TypeScript 4.9+ 'satisfies' operator: validate type conformity without widening literal types

The 'satisfies' operator allows developers to validate that the type of an expression matches some type, without changing the resulting type of that expression.

💡 Verified Solution

Use 'const palette = { ... } satisfies Record<string, string | number>' instead of explicit type annotation.

Patch / Unified Code Diff:

--- old.ts
+++ new.ts
@@ -1,2 +1,2 @@
-const colors: Record<string, string | number[]> = { red: '#f00' };
+const colors = { red: '#f00' } satisfies Record<string, string | number[]>;

Official Primary Reference: https://devblogs.microsoft.com/typescript/announcing-typescript-4-9/#the-satisfies-operator

🧪 Sandbox Execution Evidence

Exit Code: 0

Tests Passed: 1 / 1

Confidence: 95%

Protocol: MCP 2026

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