'await using' declarations are not allowed in 'case' or 'default' clauses unl...
Production Risk
Build will fail; resolve before shipping.
A syntax error (TS1548): 'await using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block.. This diagnostic is emitted by the TypeScript compiler when 'await using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block..
- 1await used outside an async function, or async/await return type mismatch
TypeScript compiler reports TS1548 during type checking.
// Triggers TS1548 // 'await using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block.
expected output
error TS1548: 'await using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block.
Fix
Add 'async' to the containing function
WHEN Using await outside an async 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.
TypeScript Compiler Diagnostics
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