flow like the river

BACK_BACK/node_modules/graphql/jsutils/invariant.js.flow

@@ -0,0 +1,10 @@
+// @flow strict
+export default function invariant(condition: mixed, message?: string): void {
+  const booleanCondition = Boolean(condition);
+  // istanbul ignore else (See transformation done in './resources/inlineInvariant.js')
+  if (!booleanCondition) {
+    throw new Error(
+      message != null ? message : 'Unexpected invariant triggered.',
+    );
+  }
+}