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ES6 destructuring (most of it) as macros
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// ES6 destructuring as sweet.js macros. See bottom for examples. | |
// TODO: | |
// elision: var [,,,four] = arr; | |
// rest: var [foo, bar, ...rst] = arr; | |
// function args: function(foo, bar, { baz, poop }) {} | |
macro destruct__objassign { | |
rule { $declare ($prop:ident : $pattern:expr = $default:expr) $obj:expr } => { | |
next $declare ($obj.$prop || $default) $pattern | |
} | |
rule { $declare ($id:ident = $default:expr) $obj:expr } => { | |
next $declare ($obj.$id || $default) $id | |
} | |
rule { $declare ($prop:ident : $pattern:expr) $obj:expr } => { | |
next $declare ($obj.$prop) $pattern | |
} | |
rule { $declare ($name:ident) $obj:expr } => { | |
next $declare ($obj.$name) $name | |
} | |
} | |
macro destruct__arrassign { | |
rule { $declare ($pattern:expr = $default:expr) $obj:expr } => { | |
next $declare ($obj || $default) $pattern | |
} | |
rule { $declare ($pattern:expr) $obj:expr } => { | |
next $declare ($obj) $pattern | |
} | |
} | |
macro finish { | |
rule { $declare { $pattern ... } $obj:expr } => { | |
var obj = $obj; | |
$(destruct__objassign $declare $pattern obj) ... | |
} | |
rule { $declare [ $pattern ... ] $arr:expr } => { | |
var arr = $arr; | |
var i = 0; | |
$(destruct__arrassign $declare $pattern arr[i++]) ... | |
} | |
rule { $declare $id $val:expr } => { | |
$declare $id = $val; | |
} | |
} | |
macro next { | |
// wrap all fields in parentheses | |
rule { $a $b $c ($acc ...), $prop:ident : $pattern:expr = $val:expr } => { | |
next $a $b $c ($acc ... ($prop: $pattern = $val)) | |
} | |
rule { $a $b $c ($acc ...), $prop:ident : $pattern:expr } => { | |
next $a $b $c ($acc ... ($prop: $pattern)) | |
} | |
rule { $a $b $c ($acc ...), $name:ident = $val:expr } => { | |
next $a $b $c ($acc ... ($name = $val)) | |
} | |
rule { $a $b $c ($acc ...), $pattern:expr } => { | |
next $a $b $c ($acc ... ($pattern)) | |
} | |
// pass along normalized object | |
rule { $declare ($obj:expr) {} ($acc ...) } => { | |
finish $declare { $acc ... } $obj | |
} | |
rule { $declare ($obj:expr) [] ($acc ...) } => { | |
finish $declare [ $acc ... ] $obj | |
} | |
// strip out fields | |
rule { $declare $o { $field ... } } => { | |
next $declare $o {} (), $field ... | |
} | |
rule { $declare $o [ $field ... ] } => { | |
next $declare $o [] (), $field ... | |
} | |
// pass normal expr along | |
rule { $declare ($obj:expr) $var:expr } => { | |
finish $declare $var $obj | |
} | |
} | |
let var = macro { | |
rule { $var:expr = $obj:expr } => { | |
next var ($obj) $var | |
} | |
} | |
let let = macro { | |
rule { $id = macro { $body ... } } => { | |
let $id = macro { $body ... } | |
} | |
rule { $var:expr = $obj:expr } => { | |
next let ($obj) $var | |
} | |
} | |
let const = macro { | |
rule { $var:expr = $obj:expr } => { | |
next const ($obj) $var | |
} | |
} | |
// examples: | |
var {one, two} = { one: 1, two: 2 }; | |
var [one, two] = [1, 2]; | |
// renaming | |
var { one: val1 } = { one: 1, two: 2 }; | |
// default values | |
var {one = 1, two} = obj; | |
var [one, two = 2] = arr; | |
// multiple levels of destructuring | |
var [one, {two, three}] = [1, { two: 2, three: 3 }]; | |
var [one, {two, nums: [three, four]}] = [1, { two: 2, nums: [3, 4] }]; | |
// default values deep down | |
var [one, {two, three = 3000}] = [1, { two: 2, three: 3 }]; | |
// let and const | |
let { one, two } = obj; | |
const { one, two } = obj; |
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