EC
TS9013
TypeScriptERRORNotableTypeHIGH confidence

Expression type can't be inferred with --isolatedDeclarations.

Production Risk

Build will fail; resolve before shipping.

What this means

A TypeScript diagnostic (TS9013): Expression type can't be inferred with --isolatedDeclarations.. This diagnostic is emitted by the TypeScript compiler when expression type can't be inferred with --isolatedDeclarations..

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

TypeScript compiler reports TS9013 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS9013
// Expression type can't be inferred with --isolatedDeclarations.

expected output

error TS9013: Expression type can't be inferred with --isolatedDeclarations.

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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