Debugging & Errors
$definetype-error--plain-english
TLDRThe compiler refusing a shape it did not agree to.
A type error is a bouncer reading the guest list.
You promised user.email is a string. You handed it undefined. The build dies on your laptop instead of on a judge's phone. That is the whole point of TypeScript in this stack.
A type is a label on a box: string, number, boolean, this exact shape of user. The compiler checks whether the thing you are pouring matches the label. A type error is that check saying no.
The classics at 2 a.m.:
"12" + 1 because an input stayed text.id on nullIt feels like the project exploding. It is the opposite. It is the club catching a fake ID before anyone sits down.
Read the first red line
Half of "it won't compile" is this. Fix the shape, not the symptom. The shape lives in a schema — Zod, your ORM models, the type the API already published. as any is a fake ID. It works until the club burns.
A test that expects the right type is a second bouncer. The compiler is the first.
Agents love to skip the door
When an agent writes a pile of code and the CLI bun run build goes red, do not say "fix it." Paste the first type error. The file, the line, the expected vs actual. That is a diagnosis. "Types are broken" is a weather report, and the model will invent a cast.
If the builder gave you TypeScript, use the gift. A red squiggle on your machine is cheaper than a silent undefined on stage.
What this unlocks
A type error is not your project breaking. It is the labels working. Let them complain early. Spend the complaint budget on the product.