Allow NativeModule method return types to use type aliases

Summary:
We already support type-aliases in our NativeModule method params. This diff extends the support to NativeModule method returns.

**Note:** I need to see if I need to update the generators to handle this case. Will do that in this diff, after working through other higher priority stuff.

Changelog: [Internal]

Reviewed By: PeteTheHeat

Differential Revision: D22828839

fbshipit-source-id: cf5c756d3cacf067df217cdb6212946320a2d4be

packages/react-native-codegen/src/CodegenSchema.js

@@ -304,6 +304,11 @@ export type FunctionTypeAnnotationReturn =
       nullable: boolean,
       type: 'ObjectTypeAnnotation',
       properties: ?$ReadOnlyArray<ObjectParamTypeAnnotation>,
+    |}>
+  | $ReadOnly<{|
+      nullable: boolean,
+      type: 'TypeAliasTypeAnnotation',
+      name: string,
     |}>;
 
 export type FunctionTypeAnnotationReturnArrayElementType =

packages/react-native-codegen/src/parsers/flow/modules/__test_fixtures__/fixtures.js

@@ -200,7 +200,7 @@ type Foo = {|
 
 export interface Spec extends TurboModule {
   // Exported methods.
-  foo1: (x: Foo) => void;
+  foo1: (x: Foo) => Foo;
   foo2: (x: Foo) => void;
 }
 

packages/react-native-codegen/src/parsers/flow/modules/__tests__/__snapshots__/module-parser-test.js.snap

@@ -940,8 +940,9 @@ Object {
                   },
                 ],
                 "returnTypeAnnotation": Object {
+                  "name": "Foo",
                   "nullable": false,
-                  "type": "VoidTypeAnnotation",
+                  "type": "TypeAliasTypeAnnotation",
                 },
                 "type": "FunctionTypeAnnotation",
               },

packages/react-native-codegen/src/parsers/flow/modules/methods.js

@@ -244,6 +244,13 @@ function getReturnTypeAnnotation(
         );
       }
     case 'ObjectTypeAnnotation':
+      if (returnType.type === 'GenericTypeAnnotation') {
+        return {
+          nullable,
+          type: 'TypeAliasTypeAnnotation',
+          name: returnType.id.name,
+        };
+      }
       return {
         nullable,
         type: 'ObjectTypeAnnotation',
@@ -323,7 +330,7 @@ function buildMethodSchema(
 
   const returnTypeAnnotation = getReturnTypeAnnotation(
     name,
-    getValueFromTypes(value.returnType, types),
+    value.returnType,
     types,
   );
   return {