Inline Shape Annotations

In Lua you've been using tables as records for a long time: local user = {name = "Ana", age = 20}. Nothing stops you from misspelling a field, forgetting one, or storing a string where a number belongs — you only find out when the code runs.

Luau lets you describe the shape of such a table right in the declaration, listing each field and its type between curly braces:

local user: {name: string, age: number} = {
    name = "Ana",
    age = 20,
}

Compare this with the table types you already know: {number} describes an array and {[string]: number} describes a map with any string keys. A shape is more precise — it names each field individually and gives every field its own type.

Once the shape is declared, the type checker verifies the table against it while you edit. A missing field or a wrong value type is flagged before the code ever runs:

local user: {name: string, age: number} = {
    name = "Ana",
    age = "twenty", -- ✗ type error: string is not a number
}

As always, the annotation adds no runtime behavior — the table is a plain Lua table. Inline shapes are perfect for one-off structures you don't plan to reuse; in the next lesson you'll give shapes a name.