Revert change dropping await on return

Reverses lightscript#23

`return await x` is semantically different from `return x`. The user should be in control of when he wants which semantics, rather than `await` implicitly being dropped.

src/helpers/functions.lsc

@@ -21,10 +21,7 @@ export addImplicitReturns(functionPath) ->
         throw path.buildCodeFrameError("Ambiguous implicit `return` of multiple variables. " +
           "Add an explicit `return` statement on the next line.")
 
-    if expr~isa("AwaitExpression"):
-      t.returnStatement(expr.argument)~atNode(expr)
-    else:
-      t.returnStatement(expr)~atNode(expr)
+    t.returnStatement(expr)~atNode(expr)
 
   transformTails(
     functionPath.get("body")

test/fixtures/arrow-function-expressions/async/expected.js

@@ -1,4 +1,4 @@
 (async function () {
   await 1;
-  return 2;
+  return await 2;
 });

test/fixtures/arrow-function-expressions/fat-async/expected.js

@@ -1,4 +1,4 @@
 async () => {
   await 1;
-  return 2;
+  return await 2;
 };

test/fixtures/arrow-methods-class/fat-async/expected.js

@@ -4,6 +4,6 @@ class A {
   }
 
   async f() {
-    return this;
+    return await this;
   }
 }

test/fixtures/arrow-methods-obj/fat-async/expected.js

@@ -1,5 +1,5 @@
 const o = {
   async f() {
-    return this;
+    return await this;
   } };
 o.f = o.f.bind(o);

test/fixtures/arrow-methods-obj/skinny-async/expected.js

@@ -1,4 +1,4 @@
 const o = {
   async f(x) {
-    return x;
+    return await x;
   } };

test/fixtures/await-arrow/await-array/expected.js

@@ -1,7 +1,7 @@
 async function fn() {
   const x = await Promise.all([p1, p2]);
   const y = await Promise.all([p1, p2]);
-  return Promise.all((() => {
+  return await Promise.all((() => {
     const _arr = [];for (const p of ps) _arr.push(p);return _arr;
   })());
 }

test/fixtures/await-arrow/safe-statement/expected.js

@@ -1,5 +1,5 @@
 async function fn() {
-  return (async () => {
+  return await (async () => {
     try {
       return await fetch();
     } catch (_err) {

test/fixtures/await-arrow/statement/expected.js

@@ -1,3 +1,3 @@
 async function fn() {
-  return fetch();
+  return await fetch();
 }

test/fixtures/named-arrow-functions/async/expected.js

@@ -1,4 +1,4 @@
 async function fn() {
   await 1;
-  return 2;
+  return await 2;
 }

test/fixtures/named-arrow-functions/fat-async/expected.js

@@ -1,4 +1,4 @@
 const fn = async () => {
   await 1;
-  return 2;
+  return await 2;
 };