EC
TS6420
TypeScriptERRORNotableConfigHIGH confidence

Project 'X' is out of date because X.

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS6420): Project 'X' is out of date because X.. This diagnostic is emitted by the TypeScript compiler when project 'X' is out of date because X..

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

TypeScript compiler reports TS6420 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS6420
// Project 'X' is out of date because X.

expected output

error TS6420: Project 'X' is out of date because X.

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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