EC
TS1547
TypeScriptERRORNotableSyntaxHIGH confidence

'using' declarations are not allowed in 'case' or 'default' clauses unless co...

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1547): 'using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block.. This diagnostic is emitted by the TypeScript compiler when 'using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block..

Why it happens
  1. 1Incorrect TypeScript syntax or type usage
  2. 2Type mismatch between declared and actual value
How to reproduce

TypeScript compiler reports TS1547 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1547
// 'using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block.

expected output

error TS1547: 'using' declarations are not allowed in 'case' or 'default' clauses unless contained within a block.

Fix

Address the TypeScript diagnostic

WHEN When this error is reported by the compiler

Address the TypeScript diagnostic
// Run the TypeScript compiler for details:
npx tsc --noEmit
// Use the TypeScript playground to test your code:
// https://www.typescriptlang.org/play

Why this works

Review the full error message and location; the TypeScript handbook provides guidance on each error category.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev

← All TypeScript errors