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Mic92 merged 1 commit into from
Dec 21, 2025
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docs: document older let expression syntax #14843

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21 changes: 21 additions & 0 deletions doc/manual/source/language/syntax.md
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This evaluates to `"foobar"`.

There is also another, older, syntax for let expressions that should not be used in new code:

> *let* = `let` `{` *identifier* = *expr* `;` [ *identifier* = *expr* `;`]... `}`

In this form, the attribute set between the `{` `}` is recursive.

One of the attributes must have the special name `body`,
which is the result of the expression.

Example:

```nix
let {
foo = bar;
bar = "baz";
body = foo;
}
```

This evaluates to "baz".

## Inheriting attributes

When defining an [attribute set](./types.md#type-attrs) or in a [let-expression](#let-expressions) it is often convenient to copy variables from the surrounding lexical scope (e.g., when you want to propagate attributes).
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