment(node: Node): void {
     if (node.type === "Program" && node.body.length > 0) return;
 
     const stack = this.state.commentStack;
@@ -127,10 +130,8 @@ export default class CommentsParser extends BaseParser {
         // that comes after the node. Keep in mind that this could
         // result in an empty array, and if so, the array must be
         // deleted.
-        node.leadingComments = this.state.leadingComments.slice(0, i);
-        if ((node.leadingComments: Array<any>).length === 0) {
-          node.leadingComments = null;
-        }
+        const leadingComments = this.state.leadingComments.slice(0, i);
+        node.leadingComments = leadingComments.length === 0 ? null : leadingComments;
 
         // Similarly, trailing comments are attached later. The variable
         // must be reset to null if there are no trailing comments.

src/parser/location.js

@@ -1,3 +1,5 @@
+// @flow
+
 import { getLineInfo } from "../util/location";
 import CommentsParser from "./comments";
 
@@ -8,10 +10,11 @@ import CommentsParser from "./comments";
 // message.
 
 export default class LocationParser extends CommentsParser {
-  raise(pos, message) {
+  raise(pos: number, message: string): empty {
     const loc = getLineInfo(this.input, pos);
     message += ` (${loc.line}:${loc.column})`;
-    const err = new SyntaxError(message);
+    // $FlowIgnore
+    const err: SyntaxError & { pos: number, loc: Position } = new SyntaxError(message);
     err.pos = pos;
     err.loc = loc;
     throw err;

src/tokenizer/index.js

@@ -49,9 +49,7 @@ export default class Tokenizer extends LocationParser {
   // parser/util.js
   +unexpected: (pos?: ?number, messageOrType?: string | TokenType) => empty;
 
-  state: State;
   isLookahead: boolean;
-  input: string;
 
   constructor(options: Options, input: string) {
     super();