EC
TS1451
TypeScriptERRORNotableSyntaxHIGH confidence

Private identifiers are only allowed in class bodies and may only be used as ...

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1451): Private identifiers are only allowed in class bodies and may only be used as part of a class member declaration, property access, or on the left-hand-side of an 'in' expression. This diagnostic is emitted by the TypeScript compiler when private identifiers are only allowed in class bodies and may only be used as part of a class member declaration, property access, or on the left-hand-side of an 'in' expression.

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

TypeScript compiler reports TS1451 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1451
// Private identifiers are only allowed in class bodies and may only be used as part of a class member declaration, property access, or on the left-hand-side of an 'in' expression

expected output

error TS1451: Private identifiers are only allowed in class bodies and may only be used as part of a class member declaration, property access, or on the left-hand-side of an 'in' expression

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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