diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index 74f78c6047ac..ca62723b0dca 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -45,6 +45,7 @@ import { ExpressionErrors } from "./util";
 
 export default class ExpressionParser extends LValParser {
   // Forward-declaration: defined in statement.js
+  /*::
   +parseBlock: (
     allowDirectives?: boolean,
     createNewLexicalScope?: boolean,
@@ -63,6 +64,7 @@ export default class ExpressionParser extends LValParser {
   ) => T;
   +parseFunctionParams: (node: N.Function, allowModifiers?: boolean) => void;
   +takeDecorators: (node: N.HasDecorators) => void;
+  */
 
   // Check if property __proto__ has been used more than once.
   // If the expression is a destructuring assignment, then __proto__ may appear
diff --git a/packages/babel-parser/src/parser/index.js b/packages/babel-parser/src/parser/index.js
index d3f5db419c6b..e557afa43f92 100644
--- a/packages/babel-parser/src/parser/index.js
+++ b/packages/babel-parser/src/parser/index.js
@@ -1,7 +1,7 @@
 // @flow
 
 import type { Options } from "../options";
-import type { File, JSXOpeningElement } from "../types";
+import type { File /*::, JSXOpeningElement */ } from "../types";
 import type { PluginList } from "../plugin-utils";
 import { getOptions } from "../options";
 import StatementParser from "./statement";
@@ -13,9 +13,11 @@ export type PluginsMap = Map<string, { [string]: any }>;
 
 export default class Parser extends StatementParser {
   // Forward-declaration so typescript plugin can override jsx plugin
+  /*::
   +jsxParseOpeningElementAfterName: (
     node: JSXOpeningElement,
   ) => JSXOpeningElement;
+  */
 
   constructor(options: ?Options, input: string) {
     options = getOptions(options);
diff --git a/packages/babel-parser/src/parser/location.js b/packages/babel-parser/src/parser/location.js
index 3694a567090a..21c08a581239 100644
--- a/packages/babel-parser/src/parser/location.js
+++ b/packages/babel-parser/src/parser/location.js
@@ -10,7 +10,10 @@ import CommentsParser from "./comments";
 // message.
 
 export default class LocationParser extends CommentsParser {
+  // Forward-declaration: defined in tokenizer/index.js
+  /*::
   +isLookahead: boolean;
+  */
 
   getLocationForPosition(pos: number): Position {
     let loc;
diff --git a/packages/babel-parser/src/parser/lval.js b/packages/babel-parser/src/parser/lval.js
index 51de283f5be7..ce81dccd8c7c 100644
--- a/packages/babel-parser/src/parser/lval.js
+++ b/packages/babel-parser/src/parser/lval.js
@@ -6,13 +6,13 @@ import type {
   TSParameterProperty,
   Decorator,
   Expression,
-  Identifier,
   Node,
-  ObjectExpression,
-  ObjectPattern,
   Pattern,
   RestElement,
   SpreadElement,
+  /*:: Identifier, */
+  /*:: ObjectExpression, */
+  /*:: ObjectPattern, */
 } from "../types";
 import type { Pos, Position } from "../util/location";
 import {
@@ -31,6 +31,7 @@ const unwrapParenthesizedExpression = (node: Node) => {
 
 export default class LValParser extends NodeUtils {
   // Forward-declaration: defined in expression.js
+  /*::
   +parseIdentifier: (liberal?: boolean) => Identifier;
   +parseMaybeAssign: (
     noIn?: ?boolean,
@@ -42,8 +43,11 @@ export default class LValParser extends NodeUtils {
     isPattern: boolean,
     refExpressionErrors?: ?ExpressionErrors,
   ) => T;
+  */
   // Forward-declaration: defined in statement.js
+  /*::
   +parseDecorator: () => Decorator;
+  */
 
   // Convert existing expression atom to assignable pattern
   // if possible.
diff --git a/packages/babel-parser/src/tokenizer/index.js b/packages/babel-parser/src/tokenizer/index.js
index 8558137f719f..f75ee0acdc5a 100644
--- a/packages/babel-parser/src/tokenizer/index.js
+++ b/packages/babel-parser/src/tokenizer/index.js
@@ -111,7 +111,9 @@ export class Token {
 export default class Tokenizer extends LocationParser {
   // Forward-declarations
   // parser/util.js
+  /*::
   +unexpected: (pos?: ?number, messageOrType?: string | TokenType) => empty;
+  */
 
   isLookahead: boolean;
 
diff --git a/packages/babel-parser/src/util/scope.js b/packages/babel-parser/src/util/scope.js
index 1cbf06fb671f..9205547b729b 100644
--- a/packages/babel-parser/src/util/scope.js
+++ b/packages/babel-parser/src/util/scope.js
@@ -92,7 +92,7 @@ export default class ScopeHandler<IScope: Scope = Scope> {
     return new Scope(flags);
   }
   // This method will be overwritten by subclasses
-  +createScope: (flags: ScopeFlags) => IScope;
+  /*:: +createScope: (flags: ScopeFlags) => IScope; */
 
   enter(flags: ScopeFlags) {
     this.scopeStack.push(this.createScope(flags));