EC
TS2850
TypeScriptERRORNotableTypeHIGH confidence

The initializer of a 'using' declaration must be either an object with a '[Sy...

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2850): The initializer of a 'using' declaration must be either an object with a '[Symbol.dispose]()' method, or be 'null' or 'undefined'.. This diagnostic is emitted by the TypeScript compiler when the initializer of a 'using' declaration must be either an object with a '[Symbol.dispose]()' method, or be 'null' or 'undefined'..

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

TypeScript compiler reports TS2850 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2850
// The initializer of a 'using' declaration must be either an object with a '[Symbol.dispose]()' method, or be 'null' or 'undefined'.

expected output

error TS2850: The initializer of a 'using' declaration must be either an object with a '[Symbol.dispose]()' method, or be 'null' or 'undefined'.

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

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