EC
TS1431
TypeScriptERRORNotableSyntaxHIGH confidence

'for await' loops are only allowed at the top level of a file when that file ...

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1431): 'for await' loops are only allowed at the top level of a file when that file is a module, but this file has no imports or exports. Consider adding an empty 'export {}' to make this file a module.. This diagnostic is emitted by the TypeScript compiler when 'for await' loops are only allowed at the top level of a file when that file is a module, but this file has no imports or exports. Consider adding an empty 'export {}' to make this file a module..

Why it happens
  1. 1await used outside an async function, or async/await return type mismatch
How to reproduce

TypeScript compiler reports TS1431 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1431
// 'for await' loops are only allowed at the top level of a file when that file is a module, but this file has no imports or exports. Consider adding an empty 'export {}' to make this file a module.

expected output

error TS1431: 'for await' loops are only allowed at the top level of a file when that file is a module, but this file has no imports or exports. Consider adding an empty 'export {}' to make this file a module.

Fix

Add 'async' to the containing function

WHEN Using await outside an async function

Add 'async' to the containing function
// Mark the function as async
async function fetchData() {
  const result = await fetch('/api/data');
  return result.json();
}

Why this works

await can only be used inside async functions; the 'async' keyword makes the function return a Promise.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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