EC
TS2677
TypeScriptERRORNotableTypeHIGH confidence

A type predicate's type must be assignable to its parameter's type.

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2677): A type predicate's type must be assignable to its parameter's type.. This diagnostic is emitted by the TypeScript compiler when a type predicate's type must be assignable to its parameter's 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 TS2677 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2677
// A type predicate's type must be assignable to its parameter's type.

expected output

error TS2677: A type predicate's type must be assignable to its parameter's type.

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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