Add error message for paring unnamed params

Summary:
We're currently not supporting this kind of params

```
+sample(string):void
````

and here's special exception for it.

Reviewed By: RSNara

Differential Revision: D16708583

fbshipit-source-id: 809f9808b77108857c8363536b896089e9cb957f

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

@@ -110,6 +110,31 @@ export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
 
 `;
 
+const NATIVE_MODULES_WITH_UNNAMED_PARAMS = `
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+'use strict';
+
+import type {TurboModule} from '../RCTExport';
+import * as TurboModuleRegistry from '../TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +getBool: (boolean) => boolean;
+
+}
+
+export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+
+`;
+
 const NATIVE_MODULES_WITH_PROMISE_WITHOUT_TYPE = `
 /**
  * Copyright (c) Facebook, Inc. and its affiliates.
@@ -186,6 +211,7 @@ export interface Spec2 extends TurboModule {
 
 module.exports = {
   NATIVE_MODULES_WITH_READ_ONLY_OBJECT_NO_TYPE_FOR_CONTENT,
+  NATIVE_MODULES_WITH_UNNAMED_PARAMS,
   NATIVE_MODULES_WITH_PROMISE_WITHOUT_TYPE,
   NATIVE_MODULES_WITH_ARRAY_WITH_NO_TYPE_FOR_CONTENT_AS_PARAM,
   NATIVE_MODULES_WITH_ARRAY_WITH_NO_TYPE_FOR_CONTENT,

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

@@ -10,6 +10,8 @@ exports[`RN Codegen Flow Parser Fails with error message NATIVE_MODULES_WITH_PRO
 
 exports[`RN Codegen Flow Parser Fails with error message NATIVE_MODULES_WITH_READ_ONLY_OBJECT_NO_TYPE_FOR_CONTENT 1`] = `"Unsupported param for method \\"getString\\", param \\"arg\\". No type specified for $ReadOnly"`;
 
+exports[`RN Codegen Flow Parser Fails with error message NATIVE_MODULES_WITH_UNNAMED_PARAMS 1`] = `"Unsupported type for getBool. Please provide a name for every parameter."`;
+
 exports[`RN Codegen Flow Parser Fails with error message TWO_NATIVE_EXTENDING_TURBO_MODULE 1`] = `"Found two types extending \\"TurboModule\\" is one file. Split them into separated files."`;
 
 exports[`RN Codegen Flow Parser Fails with error message TWO_NATIVE_MODULES_EXPORTED_WITH_DEFAULT 1`] = `

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

@@ -34,7 +34,11 @@ function getObjectProperties(
     let optional = objectTypeProperty.optional;
     let value = objectTypeProperty.value;
     if (value.type === 'NullableTypeAnnotation') {
-      optional = true;
+      if (
+        objectTypeProperty.value.typeAnnotation.type !== 'StringTypeAnnotation'
+      ) {
+        optional = true;
+      }
       value = objectTypeProperty.value.typeAnnotation;
     }
     return {
@@ -145,6 +149,11 @@ function getTypeAnnotationForParam(
   types: TypeMap,
 ): FunctionTypeAnnotationParam {
   let param = paramAnnotation;
+  if (param.name === null) {
+    throw new Error(
+      `Unsupported type for ${name}. Please provide a name for every parameter.`,
+    );
+  }
   let paramName = param.name.name;
   let nullable = false;
   if (param.typeAnnotation.type === 'NullableTypeAnnotation') {