fix lint warnings (incl. in generated code)

Author: jjergus

src/RequestParametersCodegenBuilder.hack

@@ -9,6 +9,7 @@
 
 namespace Facebook\HackRouter;
 
+use namespace HH\Lib\C;
 use type Facebook\HackCodegen\{
   CodegenClass,
   CodegenShapeMember,
@@ -43,21 +44,26 @@ final class RequestParametersCodegenBuilder<T as RequestParametersBase>
   protected function getCodegenClass(self::TSpec $spec): CodegenClass {
     $param_builder = $this->parameterBuilder;
     $controller = $spec['controller'];
+    $getParameters = $this->getParameters;
+    $parameters = $getParameters($controller);
+
+    $body = $this->cg->codegenHackBuilder();
 
-    $body = $this->cg
-      ->codegenHackBuilder()
-      ->addAssignment(
+    if (!C\is_empty($parameters)) {
+      // avoid generating an assignment to an unused variable
+      $body->addAssignment(
         '$p',
         '$this->getParameters()',
         HackBuilderValues::literal(),
-      )
+      );
+    }
+
+    $body
       ->addLine('return shape(')
       ->indent();
 
-    $getParameters = $this->getParameters;
     $param_shape = vec[];
-
-    foreach ($getParameters($controller) as $parameter) {
+    foreach ($parameters as $parameter) {
       $param_spec = $parameter['spec'];
       $request_spec = $param_builder::getRequestSpec($param_spec);
       $getter_spec = $request_spec::getGetterSpec($param_spec);

tests/UriMapBuilderTest.hack

@@ -33,7 +33,7 @@ final class UriMapBuilderTest extends \Facebook\HackTest\HackTest {
     $scanned = await FileParser::fromFileAsync(
       __DIR__.'/examples/GetRequestExampleController.hack',
     );
-    $class = $scanned->getClass(GetRequestExampleController::class);
+    $scanned->getClass(GetRequestExampleController::class);
     $builder = $this->getBuilder($scanned);
 
     expect($builder->getUriMap()[HttpMethod::GET]->values())->toBePHPEqual(
@@ -45,7 +45,7 @@ final class UriMapBuilderTest extends \Facebook\HackTest\HackTest {
     $scanned = await FileParser::fromFileAsync(
       __DIR__.'/examples/GetRequestExampleController.hack',
     );
-    $class = $scanned->getClass(GetRequestExampleController::class);
+    $scanned->getClass(GetRequestExampleController::class);
     $builder = $this->getBuilder($scanned);
     $map = $builder->getUriMap();
     expect($map->containsKey(HttpMethod::POST))->toBeFalse(