Pre-pre-RFC: syntactic sugar for `Default::default()`

[CAD97]

@scottmcm

EDIT: Or, less seriously, it could desugar to

fn Foo(_0: i32, _1: i32, RangeFull: RangeFull) -> Foo { Foo { 0: _0, 1: _1, .. } }

so you'd need to call it as Foo(13, 42, ..)

Why not just go all the way then

#[allow(non_upper_case_globals)]
static Foo: FooConstructor = FooConstructor;
#[derive(Copy, Clone)]
struct FooConstructor;

impl FnOnce<(i32, i32, RangeFull)> for FooConstructor {
    type Output = Foo;
    extern "rust-call" fn call_once(self, (_0, _1, ..): (i32, i32, RangeFull)) -> Foo {
        Foo { _0, _1, _2: 4, _3: 5 }
    }
}

impl FnOnce<(i32, i32, i32, RangeFull)> for FooConstructor {
    type Output = Foo;
    extern "rust-call" fn call_once(self, (_0, _1, _2, ..): (i32, i32, i32, RangeFull)) -> Foo {
        Foo { _0, _1, _2, _3: 5 }
    }
}

impl FnOnce<(i32, i32, i32, i32)> for FooConstructor {
    type Output = Foo;
    extern "rust-call" fn call_once(self, (_0, _1, _2, _3): (i32, i32, i32, i32)) -> Foo {
        Foo { _0, _1, _2, _3 }
    }
}

fn main() {
    dbg!(Foo(0, 1, ..));
    dbg!(Foo(0, 1, 2, ..));
    dbg!(Foo(0, 1, 2, 3));
}