Some IDEs provide code templates, where you type some abbreviation that expands into a corresponding code construct with placeholders, followed by having you fi

Some IDEs provide code templates, where you type some abbreviation that expands into a corresponding code construct with placeholders, followed by having you fill out the placeholders (jumping from one to the next with Tab). The important part here is that the placeholders’ tab order doesn’t need to be from left to right, so in TFA’s example you could have an order like {3} for {2} in {1} which would give you code completion for {3} based on the {1} and {2} that would be filled in first. There is generally a trade-off between syntax that is nice to read vs. nice to type, and I’m a fan of having nice-to-read syntax out of the box (i.e. not requiring tool support) at the cost of having to use tooling to also make it nice to type. This is not meant as an argument for the above for-in syntax, but as an argument that left-to-right typing isn’t a strict necessity.