Add support for ForOfStatement with await flag (#1073)

* Enable babylon on flow async_iteration tests

* Add support for ForOfStatement with await flag

src/printer.js

@@ -1064,24 +1064,25 @@ function genericPrintNoParens(path, options, print) {
         ")",
         adjustClause(path.call(print, "body"), options)
       ]);
+
     case "ForOfStatement":
-      return concat([
-        "for (",
-        path.call(print, "left"),
-        " of ",
-        path.call(print, "right"),
-        ")",
-        adjustClause(path.call(print, "body"), options)
-      ]);
     case "ForAwaitStatement":
+      // Babylon 7 removed ForAwaitStatement in favor of ForOfStatement 
+      // with `"await": true`:
+      // https://github.com/estree/estree/pull/138
+      const isAwait = (n.type === "ForAwaitStatement" || n.await);
+
       return concat([
-        "for await (",
+        "for",
+        isAwait ? " await" : "",
+        " (",
         path.call(print, "left"),
         " of ",
         path.call(print, "right"),
         ")",
         adjustClause(path.call(print, "body"), options)
       ]);
+
     case "DoWhileStatement":
       var clause = adjustClause(path.call(print, "body"), options);
       var doBody = concat(["do", clause]);

tests/flow/async_iteration/__snapshots__/jsfmt.spec.js.snap

@@ -57,6 +57,63 @@ async function* delegate_return() {
 "
 `;
 
+exports[`delegate_yield.js 2`] = `
+"async function *delegate_next() {
+  async function *inner() {
+    var x: void = yield; // error: number ~> void
+  }
+  yield *inner();
+}
+delegate_next().next(0);
+
+async function *delegate_yield() {
+  async function *inner() {
+    yield 0;
+  }
+  yield *inner();
+}
+(async () => {
+  for await (const x of delegate_yield()) {
+    (x: void); // error: number ~> void
+  }
+});
+
+async function *delegate_return() {
+  async function *inner() {
+    return 0;
+  }
+  var x: void = yield *inner(); // error: number ~> void
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+async function* delegate_next() {
+  async function* inner() {
+    var x: void = yield; // error: number ~> void
+  }
+  yield* inner();
+}
+delegate_next().next(0);
+
+async function* delegate_yield() {
+  async function* inner() {
+    yield 0;
+  }
+  yield* inner();
+}
+async () => {
+  for await (const x of delegate_yield()) {
+    (x: void); // error: number ~> void
+  }
+};
+
+async function* delegate_return() {
+  async function* inner() {
+    return 0;
+  }
+  var x: void = yield* inner(); // error: number ~> void
+}
+"
+`;
+
 exports[`generator.js 1`] = `
 "declare interface File {
   readLine(): Promise<string>;
@@ -112,6 +169,61 @@ async function f() {
 "
 `;
 
+exports[`generator.js 2`] = `
+"declare interface File {
+  readLine(): Promise<string>;
+  close(): void;
+  EOF: boolean;
+}
+
+declare function fileOpen(path: string): Promise<File>;
+
+async function* readLines(path) {
+  let file: File = await fileOpen(path);
+
+  try {
+    while (!file.EOF) {
+      yield await file.readLine();
+    }
+  } finally {
+    file.close();
+  }
+}
+
+async function f() {
+  for await (const line of readLines(\\"/path/to/file\\")) {
+    (line: void); // error: string ~> void
+  }
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+declare interface File {
+  readLine(): Promise<string>,
+  close(): void,
+  EOF: boolean
+}
+
+declare function fileOpen(path: string): Promise<File>;
+
+async function* readLines(path) {
+  let file: File = await fileOpen(path);
+
+  try {
+    while (!file.EOF) {
+      yield await file.readLine();
+    }
+  } finally {
+    file.close();
+  }
+}
+
+async function f() {
+  for await (const line of readLines(\\"/path/to/file\\")) {
+    (line: void); // error: string ~> void
+  }
+}
+"
+`;
+
 exports[`return.js 1`] = `
 "declare var gen: AsyncGenerator<void,string,void>;
 
@@ -161,6 +273,55 @@ refuse_return().return(\\"string\\").then(result => {
 "
 `;
 
+exports[`return.js 2`] = `
+"declare var gen: AsyncGenerator<void,string,void>;
+
+// You can pass whatever you like to return, it doesn't need to be related to
+// the AsyncGenerator's return type
+gen.return(0).then(result => {
+  (result.value: void); // error: string | number ~> void
+});
+
+// However, a generator can \\"refuse\\" the return by catching an exception and
+// yielding or returning internally.
+async function *refuse_return() {
+  try {
+    yield 1;
+  } finally {
+    return 0;
+  }
+}
+refuse_return().return(\\"string\\").then(result => {
+  if (result.done) {
+    (result.value: string); // error: number | void ~> string
+  }
+});
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+declare var gen: AsyncGenerator<void, string, void>;
+
+// You can pass whatever you like to return, it doesn't need to be related to
+// the AsyncGenerator's return type
+gen.return(0).then(result => {
+  (result.value: void); // error: string | number ~> void
+});
+
+// However, a generator can \\"refuse\\" the return by catching an exception and
+// yielding or returning internally.
+async function* refuse_return() {
+  try {
+    yield 1;
+  } finally {
+    return 0;
+  }
+}
+refuse_return().return(\\"string\\").then(result => {
+  if (result.done) {
+    (result.value: string); // error: number | void ~> string
+  }
+});
+"
+`;
+
 exports[`throw.js 1`] = `
 "async function *catch_return() {
   try {
@@ -229,3 +390,72 @@ async () => {
 };
 "
 `;
+
+exports[`throw.js 2`] = `
+"async function *catch_return() {
+  try {
+    yield 0;
+  } catch (e) {
+    return e;
+  }
+}
+
+(async () => {
+  catch_return().throw(\\"\\").then(({value}) => {
+    if (value !== undefined) {
+      (value: void); // error: number ~> void
+    }
+  });
+});
+
+async function *yield_return() {
+  try {
+    yield 0;
+    return;
+  } catch (e) {
+    yield e;
+  }
+}
+
+(async () => {
+  yield_return().throw(\\"\\").then(({value}) => {
+    if (value !== undefined) {
+      (value: void); // error: number ~> void
+    }
+  });
+});
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+async function* catch_return() {
+  try {
+    yield 0;
+  } catch (e) {
+    return e;
+  }
+}
+
+async () => {
+  catch_return().throw(\\"\\").then(({ value }) => {
+    if (value !== undefined) {
+      (value: void); // error: number ~> void
+    }
+  });
+};
+
+async function* yield_return() {
+  try {
+    yield 0;
+    return;
+  } catch (e) {
+    yield e;
+  }
+}
+
+async () => {
+  yield_return().throw(\\"\\").then(({ value }) => {
+    if (value !== undefined) {
+      (value: void); // error: number ~> void
+    }
+  });
+};
+"
+`;

tests/flow/async_iteration/jsfmt.spec.js

@@ -1 +1,2 @@
 run_spec(__dirname);
+run_spec(__dirname, { parser: 'babylon' });