If expressions

An if expression chooses between two values:

if input.environment == 'prod' then 3 else 1

Both branches must evaluate to the same type. If the branches have different concrete types, the checker reports a mismatch unless a common type is valid for that position.

For optional types, null checks cause values to be narrowed in the branch they guard. In the example below, input.greeting begins as optional(string) but is a plain string in the else branch.

banner: if input.greeting == null then $'Hello, {{ input.name }}' else input.greeting

For a simple fallback, prefer the ?? operator:

input.tls?.cert ?? 'self-signed'