Flow opaque type aliases

packages/babel-generator/src/generators/flow.js

@@ -75,6 +75,14 @@ export function DeclareTypeAlias(node: Object) {
   this.TypeAlias(node);
 }
 
+export function DeclareOpaqueType(node: Object, parent: Object) {
+  if (!t.isDeclareExportDeclaration(parent)) {
+    this.word("declare");
+    this.space();
+  }
+  this.OpaqueType(node);
+}
+
 export function DeclareVariable(node: Object, parent: Object) {
   if (!t.isDeclareExportDeclaration(parent)) {
     this.word("declare");
@@ -290,6 +298,27 @@ export function TypeAlias(node: Object) {
   this.semicolon();
 }
 
+export function OpaqueType(node: Object) {
+  this.word("opaque");
+  this.space();
+  this.word("type");
+  this.space();
+  this.print(node.id, node);
+  this.print(node.typeParameters, node);
+  if (node.supertype) {
+    this.token(":");
+    this.space();
+    this.print(node.supertype, node);
+  }
+  if (node.impltype) {
+    this.space();
+    this.token("=");
+    this.space();
+    this.print(node.impltype, node);
+  }
+  this.semicolon();
+}
+
 export function TypeAnnotation(node: Object) {
   this.token(":");
   this.space();

packages/babel-generator/test/fixtures/flow/declare-exports/actual.js

@@ -22,3 +22,10 @@ declare module B {
   declare export type B = {};
   declare export interface Moon {}
 }
+
+declare export opaque type Foo;
+declare export opaque type Bar<T>;
+declare export opaque type Baz: Foo;
+declare export opaque type Foo<T>: Bar<T>;
+declare export opaque type Foo<T>: Bar;
+declare export opaque type Foo: Bar<T>;

packages/babel-generator/test/fixtures/flow/declare-exports/expected.js

@@ -29,4 +29,10 @@ declare export { c, d } from 'bar';
 declare module B {
   declare export type B = {};
   declare export interface Moon {}
-}
+}
+declare export opaque type Foo;
+declare export opaque type Bar<T>;
+declare export opaque type Baz: Foo;
+declare export opaque type Foo<T>: Bar<T>;
+declare export opaque type Foo<T>: Bar;
+declare export opaque type Foo: Bar<T>;

packages/babel-generator/test/fixtures/flow/declare-statements/actual.js

@@ -19,3 +19,7 @@ declare type B = {
 declare interface I { foo: string }
 declare interface I<T> { foo: T }
 declare module.exports: { foo: string }
+declare opaque type Foo<T>: Bar<T>;
+declare opaque type ID;
+declare opaque type num: number;
+declare opaque type NumArray;

packages/babel-generator/test/fixtures/flow/declare-statements/expected.js

@@ -38,3 +38,7 @@ declare interface I<T> {
 declare module.exports: {
   foo: string
 }
+declare opaque type Foo<T>: Bar<T>;
+declare opaque type ID;
+declare opaque type num: number;
+declare opaque type NumArray;

packages/babel-generator/test/fixtures/flow/opaque-type-alias/actual.js

@@ -0,0 +1,14 @@
+opaque type ID = string;
+opaque type Foo<T> = Bar<T>;
+opaque type Maybe<T> = _Maybe<T, *>;
+export opaque type Foo = number;
+
+opaque type union =
+ | {type: "A"}
+ | {type: "B"}
+;
+
+opaque type overloads =
+  & ((x: string) => number)
+  & ((x: number) => string)
+;

packages/babel-generator/test/fixtures/flow/opaque-type-alias/expected.js

@@ -0,0 +1,10 @@
+opaque type ID = string;
+opaque type Foo<T> = Bar<T>;
+opaque type Maybe<T> = _Maybe<T, *>;
+export opaque type Foo = number;
+opaque type union = {
+  type: "A"
+} | {
+  type: "B"
+};
+opaque type overloads = (x: string) => number & (x: number) => string;

packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/opaque-type-alias/actual.js

@@ -0,0 +1,15 @@
+function a() {}
+opaque type A = number;
+opaque type B = {
+  name: string;
+};
+
+opaque type union =
+ | {type: "A"}
+ | {type: "B"}
+;
+
+opaque type overloads =
+  & ((x: string) => number)
+  & ((x: number) => string)
+;

packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/opaque-type-alias/expected.js

@@ -0,0 +1,16 @@
+function a() {}
+/*:: opaque type A = number;*/
+
+/*:: opaque type B = {
+  name: string;
+};*/
+
+/*:: opaque type union =
+ | {type: "A"}
+ | {type: "B"}
+;*/
+
+/*:: opaque type overloads =
+  & ((x: string) => number)
+  & ((x: number) => string)
+;*/

packages/babel-plugin-transform-flow-strip-types/test/fixtures/strip-types/strip-opaque-type-alias/actual.js

@@ -0,0 +1,16 @@
+opaque type ID = string;
+opaque type Foo<T> = Bar<T>
+export opaque type Foo = number;
+
+opaque type union =
+ | {type: "A"}
+ | {type: "B"}
+;
+
+opaque type overloads =
+  & ((x: string) => number)
+  & ((x: number) => string)
+;
+
+declare opaque type Foo: Bar;
+declare export opaque type Foo: Bar;

packages/babel-types/src/definitions/flow.js

@@ -101,6 +101,14 @@ defineType("DeclareTypeAlias", {
   },
 });
 
+defineType("DeclareOpaqueType", {
+  visitor: ["id", "typeParameters", "supertype"],
+  aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
+  fields: {
+    // todo
+  },
+});
+
 defineType("DeclareVariable", {
   visitor: ["id"],
   aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
@@ -250,6 +258,14 @@ defineType("TypeAlias", {
   },
 });
 
+defineType("OpaqueType", {
+  visitor: ["id", "typeParameters", "supertype", "impltype"],
+  aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
+  fields: {
+    // todo
+  },
+});
+
 defineType("TypeAnnotation", {
   visitor: ["typeAnnotation"],
   aliases: ["Flow"],

packages/babel-types/src/retrievers.js

@@ -70,6 +70,7 @@ getBindingIdentifiers.keys = {
   DeclareVariable: ["id"],
   InterfaceDeclaration: ["id"],
   TypeAlias: ["id"],
+  OpaqueType: ["id"],
 
   CatchClause: ["param"],
   LabeledStatement: ["label"],