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Small syntax decisions

16 November 2025·2 min read

A language is mostly small choices. A few from the prototype: what braces mean, where a line ends, and why `for` cannot name a label.

The big ideas get the posts. A language's daily feel comes from small decisions, made once and lived with forever. Here are some, and why they went the way they did.

{ x } is a block, { x: 1 } is a map

let point = (x: int, y: int = 0) => { x, y }   // a map: two fieldslet same = (x) => { x }                         // a block: it returns x

Braces mean both a block and a map, as in JavaScript. The rule: one bare name is a block, anything with a comma or a colon is a map. It is the reading most people guess, and the checker warns when it may not be.

Lines that continue

let paid = orders    | filter((o) => o.paid)    | map((o) => o.total)

A line that starts with |, ??, &&, ||, ?, :, .method or else carries on the line before. No semicolons, and no trailing operators to remember.

for is a keyword, so labels use field

for loops over lists in code and in markup, so <label for="email"> cannot use it. In views a label's target is field:

<label field="email">Email</label>

An odd word to learn once, rather than a keyword that means two things.

Names are free, until they hide a builtin

A variable may be called max, but then max(...) means the variable in that scope. The checker says so where it happens, because a prop named max quietly breaking a call three lines down is the kind of bug nobody finds by reading.

Since then: these rules are in Quillo's language tour. See Language tour.