EC
TS6199
TypeScriptERRORNotableConfigHIGH confidence

All variables are unused.

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS6199): All variables are unused.. This diagnostic is emitted by the TypeScript compiler when all variables are unused..

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

TypeScript compiler reports TS6199 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS6199
// All variables are unused.

expected output

error TS6199: All variables are unused.

Fix

Fix the tsconfig.json option

WHEN When a compiler option is invalid or missing

Fix the tsconfig.json option
// tsconfig.json
{
  "compilerOptions": {
    // Review and correct the flagged option
  }
}
// Run: npx tsc --showConfig to see effective config

Why this works

TypeScript validates tsconfig.json options; check the official tsconfig reference for valid values.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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