excess-property-checking

What problem does it solve? TypeScript flags unknown properties on object literals but silently allows the same extra properties through intermediate variables, causing confusion about why identical code sometimes errors and sometimes passes. This Skill explains the distinction so you stop bypassing the check with type assertions and start catching real typos in property names. ## Core Features & Use Cases - Error Diagnosis: Explains why "Object literal may only specify known properties" appears for literals but disappears with intermediate variables or type assertions. - Typo Detection Guidance: Shows how excess property checking catches misspelled optional properties like darkmode instead of darkMode. - Weak Type Handling: Covers the special check for interfaces with only optional properties, which applies even through variables. - Use Case: You assign a config object to a typed variable and get an "unknown property" error, but the error vanishes when you use an intermediate variable. This Skill explains why and shows the correct fix instead of an unsafe as assertion. ## Quick Start Ask the AI to explain why my TypeScript object literal triggers an excess property error while the same value assigned through a variable does not.