Spread operator (...)

[tmteam]

Spread operator ...

Four usage contexts:

1. Variadic function params (rest)

fun foo(a, b, ...c)          # c: T[] — captures remaining args
fun foo(a, b, ...c:int[])    # with explicit type

...c must be the last parameter. Type is array.

2. Array spread

x = [1,2,3]
y = [4,5,6]
z = [...x, ...y]             # [1,2,3,4,5,6]

Expands array inside array literal. Element types must be compatible.

3. Function call spread

foo(1, 2, ...z)              # z: int[] → expanded into individual arguments

Passes array elements as individual arguments. Binds to variadic parameter.

4. Struct spread

user = { name: 'Masha', age: 14 }
copy = { ...user }           # shallow copy
merged = { ...user, age: 15 } # field override

Copies struct fields. Fields after spread override earlier ones.

Implementation areas

• Tokenizer — new TokType.Spread (...)
• Parser — spread in array literal, function call, struct literal, param declarations
• TIC — variadic params, spread type propagation
• Runtime — array concat, struct merge, rest arg collection
• Errors — spread of non-array in array context, spread of non-struct in struct context, rest param must be last

[tmteam]

# candidate for inheritance 

type user = { 
    name:text
    age:int 
}

type customer = { ...user
    id:long
    comment:text
}