EC
TS5086
TypeScriptERRORNotableConfigHIGH confidence

A labeled tuple element is declared as optional with a question mark after th...

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS5086): A labeled tuple element is declared as optional with a question mark after the name and before the colon, rather than after the type.. This diagnostic is emitted by the TypeScript compiler when a labeled tuple element is declared as optional with a question mark after the name and before the colon, rather than after the type..

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

TypeScript compiler reports TS5086 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS5086
// A labeled tuple element is declared as optional with a question mark after the name and before the colon, rather than after the type.

expected output

error TS5086: A labeled tuple element is declared as optional with a question mark after the name and before the colon, rather than after the type.

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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